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09/12/2018

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ANATOMY AND PHYSIOLOGY OF BONE

BENIGN BONE TUMORS

MALIGNANT BONE TUMORS

BENIGN SOFT TISSUE TUMORS

MALIGNANT SOFT TISSUE TUMORS

PEDIATRIC SYNDROMES

CONFERENCES/ARTICLES

BOARD REVIEW QUESTIONS

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PATHOLOGY JOBS

BONE PRODUCING TUMORS

OSTEOBLASTOMA
Definition:
- Benign bone forming neoplasm producing woven bone
spicules bordered by prominent osteoblasts (osteoid
osteoma measuring more than 2.0 cm)
Epdemiology:
- About 1% of bone tumors
- Age: 10-30 y/o ( male teenagers)
- Male:Female ratio 2.5:1,
Sites of involvement:
- Predilection for the spine (40-55% of cases)
- Other common sites femur and proximal tibia
- Cementoblastoma of jaw is considered osteoblastoma
and is attached to the root of tooth.
Clinical findings:
- Osteoblastoma of spine may cause back pain, scoliosis
and nerve root compression.
- Jaw lesion may produce tooth pain.
- Aspirin does not relieve pain after long therapy.
Imaging:
- Lytic well circumscribed oval or round defect
-Almost always confined by a periosteal shell of reactive
bone.
Gross:
-Red or red brown (vascular).
- Often with gritty or sandpaper consistency.
Histopathology:
-Composed of woven bone spicules or trabeculae lined by
a single layer of osteoblasts.
- Stromal rich vascularity.
- Scattered osteoclast-type multinucleated giant cells are
often present.
- Focal blood filled spaces mimicking Aneurysmal Bone
Cyst (ABC) may be present.
- Osteoblastomas do not infiltrate and isolate pre-existing
lamellar bone structures as does osteosarcoma.
Prognosis:
- Excellent
- Recurrences unusual if well excisded

PRIMARY BONE CYSTS
SIMPLE (UNICAMERAL ) BONE CYST (UBC)
Definition:
- Intramedullary, usually unilocular, bone cyst filled with
serous or sero-sanguineous fluid.
Epidemiology:
-85% of patients in the first decades of life.
- Male:Female ratio 3:1.
Sites of involvement:
Most common locations:
-proximal humerus
-proximal femur
-proximal tibia
Clinical findings:
-Pain and swelling.
-Patients may present with pathological fracture.
Imaging:
-Well demarcated and radiolucent.
-Typically begins in the metaphysis and extends into the
diaphysis.
Gross:
-Fragments of thin whitish membrane
-Usually during surgery you get scant tissue material.
Histopathology:
- Cyst wall consist of a thin layer of fibrous tissue
composed of scattered fibroblasts and collagen
fibers,.
-No cell lining of cystic internal surface.
-Pathologic fractures may cause reactive changes and
show numerous reactive fibroblasts, osteoclast type
giant cells, hemosiderin deposists and reactive woven
bone.
Genetics:
- Rearrangements involving chromosomes 4, 6, 8, 16, 21.
Prognosis:
-Recurrence is reported at 10-20% of cases, especially in
children.
-Growth arrest of the affected bone and avascular
necrosis of the head of the femur after pathological
fracture can occur

ANEURYSMAL BONE CYST (ABC)
Definition:
- Benign multiloculated , blood-filled cystic mass that is
often expansile and destructive.
Epidemiology:
- Affects all age groups but generally occurs during the
first two decades of life (median age approximately
13 years).
- No s*x predilection.
Sites of involvement:
-May affect any bone.
-Usually arise in the metaphysis of long bone especially
the femur, tibia and humerus.
Clinical findings:
- Pain and swelling which may be secondary to fracture.
Imaging:
- Usually eccentric, expansile lesion with well defined
margins.
- Most lesions are completely lytic and often contain a
thin shell of reactive bone at the periphery.
- CT and MRI may demonstrate internal septa and
characteristic fluid-fluid level.
Gross:
- Well-defined sponge-like mass.
- Composed of multiple, blood filled spaces separated by
thin, tan-white septa.
Histopathology:
- Walls of ABC consist of plump uniform fibroblaststs
( which may be mitotically active), multinucleated
osteoclast-like giant cells ( sometimes they look like
jumping into swimming pool cystic spaces), and thin
trabeculae of reactive woven bone.
-Surface of reactive woven bone is lined by plump
osteoblasts.
- 1/3 of cases contain a cartilage-like matrix, called 'blue
bone', which is not common in other bone lesions.
- Necrosis is uncommon unless there has been a
previous pathologic fracture.
Genetics:
- Rearrangements of chromosome 17q13.
Prognosis:
- Recurrence rate following curretage is variable
(20-70%).
- Primary aneurysmal bone cysts account for
approximately 70% of all cases.
- Majority of secondary ABC arise in association
with benign neoplasms, most commonly giant
cell tumor of bone (GCT), chondroblastoma,
osteoblastoma, and fibrous dysplasia, and less
frequently, osteosarcoma.

FIBRO-OSSEOUS TUMORS
FIBROUS DYSPLASIA
Definition:
-Benign medullary fibro-osseous lesion which may involve
one (monostotic) or more bones (polyostotic).
Epidemiology:
-Children and adults
-Monostotic solitary lesion most common 70-80%
-No s*x predilection.
Sites of involvement:
-Gnathic (jaw) bones most common
-Long bones are more often involved in woman
-Ribs and skull are favored sites for man.
-Monostotic form, about 35% involve the head, 1/3 tibia and
femur, and rest 20% ribs.
-Polyoostotic form, the femur, pelvis and tibia are more
common involved
Clinical findings:
-Fibrous dysplasia may present in monostotic or polyostotic
form.
-Polyostotic form can be confined to one extremity or one
side of the body or be diffuse.
-Polyostotic form often manifest earlier in life than the
monostotic form.
-FD is often asymptomatic but pain and fractures may be
part of clinical spectrum.
-FD may be associated with oncogenic osteomalacia.
-FD may be associated with McCune-Albright syndrome, in
which there are endocrine abnormalities and skin
pigmentation.
Imaging:
-Non agressive geographical lesion with a ground glass
matrix.
-In the appendicular skeleton, the margins are usually well
defined and surrounded by a rim of sclerotic bone.
-FD in the craniofacial skeleton seems to be less well
defined and blends with surrounding bone.
Gross:
-Well circumscribed
-Gritty and leather-like consistency.
Histopathology:
-Composed of cellular fibrous tissue surrounding irregular,
curvilinear bony trabeculae.
-The bony trabeculae are discontinuous and are composed
of woven bone that is formed directly from the spindle cells
with minimal osteoblastic ri***ng.
- In craniofacial tumors, the lesional bone tends to fuse with
the surrounding host cancellous bone, explaining the lack
of demarcation radiographically.
-The spindle cells may be arranged in a storiform pattern,
and may be associated with collectioon of foamy
macrophages mimicking a xanthoma or fibroxanthoma.
-Collagen fibers (Sharpey-like fibers) are frquently seen
extending from the fibrous tissue ibnto the lesional bone.
-Cystic changes mimicking ABC are occasionally
encountered.
Genetics:
- Mutation of the G protein (guanine nucleotide-binding
protein).
Prognosis:
- Good.
- Therapy ranges from observation to surgical removal.

OSTEOFIBROUS DYSPLASIA
Definition:
-Self-limited benign fibro-osseous lesion of bone.
-Involving cortical bone of the anterior mid-shaft of the tibia
during infancy and childhood.
Epidemiology:
-Rare tumor that accounts for less than 1% of all bone
tumors.
- Commonly seen in boys during the first two decades of
life with precipitous drop-off thereafter.
Sites of involvement:
-Proximal or middle-third of the tibia is the most frequent
(90%)
-Less common sites are ulna and radius.
Clinical findings:
-Rare after the age of 15.
-Most common presenting symptoms are swelling or
painless deforming (bowing) of the involved segment of
the limb.
Imaging:
-Well-delineated, intracortical lucency, surrounded by
areas of sclerosis.
-May form as a single lytic lesion, but more commonly
forms confluent oval-shaped, scalloped, saw-toothed or
bubbly multiloculated lytic lesions in cortex.
Gross:
-Varies in size from 10cm.
-Typically solid, yellow or white and gritty, and confined to
the cortex, which is expanded and attenuated.
Histopathology:
-Composed of irregular curvilinear trabeculae of woven
bone that at the periphery merge with pre-existing
cancellous bone.
-Trabeculae of woven bone are rimmed by prominent
osteoblasts and scattered osteoclasts may be seen.
-intervening stroma is composed of benign appearing
spindle-shaped cells embedded in a collagenous matrix.
-Isolate single stromal cells may express keratin; however,
clusters of epithelial cells, as seen in well differentiated
adamantinoma are absent.
Immunohistochemistry:
- Positive for vimentin, occasionally S100 and Leu7.
Genetics:
- Trisomy 7 and 8 have been demonstrated.
Prognosis:
-Natural history of osteofibrous dysplasia is that of gradual
growth during the first decade of life with stabilization at
about 15 years of age resolution.
-Progression of OFD-like adamantinoma to classic
adamantinoma has been shown in few patients.

FIBROUS TUMORS
FIBROUS CORTICAL DEFECT/NON-OSSIFYING FIBROMA
Definition:
-Benign lesion of bone composed of spindle-shaped
fibroblasts, arranged in a storiform pattern, with a variable
admixture of multinucleated osteoclast-like giant cells.
- Foamy cells (xanthoma), chronic inflammatory cells and
hemosiderin may be present
-The name fibrous cortical defect is used when the lesion
is confined to the cortex; however if becomes large
enough to extend into adjacent medullary cavity than the
term non-ossifying fibroma is used.
Epidemiology:
-Patient have ranged in age from 6 to 74 years old. 30-40%
in children.
-An average age of 4 years 54% of boys and 22% of girls,
had a lesion involving the cortex, and most regressed
spontaneously over a period of approximately 2.5 years.
Site of involvement:
-Approximately 40% of NOF occur in the long bones, with
distal femur, distal and proximal tibia most frequently
involved.
- As many as 25% of cases involve the pelvic bone, in
particular the ilium.
Clinical findings:
-Majority of NOF cases are asymptomatic, and are an
incidental discovery on X-rays performed for other reasons.
-Larger lesion may cause pain that is probably secondary
to microfractures or obvious pathologic fracture.
-Most pathologic fractures develop through lesions that
involve more than 50% of the diameter of the bone.
-The vast majority of NOF are single, although thay are
multiple in 8% of cases.
-Multiple NOF may be associated with syndromes such as
neurofibromatosis and Jaffe-Campanacci syndrome.
Imaging:
-Eccentric, lytic lesions centered within the metaphyseal
cortex and adjacent medullary cavity of long tubular bones.
-Well demarcated with sclerotic margins and frequently
harbor internal trabeculation.
Gross:
-Eccentric, well circumscribed and have sclerotic borders.
-The overlying cortex is thinned and may be completely
eroded.
-The lesions are tan brown and frequently have areas that
are soft and yellow.
Histopathology:
-Stroma of spindle-shaped fibroblasts, arranged , at least
focally, in a whorled, storiform pattern,among which
variable number of small, multinucleated, osteclast-type
giant cells are scattered.
-Foam (xanthoma) cells, with small, dark nuclei are
frequently, but not always found interpersed among the
stromal cells individually, or in small clusters.
-Scattered inflammatory cells, mainly lymphocytes, are
present.
- Small stromal hemorrhages and hemosiderin may be
present.
Prognosis:
-Excellent.
-Asymptomatic NOF usually do not need surgical excision.
-Painful larger lesions or those that have an impending or
established pathologic fracture are adequately treated by
curretage.

BENIGN BONE TUMORS
BONE PRODUCING TUMORS
- OSTEOID OSTEOMA
- OSTEOBLASTOMA
PRIMARY BONE CYSTS
- SIMPLE (UNICAMERAL) BONE CYST
- ANEURYSMAL BONE CYST (ABC)
FIBRO-OSSEOUS TUMORS
- FIBROUS DYSPLASIA
- OSTEOFIBROUS DYSPLASIA
FIBROUS TUMORS
- FIBROUS CORTICAL DEFECT AND
NON-OSSIFYING FIBROMA
- MYOFIBROMA
- DESMOPLASTIC FIBROMA
CARTILAGE TUMORS
- CHEST WALL HAMARTOMA/CHONDROMATOUS HAMARTOMA OF THE CHEST WALL
- OSTEOCHONDROMA (EXOSTOSIS)
- ENCHONDROMA
- CHONDROBLASTOMA
GIANT CELL TUMOR
OTHER LESION
- LANGERHANS CELL HISTIOCYTOSIS (EOSINOPHILIC GRANULOMA) OF BONE
- ROSAI-DORFMAN DISEASE
- HEMANGIOMA OF BONE
- OSTEOMYELITIS
-

REFERENCES:
WHO Pathology and Genetics of Tumors of Soft Tissue and Bone, Lyon: IARC Press, 2002
Dorfman H. D., Bone Tumors, New York: Mosby, 1998
Potter's, Pathology of the fetus, infant and child, Mosby/Elsevier 2007
Weiss W.S., Soft Tissue Tumors, Mosby/Elsevier 2008

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MYOFIBROMA
Definition:
-Myofibroma and myofibromatosis are terms used to
denote the solitary (myofibroma) and multicentric
(myofibromatosis) occurence of benign neoplasms
composed of contractile myoid cells arranged around
thin-walled blood vessels.
- Myofibroma(tosis) forms a morphological continuum
with myopericytoma and so-called infantile.
hemangiopericytoma.
Epidemiology:
-Myofibroma of bone affects very young children and
many patients first develop lesions in utero.
-Many cases are detected at birth or within first two
years of life.
-Male predominance.
Sites of involvement:
-Commonly involve the skull, jaw, ribs and pelvis.
-Lesions of the appendicular skeleton are less frequent
and usually involve the metaphyses of bones.
Clinical findings:
- May be asymptomatic, produce palpable mass or
cause pain and even a pathologic fracture.
Imaging:
- Oval or elongate and lucent, with well circumscribed,
sclerotic margins and may expand the bone.
Gross:
- Firm, tan-white and well delineated.
Histopathology:
-Central regions are usually densely cellular and
composed of sheets of small round cells with a
prominent vascular tree that has a
hemangiopericytoma-like pattern.
-Mitotic activity, necrosis, and dystrophic calcification
are common findings.
-This region merges peripherally with a component
composed of intersecting fascicles of plump spindle
cells that have blunt ended nuclei and conspicuous
eosinophilic cytoplasm, which resemble smooth
muscle cells.
Immunohistochemistry:
-Myofibroblastic and more primitive component are
positive for vimentin and smooth muscle
actin, while the myofibroblastic component is more
strongly positive for pan-actin HHF-35.
Prognosis:
-Depends on whether there is one or multiple lesions
and importantly, if there is visceral involvement.
-The prognosis of bone lesions is excellent, and simple
excision is usually curative.
-Patients with multiple visceral lesions, especially those
with involvement of the gastrointestinal tract may have
a fatal outcome from severe hemorrhage.

DESMOPLASTIC FIBROMA
Definition:
-Rare, locally aggresive, solitary tumor microscopically
composed of well differentiated
myofibroblasts with abundand collagen production.
Epidemiology:
-Rare, 0.1% of all primary bone tumors.
-It tends to occur in adolescent and young adults with
near equal gender distribution.
Sites of involvement:
- May involve any bone but is most frequent in
mandible.
Clinical findings:
-Pain and swelling of the affected area are the most
common symptoms.
-Pathologic fracture or deformity of the affected bone can
occasionally be presenting symptom.
Imaging:
-Usually well defined, radiolucent lesion that may expand
host lesion.
-Interlesional trabeculation is frequent.
-Larger lesion often show destruction of overlying cortex
with extension into soft tissue.
-Features of more aggressive growth pattern with
irregular, ill-defined margins and pathological fracture
may be present.
-Honeycombed or moth-eaten patterns have been
described.
-Erosive, destructive pattern may mimic other, more
aggressive lesions.
-DF has low signal intensity in both T1 and T2 weighted
MRI images.
Histopathology:
-Composed of spindle cells (fibroblasts/myofibroblasts)
within an abundant, dense matrix of collagen.
-Degree of cellularity is variable but cellular atypia and
pleomorphism are minimal or absent.
-Mitoses are rare.
-Exhibits an infiltrative destructive growth pattern with
permeation of bone marrow spaces and haversian
canals.
-Borders of the tumor, especially in soft tissue, are
irregular with fingerlike projections infiltrating adipose
tissue and skeletal muscle.
Genetics:
- Trisomies 8 and 20 detected.
Prognosis:
-DF exhibits locally aggressive behavior without capacity
to metastasize.
-Recurrence following curretage and resection are 72%
and 17% respectively.
-Local relapse has been reported as late as eight years
following primary surgery.

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CHEST WALL HAMARTOMA/CHONDROMATOUS HAMARTOMA OF THE CHEST WALL

Definition:
-Known as vascular-cartilaginous hamartoma, vascular
hamartoma of infancy, mesenchymal
hamartoma of chest wall, and chondromatous hamartoma
of the chest wall, is a rare mesenchymal
tumor that usually develops during fetal life or the first
year of infancy.
Epidemiology:
-Fetal life or the first year of life.
-Males are affected slightly more than females.
Sites of involvement:
- Arises from one or multiple ribs.
Clinical findings:
- May be asymptomatic or cause chest wall deformities or
respiratory distress.
Imaging:
-Usually manifest as a large expansile mass that has
well-defined sclerotic margins.
-Tumor erodes the cortex and extends into extrapleural
soft tissues, but is delineated by subperiosteal reactive
bone.
-Intralesional radio densities are often present and may
consist of calcified cartilage that manifest as pop-corn
like speckled foci and mineralized bone that may
produce irregular trabeculations through the mass.
-Hemorrhagic cystic cavities with flui-fluid levels
(secondary aneurysmal bone cyst like regions) are
common, and are seen by CT and T2-weighted MRI.
Gross:
-Frequently large and range in size from 5-16 cm in
diameter.
-Well circumscribed and consist of an admixture of firm,
gray-white, glistening, focally gritty, solid areas, and
numerous blood-filled cystic spaces.
Histopathology:
-Composed of different tissue components including
nodules of hyaline cartilage surrounded by
proliferating fibrovascular tissue, newly deposited bone
and variably sized cysts.
-Cystic spaces, which may dominate the mass, are filled
with blood and the walls are composed of fibrous tissue,
reactive bone and scattered osteoclast type giant cells.
-Hyaline cartilage is moderately to densely cellular with
chondrocytes frequently organized in a pattern that
resembles growth plate.
-At the periphery the matrix frequently undergoes
enchondral ossification.
Prognosis:
-Excellent as recurrence is rare, and likely results from
incomplete resection.
-Main postsurgical complication has been scoliosis

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OSTEOCHONDROMA (EXOSTOSIS)
Definition:
-Cartilage capped bony projection arising on the external
surface of bone containing a marrow
cavity that is continuous with that of the underlying bone.
Epidemiology:
-Most common bone tumor.
- Osteochondroma may be solitary or multiple, the latter
occuring in the setting of hereditary multiple exostoses.
-Solitary lesions account for 80% of cases, and most
affected patients are diagnosed in their second decade of
life
- Male preponderance with a male to female ratio 1.5-2:1.
- Hereditary multiple exostoses (HME) is an autosomal
dominant genetic disorder , and has prevalence of
1 per 50 000 in the general population making it one of
the more common inherited skeletal disease.
-Patients with HME come to medical attention at the
younger age , usually during first decade, because they
cause severe skeletal deformities and are frequently
polyostic.
Sites of involvement:
-Generally arise in bones performed by cartilage.
-Most common site of involvement is the metaphyseal
region of distal femur, uppr humerus, upper tibia and fibula.
Clinical findings:
-Many, if not most lesions, are asymptomatic and found
incidentally. In symptomatic cases, the symptoms are
often related to the size and location of the lesion.
-Most common presentation is that of a hard of long-
standing duration.
Imaging:
-Bulbous lesions on X rays, and they a narrow or broad
(sessile) osseous radiosense stalk, which is attached to
the underlying bone.
-The characteristic feature is a projection of the cortex in
continuity with the underlying bone.
-Excessive cartilage type flocullent calcification should
raise the suspicion of malignant transformation.
-CT scan or MRI images typically show continuity of the
marrow space into the lesion. A thick cartilagenous cap
rises suspicion of malignant transformation.
Gross:
-May be sessile or pedunculated.
-The cortex and medullary cavity extends into the lesion.
-The cartilage cap is usually thin.
-A thick an irregular cap (greater than 2 cm) may be
indicative of malignant transformation.
Histopathology:
-Lesion has three layers - perichondrium (fibrous layer
covering cartilage), cartilage and bone.
-Outer layer is a fibrous perichondrium that is continuous
with the periosteum of the underlying bone.
- Below this is a cartilage cap that is usually less than 2
cm thick (and decreases with age).
-Within the cartilage cap the superficial chondrocytes are
clustered, whereas the ones close to bone resemble
growth plate.
-Loss of the architecture of cartilage, wide fibrous bands,
myxoid change, increased chondrocyte cellularity, mitotic.
activity, significant chondrocyte atypia and necrosis are all
features that may indicate secondary malignant
transformation.
Genetics:
- Abberations involving 8q22-24.1, EXT1 gene.
Prognosis:
-Excision is usually curative.
-Recurrence is seen with incomplete removal.

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CARTILAGE TUMORS
ENCHONDROMA AND ENCHONDROMATOSIS
Definition:
-Benign hyaline cartilage neoplasm of medullary bone.
-Enchondromatosis, is defined as two or more
enchondromas, and occurs in two clinical settings: 90% are
associated with Ollier disease (two or more enchondromas)
10% are seen in Maffuci syndrome (enchondroma +
hemangiomas)
Epidemiology:
-Relatively common, accounting for 10-25% of all benign
bone tumors.
-Age distribution is wide, ranging from 5-80 years.
-Majority of patients present within the second through
fourth decades of life.
-Solitary enchondromas are rare in young children, whereas
multiple enchondromas are encountered more frequently.
-Sexes are equally affected.
Sites of involvement:
-Usually metaphyseal-diaphyseal in location and frequently
affect the short tubular bones of the hands.
-Followed by bones of the feet and the long tubular bones,
especially proximal humerus and proximal and distal femur.
Clinical findings:
-In the small bones of the hands and feet typically present
as palpable swellings, with or without pain.
-Because they often expand these small bones and
attenuate the cortex, they frequently present with
pathological fractures.
-Long bone tumors are more often asymptomatic, and are
detected incidentally in radiographs or bone scans taken for
other reasons.
Imaging:
-Well marginated tumors that vary from radiolucent to
heavily mineralized.
-Mineralization pattern is characteristic, consisting of
punctatae, flocullent, or ring and arc pattern.
-Long bone tumors are usually centrally located within
metaphysis.
-Diaphyseal long bone tumors are less common, and
epiphyseal tumors are rare.
-Enchondromas in the small tubular bones can be centrally
or eccentrically located, and larger tumors may completely
replace medullary cavity.
-More extensive endosteal erosion is considered suspicious
for low grade chondrosarcoma.
-Cortical destruction and soft tissue invasion should never
be seen in enchondromas and would be most consistent
with chondrosarcoma.
Gross:
-Most enchondromas measure less than 3cm and tumor
larger than 5 cm are uncommon.
-They frequently have multinodular architectures, comprised
by nodules of cartilage separated by bone marrow.
-Multinodular pattern appears more common in long bones
compared to confluent growth pattern in small tubular
bones.
Histopathology:
-Nodules of hyaline cartilage that are well demarcated by
the surrounding bone and frequently undrego enchondral
ossification.
-Cartilage shows hypo to moderate cellularity and contains
chondrocytes of variable size.
-Condrocyte nuclei tend to be small, round and
hyperchromatic.
-Scattered binucleated cells may be found.
-Irregular purple granules within the matrix represent
calcifications.
-Chondromas of Ollier disease are histologically similar to
those of sporadic solitary tumors; however, they frequently
demonstrate a greater degree of cellularity, cytologic
atypia, and may contain myxoid stroma, which may be
confused with diagnosis of chondrosarcoma.
Genetics:
- Structural abnormalities involving chromosomes 6
and12 have been detected.
Prognosis:
-Solitary enchondromas successfully treated by intralesional
curretage in most cases, and local recurrences are
uncommon.
-Clinical behavior of Ollier disease is unpredictable and there
is no specialized treatment.
-Most dangerous complication is malignant transformation of
an enchondroma in Ollier disease. This occurs in 25-30%
of affected patients.
-Patients with Ollier disease must have lifetime monitoring of
their tumors.

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CHONDROBLASTOMA
Definition:
-Benign, cartilage producing neoplasm usually arising in the
epiphyses of skeletally immature patients.
Epidemiology:
-Accounts for less than 1% of primary bone tumors.
-Most patients are between 10 and 25 years of age at
diagnosis and there is a male predominance.
-Patients with skull and temporal bone involvement tend to
present at an older age (40-50 years).
Sites of involvement:
-Usually arises in the epiphyses of the distal and proximal
femur, followed by the proximal tibia and proximal
humerus.
-Patients with tumors arising in the flat bones, vertebrae and
short tubular bones tend to be older and skeletally mature,
although rare cases have been reported in children.
Clinical findings:
-Majority of patients complain of localized pain, often mild,
but sometimes of many years duration.
-Soft tissue swelling, joint stiffness and limitation, and limp
are reported less commonly.
-Minority of patients may develop joint effusion, especially
around the knee.
Imaging:
-Typically lytic, centrally or eccentrically placed, relatively
small lesions (3 to 6 cm), occupying less than one half of
the epiphysis.
-Sharpely demarcated, with or without a thin sclerotic
border.
-The presence of sclerotic rim, along with the younger age
of the patient, helps to differentiate chondroblastoma from
giant cell tumor of bone, which generally lacks sclerotic
border and occurs in patients less than 20 years.
-Often helpful, matrix calcifications are only visisble in about
1/3 of patients.
Gross:
- Gritty and grayish white with areas of hemorrhage.
Histopathology:
-Denselly cellular composed of an admixture of
mononuclear chondroblasts and multinucleated osteoclast-
type giant cells.
-Chondroblasts grow in sheets, have eosinophilic
cytoplasm, well defined cell borders, and eccentrically
placed reniform or coffe-bean shaped nuclei.
-Matrix generally consist of poorly formed matrix cartilage,
which mineralization may form 'chicken-wire' pattern
around single cells.
-Mitotic activity and necrosis are commonplace.
-Osteoclast-type giant cells are scattered throughout the
tumor but are most numerous in areas of matrix production
and hemorrhage.
Immunohistochemistry:
-Chondroblasts express S-100 and vimentin but may also
stain for keratin and epithelial membrane antigen.
Genetics:
- Structural anomalies involving chromosomes 5 and 8.
Prognosis:
-80-90% of chondroblastomas are successfully trated by
simple curretage with bone grafting.
-Local recurrence rates range between 14-18% and occur
usually within two years.
-Rare development of pulmonary metastases in
histologically benign chondroblastoma is well documented,
however this metastases are clinically non-progressive and
can often be satisfactorily treated by surgical resection
and/or simple observation.

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LANGERHANS CELL HISTIOCYTOSIS (EOSINOPHILIC GRANULOMA) OF BONE
Definition:
-Previously known as histiocytosis X, is an intraosseous mass of
proliferating Langerhans cells.
-Langerhans cells are dendritic cells that normally populate the
skin, mucosal surfaces, lymph nodes and other tissues where
they function as specialized antigen presenting cells.
- In Lngerhans cell histiocytosis, the proliferating cells are
monoclonal, supporting the theory that the disease is
neoplastic.
Epidemiology:
-LCH is relatively rare disorder, accounting for less than 1% of all
osseous lesions.
-Age distribution is ranging from the first month to 8th decade of
life with 80-85% of cases seen in patients under the age of 30,
and 60% under the age of 10.
-Males are affected twice as often as females.
Sites of involvement:
-Any bone may be involved, although there is predilection for LCH
to involve the bones of the skull, notably the calvarium.
-Other frequently involved sites include the femur, the bones of
the pelvis, and the mandible.
Clinical findings:
-Pain and swelling of the affected area occur most commonly.
-In cases of temporal bone involvement , the presenting features
can show significant clinical overlap with otitis media and
mastoiditis.
-Mandibular involvement , loosening or loss of teeth can be
encontered.
-Vertebral body involvement may result in compression fracture
and possible neurological impairment. LCH is associated with
variety of clinical syndromes.
-Single or multiple lesion restricted to skeleton have been termed
eosinophilic granuloma.
-Multifocal bone disease associated with exophthalmos and
diabetes insipidus is known as Hand-Shuller-Christian disease,
and Letterer-Siwe disease is an aggressive disseminated form
of the disorder that occurs in infants.
-Letterer-Siwe disease usually affects very young childrens less
than 2 y/o, whereas, Hand-Schuller-Christian disease and
eosinophilic granuloma are seen in older children and young
adults.
Imaging:
-LCH lesions are well defined and lytic on radiographs, however,
in a minority of cases may have ill-defined and permeative
margins.
-Cortical involvement may elicit a periosteal reaction.
-Complete resolution of radiographic abnormalities may follow
treatment or occasionally occurs spontaneously.
Gross:
- Involved tissue is soft and is red in color.
Histopathology:
-Proliferating Langerhans cells are ovoid or round histiocyte-like
cells that are arranged in aggregates, sheets, or individually
within a loose fibrous stroma.
-The cells have eosinophilic cytoplasm and contain central ovoid
'coffe bean' shaped nuclei with typical nuclear grooves.
-Chromatin is either diffusely dispersed or condensed along the
nuclear membranes.
-Langerhans cells are frequently admixed with inflammatory cells
including large numbers of eosinophils, as well as lymphocytes,
neutrophils and plasma cells.
-Necrosis may be found in minority cases and if is prominent, is
usually complication of a pathologic fracture.
-Mitotic figures may be seen; however atypical forms are absent.
Immunohistochemistry:
- Langerhans cells are positive for CD1a, S100 and negative
for CD68 and CD45.
Electron Microscopy:
- Intracytoplasmic 'tennis racket' shaped inclusions known as
Birbeck granules.
Prognosis:
-Treatment and prognosis of LCH depends on the site and size of
the lesion, the age of the patient, and the presence or absence
of multifocal disease.
-Monostotic disease is usually managed by curettage, however
tumors located in areas difficult to excise may be treated with
low dose radiation therapy.
-Single or multiagent therapay may be administered in the
setting of disseminated disease.

OTHER LESIONS

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ROSAI-DORFMAN DISEASE
Definition:
- Sinus histiocytosis with massive lymphadenopathy (Rosai-
Dorfman disease) is a rare, proliferative, histiocytic disease
characterized by the enlargement of lymph node sinuses
caused by an aggregation of histiocytic cells that exhibit
marked lymphophagocytosis (numerous phagocytized
lymphocytes are present in cytoplasm).
- Primary or secondary involvement of extranodal sites,
including the skeleton, is frequent.
Epidemiology:
-Majority of patients are teenagers and young adults.
-Mean age 20 years.
-No gender predilection.
-Soliatary RDD in bones was described in young childrens.
Clinical findings:
-Fever and massive cervical lymphadenopathy are the most
frequent symptoms at presentation.
-Other symptoms include weight loss, malaise and night
sweats.
-Quite often the disease fully manifests after a short period of
a nonspecific fever and pharyngitis.
Imaging:
-Skeletal involvement manifests by the presence of solitary or
multifocal defects with poorly or well-demarcated borders.
- RDD lesions are intramedullary and are associated with
cortical erosion, complete cortical disruption, elevation of
the periosteum, or a combination of these features.
-Radiographic manifestations and clinical symptoms suggest
an inflammatory disorder, such as osteomyelitis.
Histopathology:
- In typical cases, the sinuses of lymph nodes are filled with
histiocytic cells.
- These cells have prominent eosinophilic cytoplasm,
indistinct borders, and round or oval nuclei with a very fine
chromatin pattern and a single small nucleolus.
- Nuclear grooves are not present, and some of these cells
may have several nucleoli.
- Occasional cells with multilobulated nuclei may be present.
- Mitotic figures are rare, atypical mitoses are not present.
- The most striking and diagnostically important feature of
histiocytic cells is prominent emperipolesis or
lymphophagocytosis (i.e. the presence of well-preserved
lymphocytes within their cytoplasm).
- In addition to lymphocytes, a smaller number of
phagocytized plasma cells, neutrophils, and red cells is
also present.
- Extranodal disease has all these features except that
histiocytic cells, instead of growing in sinuses, form
irregular
geographic areas separated by other inflammatory cells.
- Involvement of skeletal system has the same features.
Immunohistochemistry:
- Histiocytic cells in RDD are S 100 positive and CD1a
negative.
Prognosis:
-Rosai-Dorfman disease is considered a histologically
benign, proliferative, histiocytic disorder with a variable, but
occasionally fatal, outcome.
-The majority of patients have indolent regressive or clinically
stable disease after several years of follo-up.
-Fatal outcome of the disease is associated with the severe
involvement of extranodal sites (lungs and kidney).

HEMANGIOMA OF BONE
Definition:
-Hemangioma is benign solitary tumor composed of newly
formed vessels of capillary or cavernous type.
Epidemiology:
- Wide age distribution, ranging from the first to eight decades
of life, with nearly 70% of the cases diagnosed in patients
between 30 and 60 years.
- Occasionally hemangiomas become clinically evident during
the first decade of life. There is no s*x predilection.
-They are rare in newborns and infants and reported cases
have arisen in the skull bones.
-The tumors are usually solitary, but multifocal neoplasms
have been described most frequently in the vertebral
columns.
Sites of involvement:
-Hemangiomas frequently occur in craniofacial bones ,
predominantly in calvarium (50%), followed by the
spine (20%).
Clinical findings:
- Relatively common asymptomatic.
Imaging:
-Hemangiomas present as lucent, well demarcated defects.
- In flat bones, they markedly expand the bonecontour and
produce rarefaction with radially oriented striations.
-Vascular nature of the lesion often is suggested by its bubbly
or honeycomb trabeculated appearance.
-Overlying cortex is expanded and thinned, but complete
cortical disruption and invasion into soft tissue are not
present.
-Chracteristic sunburst appearance of hemangioma is seen in
skull lesion (not confuse with that seen in osteosarcoma of
long bones).
-Smaller lesions may present as intracortical rarefaction with
or without a honeycombed appearance and adjacent
sclerosis.
- MRI of hemangiomas generally reveals a low signal on T1-
weighted images and a high signal on T2 weighted images
(fluid content of tumor vessels).
Gross:
-Brown-red or dark red, well demarcated, medullary lesion.
-It may have a honeycomb appearance with sclerotic bone
trabeculae interspersed among hemorrhagic cavities.
Histopathology:
-Hemangiomas are composed of conglomerate of thin-walled
blood vessels.
-Vessels can have dilated open channels (cavernous
hemangioma) or less frequently may be composed of
capillary-sized vessels (capillary hemangioma).
-Majority of bone hemangiomas are of cavernous or mixed
types.
-Vascular channels are lined by a single layer of flat
endothelial cells.
-Intercellular tissue is composed of loose connective tissue
that may show myxoid change.
-Bone may be completely resorbed in affected area.
-Vascular channels of hemangioma are complete, separate
and do not show anastomosing pattern.
Prognosis:
-Asymptomatic small hemangiomas require no treatment;
some may undergo spontaneous regression.
-Symptomatic lesions or those that are large and may cause
pathologic fracture or vertebral collapse require treatment.
-Curretage and bone grafting usually is sufficient.

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PEDIATRIC ORTHOPEDIC PATHLOGY
© Dariusz Borys 2009-2010. All Rights Reserved.
This page was last updated: May 15, 2016
OSTEOID OSTEOMA
Definition:
-Benign bone-forming tumor.
-Similar to osteoblastoma but smaler size (1.5 - 2.0 cm).
Epidemiology:
- Children and adolescent.
Sites of involvement:
- Most common in long bones, femur/tibia (cortex of
metaphysis)
- May be found in any bone.
Clinical findings:
- Intense localized pain particularly at night.
- Pain relieved by aspirin, NSAIDs or surgery.
Imaging:
- Small, round lucency.
- Variable mineralization surrounded by extensive.
sclerosis.
Macroscopy:
- Small cortically based,
- Red, gritty round lesion
Histopathology:
- Limited growth pattern (1.5- 2.0 cm).
- Sharp circumscription near cortical surface (forming nidus).
- Composed of anastomosing bony trabeculae with variable mineralization.
- Bony trabecules lined by plump osteoblast.
- Vascularized connective tissue: surrounded by sclerotic bone.
- Benign giant cells may be present.
Genetics:
- Described loss of 17q.
Prognosis:
- Excellent, recurrences rare after surgical excision.
Differential Diagnosis:
- Osteoblastoma
- Osteomyelitis

GIANT CELL TUMOR
Definition:
-Benign, locally aggressive neoplasm.
-Composed of sheets of neoplastic ovoid mononuclear cells
interspersed with uniformly distributed large, osteoclastlike giant
cells.
Epidemiology:
-Giant cell tumour represents around 4-5% of all primary bone
tumours.
-Peak incidence is between the ages of 20 and 45.
-10-15% of cases occur in the second decade.
-Not commonly seen in adolescents, although cases were described.
-There is slight female predominance described.
Sites of involvement:
-Giant cell tumours typically affect the ends of long bones, especially
the distal femur, proximal tibia, distal radius and proximal humerus.
- About 5% affect flat bones, especially those of the pelvis.
-Multicentric giant cell tumors are very rare and tend to involve the
small bones of the distal extremities.
Clinical findings:
-Patients typically present with pain, swelling and often limitation of
joint movement
-Pathological fracture is seen in 5-10% of patients.
Imaging:
-X-rays of lesions in long bones usually show an expanding and
eccentric area of lysis.
-Lesion normally involves the epiphysis and adjacent metaphysis.
-Extension up to the subchondral plate, sometimes with joint
involvement may be present.
-Rarely, the tumour is confined to the metaphysis,usually in
adolescents where the tumour lies in relation to an open growth
plate,but occasionally also in older adults.
-Diaphyseal lesions are exceptional.
-CT scanning gives a more accurate assessment of cortical thinning
and pe*******on than plain radiographs.
Gross:
- Tissue is usually soft and reddish brown, but there may be yellowish areas corresponding to xanthomatous change.
-Firmer whiter areas represent fibrosis.
- Bloodfilled cystic spaces are sometimes seen and may mimick
aneurismal bone cyst.
Histopathology:
-Tumor is composed of round to oval polygonal or elongated
mononuclear cells evenly mixed with numerous osteoclastlike giant
cells which may be very large and contain 50 to 100 nuclei.
-The nuclei of the stromal cells are very similar to those of the
osteoclasts, having an open chromatin pattern and one or two small
nucleoli.
- The cytoplasm is ill-defined, and there is little intercellular collagen.
- Mitotic figures are invariably present, but no atypical mitoses
present.
- It is now generally accepted that the characteristic large
osteoclastic giant cells are not neoplastic.
- The mononuclear cells, which represent the neoplastic component,
are thought to arise from primitive mesenchymal stromal cells.
- Areas of fibrosis may be present.
- Secondary aneurysmal bone cyst change may occurs in 10% of
cases.
- 1/3 of cases, show presence of intravascular plugs, particularly at
the periphery of the tumour.
- Areas of necrosis are common, especially in large lesions.
- These may be accompanied by focal nuclear atypia which may
suggest malignancy
Genetics:
-Telomeric association is the most frequent chromosomal aberration.
-The telomeres most commonly affected are 11p, 13p, 14p, 15p, 19q,
20q and 21p.
Prognosis:
-Giant cell tumour is capable of locally aggressive behaviour and
occasionally of distant metastasis.
-Histology does not predict the extent of local aggression.
-Local recurrence occurs in approximately 25% of patients, and is
usually seen within 2 years.
-Pulmonary metastases may be seen in 2% of patients with giant
cell tumours, on average 3-4 years after primary diagnosis.

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GIANT CELL TUMOR

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OSTEOMYELITIS
Definition:
Inflammation of bone and marrow also known as infection of bone
May manifest as a primary solitary focus of disease or as a complication of other systemic disease.
May be caused by different bacterial organisms
Types of osteomyelitis:
Pyogenic Osteomyelitis
Hematogenous osteomyelitis commonly occurs in children.
Staphylococcus aureus is the most common organism responsible for pyogenic osteomyelitis
H. inflenzae & group B streptococci are frequent pathogens in neonatal infection.
Gram negative organisms are isolated from patients with genitourinary infection or who are IV drug abusers
Almost always caused by bacteria.
Organisms reach to the bone by:
1 hematogenous spread
2 extension from a contiguous site
3 direct implantation
The latter (3) occurs as a complication of a compound fracture or of surgery.
Symptoms:
High fever, localized pain and swelling
Labs:
high white cell count, high ESR.
Most frequent site in children:
distal femur, proximal tibia
proximal humers and distal radius all of which are areas of rapid growth
Site of infection in the bone is influenced by high vascular supply
In neonate, the metaphyseal vessels pe*****te the growth plate resulting in infection of metaphysis, epiphysis or both
In children metaphyseal localization.
In adult subchondral region or vertebral localization
Morphology:
Rupture of the periosteum leads to soft tissue abscess and draining sinus
In infants epiphyseal infection spread through the articular surface causing destruction of the cartilage leading to joint infection also known as septic or suppurative arthritis.
In vertebrae, the infection destrys the hyaline cartilage end plate and intervertebral disk and spreads to the adjacent vertebrae
Depends on stage (acute, subacute or chronic).
Bacteria localized in bone induce acute inflammation and cell death.
Bone necrosis in 48 hours and spread of infection to the periosteum via haversian system leading to periosteal elevation and subperiosteal abscess formation.
This process impairs the blood supply causing segmental bone necrosis, the dead piece of bone is known as Sequestrum.
Radiology:
Lytic focus of bone destruction with peripheral zone of sclerosis and reactive periosteum.
Hot spots on bone scan.
MRI: increased signal intensity in the medullary space.
D.D.: small round blue cell tumor
Chronic osteomyelitis:
One week after the infection, host response evolves with infiltration by chronic inflammatory cells and release of cytokines which in turn stimulates osteoclastic bone resorption, ingrowth of fibrous tissue and reactive new bone formation.
Reactive bone in the form of a living tissue around the segment of necrotic bone (sequestrum) is known as involucrum.
Variants of osteomyelitis:
Brodie abscess – small intraosseous abscess that frequently involves the cortex and is walled of by reactive bone. It may mimick tumor.
Sclerosing osteomyelitis of Garre affects the jaw bone with extensive new bone formation.
Chronic Recurrent Multifocal Osteomyelitis
Clinical course:
Blood culture may be positive
Antibiotics and surgical drainage are the usual treatment.
In 5% to 25% cases, the infection persists as chronic osteomyelitis.
Acute flare ups can occur after years of dormancy.
Rare complications: fracture, sepsis, scc in the sinus and bone sarcoma.

Angiomatoid Fibrous Histiocytoma of Bone
Definition:
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