17/12/2025
🔬 𝐂𝐘𝐓𝐎𝐈𝐍𝐒𝐈𝐆𝐇𝐓𝐒: 𝐕𝐢𝐫𝐚𝐥 𝐩𝐚𝐩𝐢𝐥𝐥𝐨𝐦𝐚 🧬
𝑩𝒚 𝑴𝒂𝒓𝒊𝒐 𝑪𝒂𝒃𝒆𝒛𝒂𝒔-𝑪𝒂𝒍𝒗𝒐 𝑫𝑽𝑴, 𝑪𝑺𝑨𝑽𝑷
𝘐𝘯𝘵𝘳𝘰𝘥𝘶𝘤𝘪𝘯𝘨 𝘊𝘺𝘵𝘰𝘐𝘯𝘴𝘪𝘨𝘩𝘵𝘴 — 𝘢 𝘯𝘦𝘸 𝘴𝘦𝘨𝘮𝘦𝘯𝘵 𝘸𝘩𝘦𝘳𝘦 𝘰𝘶𝘳 𝘱𝘢𝘵𝘩𝘰𝘭𝘰𝘨𝘪𝘴𝘵𝘴 𝘥𝘪𝘴𝘤𝘶𝘴𝘴 𝘴𝘦𝘭𝘦𝘤𝘵𝘦𝘥 𝘤𝘢𝘴𝘦𝘴 𝘢𝘯𝘥 𝘵𝘩𝘦 𝘥𝘪𝘢𝘨𝘯𝘰𝘴𝘵𝘪𝘤 𝘪𝘯𝘴𝘪𝘨𝘩𝘵𝘴 𝘣𝘦𝘩𝘪𝘯𝘥 𝘵𝘩𝘦𝘮. 📚
A five-years old female Cocker Spaniel arrived at the clinic with a rapidly growing cutaneous mass in the inguinal area. On examination, the lesion appeared as a small raised nodule. The main clinical suspicion at the time was a round cell tumour, such as a histiocytoma or mast cell tumour.
A fine-needle aspirate was submitted for cytology. The sample revealed high numbers of keratinised epithelial cells.
They had round to oval nucleus, condensed to clumped chromatin, and large amount of angular cytoplasm. Many cells contained small clear cytoplasmic vacuoles and a fine eosinophilic hue. Only mild anisocytosis and anisokaryosis were noted. These features are consistent with a papilloma.
Papillomas are common in dogs and typically present as sessile or pedunculated growths with a wart-like appearance. They can arise from viral or non-viral causes. Cytologically, they are characterised by polygonal squamous epithelium with benign appearance. The presence of squamous cells with eosinophilic cytoplasm and small clear vacuoles, known as koilocytes, is a common finding in viral papilloma; although, they are not pathognomonic. Viral papillomas often regress spontaneously within a few months, while non-viral papillomas are not expected to regress. In all cases, cytology plays a key role helping guide clinical decision-making.
By Mario Cabezas-Calvo DVM, CSAVP
