Clinical features and outcomes of Merkel cell carcinoma in 20 cats

• Published in: Veterinary & comparative oncology Vol. 16; no. 4; pp. 554 - 561
• Main Authors: Sumi, A., Chambers, J. K., Doi, M., Kudo, T., Omachi, T., Uchida, K.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.12.2018
• Subjects: cat; clinical outcome; immunohistochemistry; Merkel cell carcinoma; pathology; pathology; immunohistochemistry; Merkel cell carcinoma; clinical outcome; cat
• ISSN: 1476-5810; 1476-5829
• DOI: 10.1111/vco.12414

The biological behaviour and prognostic factors of Merkel cell carcinoma (MCC) in 20 cats were studied. The tumours were surgically removed and histopathologically examined. The animals were 8 to 20 years old (median age: 14 years), and the tumours were predominantly located in the neck and head. Follow‐up data were available in 17 cases, and 12 cats died within a year of surgery. The overall median survival time after resection was 243 days (range 16‐360 days). Recurrence occurred in 11 cases, although 6 of them (55%) were found to be margin‐negative. Possible metastasis occurred after the surgery in 10 cases, although 6 of them (60%) were found to be margin‐negative. The histopathological features of MCC included tumour necrosis in 16 cases (80%), vascular invasion in 6 cases (38%) and high mitotic counts (median: 28.5 per high‐power field). Irregular acanthosis was noted adjacent to the tumours in 9 cases (60%). Immunohistochemically, the tumour cells were positive for cytokeratin (CK) 20 and p63 in all cases, synaptophysin in 19 (95%) cases, and CK18 in 16 cases (80%). The study shows that feline MCC is associated with a poor prognosis and exhibited a strong tendency towards local recurrence, regional lymph node metastasis and distant spread.