Immunocytochemical diagnosis of skin tumours of the dog with special reference to undifferentiated types.

Immunoperoxidase techniques for S-100 protein, keratin, cytokeratin, vimentin and desmin were applied to 65 canine skin tumours. These included eight squamous cell carcinomas, eight fibrosarcomas, eight melanomas, eight mastocytomas, eight haemangiosarcomas, eight leiomyosarcomas, five liposarcomas and 12 poorly differentiated tumours. Consistent results were obtained within each group. Cytokeratin and keratin immunoreactivity was detected only in squamous cell carcinomas. Vimentin was present in fibrosarcomas, melanomas, haemangiosarcomas, mastocytomas, leiomyosarcomas and liposarcomas. S-100 protein immunoreactivity was detected in melanomas, haemangiosarcomas, liposarcomas and leiomyosarcomas. Only leiomyosarcomas were positive for desmin. According to these results the 12 anaplastic tumours were diagnosed either as carcinomas, fibrosarcomas or malignant melanomas.