Evaluation of cell proliferation markers in canine cutaneous histiocytoma and transmissible venereal tumour

Two neoplastic conditions of dog namely cutaneous histiocytoma, a benign but rapidly growing tumour and transmissible venereal sarcoma, a metastasizing malignant tumour, presented almost similar microscopical pictures, thereby posing great difficulty in their differential diagnosis. Three different cell proliferation markers viz. mitotic indices, argyrophil nucleolar organizer region (AgNOR) counts and proliferating cell nuclear antigen (PCNA) indices were applied in an attempt to differentiate these canine neoplasms. Contrary to expectations, our results revealed less proliferative activity in tumour cells of venereal sarcoma as shown by lower indices [mitoses (5.32), AgNORs (12.01) and PCNA (205.82)] compared to the cutaneous histiocytoma cells (11.34,13.90 and292.40)]. The results on limited number of tumour cases suggested the higher aggressiveness of growth of canine cutaneous histiocytoma in comparison to venereal sarcoma.