Canine transmissible venereal tumour: A morphological and immunohistochemical study of 11 tumours in growth phase and during regression after chemotherapy

Eleven dogs with canine transmissible venereal tumour (CTVT) were given vin cristine sulphate chemotherapy to induce tumour regression. Biopsy specimen s were collected from tumours during the growth phase, before chemotherapy, and again from the same dogs during the regression induced by chemotherapy . Laboratory assessment included cytology, histology, the number of tumour cells in relation to the number of intratumoral leucocytes proliferative an d apoptotic fractions of tumour cells, intratumoral vessel density, and fib rosis. The results revealed that during regression, tumour cell proliferati on ceased, apoptosis increased, leucocytes increased (with increased propor tion of T lymphocytes), tumour parenchyma collapsed around intratumoral ves sels, and fibrosis increased. These results, which were similar to findings in dogs with spontaneous regression of CTVT, suggest that tumour immunity plays a role in tumour regression after modest chemotherapy. (C) 2000 Harcourt Publishers Ltd.