Cytological study on the anterior pituitary of senile untreated beagle bitches with spontaneous mammary tumours.

Pituitaries were obtained from senile untreated Beagle bitches of comparable age (7-9 years) and genital status. The animals were divided into three groups; one was normal (without mammary lesions), one had benign tumours and one had mammary adenocarcinomas. PRL-, STH-, ACTH- and gonadotrophin-producing cells are studied and counted in serial paraffin sections stained with histochemical techniques. The animals with mammary malignancy displayed a marked increase in the relative number of PRL and ACTH cells with morphological signs of higher secretory activity in most cells, compared with that in normal bitches or bitches with benign tumours. STH cells in bitches with adenocarcinomas were reduced in number; however the secretory activity in these animals was the same as that observed in the normal bitches. In the animals with benign mammary tumours, STH cells showed morphological indication of higher secretory activity than in the other groups. PRL and ACTH cells were slightly increased in number and had slightly higher activity than that in normal bitches. These findings may suggest a role for hypophyseal hormones in mammary neoplasias.