Canine mammary gland tumours; a histological continuum from benign to malignant; clinical and histopathological evidence^*

TLDR

The study investigates clinical and histopathological evidence of progression from benign to malignant mammary tumors in dogs, drawing parallels to human breast cancer epidemiology. Data were collected from 90 female dogs comprising 236 mammary tumors, with clinical and histopathological assessments performed. Malignant tumors were associated with older age, larger size, higher likelihood of multiple lesions and new primary tumors, supporting a histological continuum from benign to malignant tumors analogous to human breast cancer.

Abstract

This study describes the clinical and histopathological findings in dogs with mammary gland tumours, and compares the histopathological and clinical evidence consistent with progression from benign to malignant to human breast cancer epidemiology. Clinical and histopathological data on 90 female dogs with 236 tumours was included. Dogs with malignant tumours were significantly older than dogs with benign tumours (9.5 versus 8.5 years), P = 0.009. Malignant tumours were significantly larger than benign tumours (4.7 versus 2.1 cm), P = 0.0002. Sixty-six percent had more than one tumour, and evidence of histological progression was noted with increasing tumour size. Dogs with malignant tumours were significantly more likely to develop new primary tumours than dogs with benign tumours, P = 0.015. These findings suggest that canine mammary tumours progress from benign to malignant; malignant tumours may be the end stage of a histological continuum with clinical and histopathological similarities to human breast carcinogenesis.