Canine Invasive Lobular Carcinoma of the Mammary Gland: Morphological and Immunohistochemical Characterizations of Three Cases

SummaryInvasive lobular carcinoma (ILC) represents 15% of invasive human breast tumours. This report describes the morphological and immunohistochemical features of three canine mammary tumours comparable with human ILC. These tumours were composed of a non-delimited proliferation of discrete cells infiltrating fibrous connective tissue. Multifocal in-situ carcinoma associated with invasive lesions was present. Invasive tumour cells and in-situ lesions expressed cytokeratin and CK34betaE12, but not E-cadherin. Based on these morphological and immunohistochemical characteristics, the tumours were classified as canine ILC.