Canine and feline in situ mammary carcinoma: A comparative review.

Carcinoma in situ of the breast is a well-known entity in humans. In veterinary medicine, particularly in canine and feline mammary literature, there is no agreement whether the term in situ should be used to indicate a specific carcinoma histotype or the noninvasive status of a carcinoma of any histotype. Moreover, in the most recent histologic classification of mammary tumors published by the Davis-Thompson Foundation, it is suggested to abandon the term carcinoma in situ given the lack of standardized criteria defining this entity, replacing it with epitheliosis or ductal/lobular hyperplasia with severe atypia. This publication presents a critical review of the term in situ in human and veterinary medicine considering the evolution of the term over the years and its heterogeneous use by different authors, including variations in immunohistochemical markers for classification. This review aims to point out the lack of uniformity in the nomenclature and classification issues in veterinary medicine regarding the use of the term in situ, laying the ground for a process of standardization in future publications.

Canine invasive lobular carcinoma of the mammary gland: morphological and immunohistochemical characterizations of three cases.

Invasive 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.

Immunohistochemical localisation of cytokeratin and vimentin intermediate filament proteins in canine mammary tumours.

Monoclonal antibodies to human stratifying keratin (StK), simple keratin (SK), broad spectrum keratin (BSK) and vimentin were applied to 47 canine mammary tumours (three benign hyperplasia, 26 benign mammary tumours, one malignant mixed tumour, two malignant complex tumours, seven lobular carcinomas, three papillary carcinomas and five squamous cell carcinomas). In benign hyperplasia the SK antibody reacted with acinar and duct epithelial cells; the StK and BSK antibodies reacted strongly with duct epithelial cells in the canine mammary tumours expressed mainly keratins of stratified epithelia rather than those of simple epithelia. Myoepithelial cells in complex and mixed tumours can express StK and vimentin. The finding might be helpful in the assessment of complex tumours where stromal reactions may be confused with myoepithelial neoplastic proliferation. Stromal mesenchymal tissues, including precartilage in complex tumours, and clearly differentiated myoepithelial cells always stained positively for vimentin. Occasional carcinoma cells stained positively for vimentin.