Prognostication of Canine Mammary Carcinomas Based on Histological and Immunohistochemical Subtypes

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Stevens, Brian
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University of Guelph

Mammary tumours are the most common tumour in intact female dogs. Although the majority are benign, it can be difficult to determine which histologically malignant mammary tumours will actually metastasize or recur. To address this, I investigated several potential prognostic markers for canine mammary carcinomas in combination with histological and immunohistochemical subtypes. The presence of neoplastic cell emboli and overt metastasis, and invasion of neoplastic cells at the periphery of the tumour were the best prognostic markers for predicting poor survival. Of the most common histological subtypes, solid carcinomas were associated with the worst prognosis followed by ductal carcinomas and finally, complex carcinomas. With regards to immunohistochemical subtypes, ER&HER negative (similar to triple negative breast cancer in humans) and unclassified carcinomas had shorter survival and were associated with poor prognostic indicators when compared to luminal A carcinomas. Regardless of other factors, estrogen receptor (ER) negative carcinomas were associated with shorter survival than ER positive carcinomas. In summary, this study demonstrated that canine mammary carcinomas exhibited similar immunohistochemical subtypes to those in human breast carcinoma with similar patterns of prognosis between these subtypes. As well, we show that specific markers that can be used to better prognosticate canine mammary carcinomas, including specific histological subtypes and ER status.

canine, mammary, carcinoma, immunohistochemical subtypes, histological subtypes, grading, prognosis, estrogen receptor, tissue microarray