A Metastatic Lipid-Rich Carcinoma of the Mammary Gland in a Female Cat: Clinicopathological, Histopathological and Immunohistochemical Features

Abstract

Lipid-rich invasive human breast cancer is a rare enigmatic entity among special types of infiltrating duct carcinoma. Our paper reports a lipid-rich mammary carcinoma in a female cat with the gross, microscopic and immunohistochemical description of the tumor. A 13-year-old intact adult female, mixed-breed cat was presented by the owner to the Laboratory of Pathologic Anatomy from the Faculty of Veterinary Medicine Cluj-Napoca, Romania. A complete necropsy examination was performed in our laboratory. The tissue samples were collected and processed by paraffin technique for further histological, histochemical, immunofluorescence and immunohistochemical examination. During the necropsy examination, a subcutaneous mass was discovered on the chest. Several variably sized, well-demarcated neoplasms were noted in the right axillary lymph node, right thoracic wall, pleura, lungs, liver, spleen and kidney. Histologically, the cells frequently formed tubuloacinar structures. The morphology of the described tumor showed features of a poorly differentiated mammary carcinoma. Numerous tumoral cells were large and polygonal, with abundant cytoplasm that showed foam-like cytoplasm. The tumoral cells contained either multiple small or large and solitary vacuoles that pushed the nucleus to the periphery of the cell. Intracytoplasmic vacuoles of the neoplastic cells were positive for Oil-Red-O and negatively with Periodic Acid–Schiff. As for immunofluorescence/immunohistochemistry, nonvacuolated and vacuolated neoplastic cells were positive for cytokeratin and negative for vimentin. Histochemical and immunohistochemical analysis support a diagnosis of lipid-rich mammary carcinoma. This is the second reliable record of a lipid-rich mammary carcinoma in female cat and the first one with internal metastases.