Pleomorphic lobular carcinoma in a cat: Clinical, histopathological, and immunohistochemical characterization

Mammary carcinomas in cats are highly aggressive neoplasms, often with the development of metastasis. Pleomorphic lobular carcinoma, on the other hand, is an invasive carcinoma with aggressive behavior, rarely diagnosed in humans and dogs. This report describes a case of pleomorphic lobular carcinoma in cats. The histopathological and immunohistochemical features of the neoplasm in this species were characterized. The neoplasm was diagnosed in a 10-year-old cat, with regional lymph node involvement at the time of diagnosis, but without systemic signs based on imaging tests performed prior to mastectomy. However, respiratory clinical signs developed approximately 40 days after surgery, accompanied by neoplastic pleural effusion, and the patient was euthanized due to the onset of neurological signs and poor prognosis. Although uncommon, pleomorphic lobular carcinoma is a neoplasm that can affect cats, and given its poor prognosis, it is important for oncologists and pathologists to be familiar with this entity.