Diagnostic exercise: epithelioid hemangiosarcoma mimicking metastatic prostatic neoplasia in a dog.

A 10-year-old intact male Labrador Retriever dog was euthanized because of rapid deterioration after suffering from mild chronic cough, hematuria, acute blindness, ataxia, and lethargy. Clinical examination revealed blepharospasm and hyphema, with clear discharge from the right eye; a firm mass in an enlarged right testicle; a mass in the irregularly enlarged prostate; and nodules in the left kidney, liver, and spleen detected by abdominal sonography. Cytologic evaluation of fine needle aspirates from the prostate, testis, and kidney comprised large, clustered or individualized, anaplastic cells that lacked convincing tissue differentiation. Necropsy examination revealed an irregularly enlarged prostate with dark tan to red zones and multiple, discrete, beige to dark red nodules that ranged from 0.5 to 6 cm in diameter in the lung, liver, left kidney, right testis, colon wall, stomach wall, and brain. On histologic examination, discrete nests of anaplastic carcinoma-like tumor cells were found in sections of all affected organs. Results of immunohistochemical examination revealed widespread expression of von Willebrand factor and the absence of cytokeratin in neoplastic cells. The diagnosis was metastatic epithelioid hemangiosarcoma, primary site unknown.