Primary Ovarian Rhabdomyosarcoma in a Dog

SummaryA 10-year-old female English pointer was diagnosed with an ovarian tumour with abdominal metastases. Ultrasonography revealed several nodules of 1–5 cm diameter within the abdominal cavity. Fine needle aspiration cytology of the nodules suggested a malignant mesenchymal tumour. On necropsy examination the right ovary and its capsule were enlarged and there were white–red, friable nodular masses distributed over the surface of the pancreas, liver, omentum, mesentery and serosae of the small and large intestines. Microscopical evaluation revealed neoplastic cells with a high degree of pleomorphism and vascular invasion. Immunohistochemically, the neoplastic cells expressed myosin, desmin, vimentin and CD10, but were negative for cytokeratin, placental alkaline phosphatase, inhibin-alpha and smooth muscle actin. Based on these findings a diagnosis of primary ovarian alveolar rhabdomyosarcoma was made.