Malignant luteoma in a sow.

A case of malignant luteoma was found in a 3-year-old Landrace sow. A large neoplastic mass was present in the left ovary and small neoplastic nodules were seen in the right ovary. There were metastatic lesions in the diaphragmatic peritoneum and heart. The neoplastic cells were extremely pleomorphic and among them relatively large cells predominated. The neoplastic cells had lipid droplets, membranous structures, intermediate filaments and lipofuscin granules in their cytoplasm.