Kaposiform hemangioendothelioma: the first reported case in a nonhuman animal species.

Kaposiform hemangioendothelioma is a rare vascular tumor that almost exclusively occurs in children. It is a low-grade malignant neoplasm that is locally aggressive but without proven metastatic potential. Herein, we describe a case of Kaposiform hemangioendothelioma in a 10-year-old male dog. To the best of our knowledge, this is the first report of this vascular tumor occurring in a nonhuman animal species. The tumor was located on the ventromedial surface of the posterior limb. Microscopic examination of the lesion revealed a multinodular tumor with sheets of spindled endothelial cells forming vascular slits similar to Kaposi's sarcoma and peripheral tumor lobules resembling capillary hemangioma.