Primary Verocay Body-rich Epididymal Leiomyosarcoma in a Dog.

Leiomyosarcomas arising from paratesticular structures are rare. We report a case of epididymal sarcoma in an aged male Rottweiler that had histological features suggestive of neural origin but with muscular histogenesis confirmed by immunohistochemistry. Histologically, the lesion comprised a hypercellular neoplasm that had interlacing bundles of spindloid cells, prominent nuclear palisading and many Verocay bodies. Immunohistochemically, the neoplastic cells were strongly positive for smooth muscle markers but negative for neural markers, leading to the diagnosis of leiomyosarcoma. While the presence of nuclear palisading and Verocay bodies has been regarded as strong evidence for the diagnosis of schwannomas, the present report documents the presence of true Verocay bodies in a non-neuronal tumour. It also indicates that immunophenotyping is required for an accurate diagnosis when Verocay bodies are detected in sarcomatous or spindle cell tumours and provides prognostic information on this case. To the best of our knowledge, this is the first report of the presence of true Verocay bodies in a neoplasm other than a nerve sheath tumour in animals.