A Rare Case of a Primary Unilateral Low-Grade Paratesticular Leiomyosarcoma in a 2 Years Old Dog

First report of primary testicular leiomyosarcoma in two dogs

BACKGROUND

Testicular tumours are common in dogs and, among them, interstitial cell tumours, seminomas and sustentacular cell tumours are the most reported. Mesenchymal testicular tumours are rarely reported in humans as in veterinary medicine where only three cases of sarcomas (leiomyomas and leomyosarcomas) have been described in two stallions and in a ram.

CASE PRESENTATION

The present cases regarded a 12-year-old mixed-breed dog and a 10-year-old American Staffordshire Terrier that underwent bilateral orchiectomy. Formalin fixed testes were referred for histopathological diagnosis. At gross examination, in one of the testes of both dogs, a white, firm and variably cystic testicular mass, effacing and replacing the testicular parenchyma was detected. Samples were collected from both neoplastic and contralateral testes, routinely processed for histology and serial sections were also examined immunohistochemically with primary antibodies against cytokeratins, vimentin, Von Willebrand factor, inhibin-α, α-smooth muscle actin, smooth muscle myosin and desmin. Histopathological features as well as the immunohistochemical results, positive for vimentin, actin, myosin and desmin, confirmed the mesenchymal origin and the myoid phenotype of both testicular tumours supporting the diagnoses of leiomyosarcoma.

CONCLUSIONS

To the authors knowledge these are the first cases of primary testicular sarcoma reported in the canine species. However, even rare, these tumours deserve to be considered in routine diagnosis when a testicular spindle cell tumour is observed. The immunohistochemical panel applied was useful to distinguish the present tumours from undifferentiated Sertoli cell tumours confirming the diagnosis of leiomyosarcoma.

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.