Invasive leiomyosarcoma involving the tongue of an Arabian mare

A 10 year-old endurance Arabian mare was presented with an invasive, firm, multilobulated mass at the left ventral face of the tongue. The mare had a history of four months of ptyalism, dysphagia, severe halitosis, and dysmastication. The Evaluation of the horse included physical and oral examination, complete blood count and serum biochemistry profile, computed tomography evaluation of the head, and histopathology of the mass. The computerized tomography (CT) head scan showed the homogeneous mass in the oral cavity confirming the degree of invasion on the tongue, as well as a small mineral focus at the left dorsal mandibular border and increased density of the submandibular lymph nodes. At necropsy, gross findings in the oral cavity revealed an irregular, nodular and partially ulcerated mass at the level of the body of the tongue in the ventral aspect, with a size of approximately 10 × 15 × 8 cm. Histologically, the tongue revealed a neoplastic process of mesenchymal muscle origin. The tumor cells showed distinctive morphological and architectural patterns in some areas. An immunohistochemistry panel was done yielding a positive reaction for Calponin and Desmin, confirming diagnostics of as a soft tissue leiomyosarcoma in the tongue. Immunohistochemistry results, in combination with histopathologic morphology, were suggestive of a leiomyosarcoma originating in the perivascular wall tissue. Oral leiomyosarcoma are very rare in veterinary medicine, and to the authors' knowledge, this is the first case report to utilize histopathology, immunohistochemistry and imaginology to describe oral leiomyosarcoma in a horse.