Invasive leiomyosarcoma involving the tongue of an Arabian mare.

The research article discusses the case of a 10-year-old Arabian mare diagnosed with Leiomyosarcoma, a rare type of muscle cell cancer, found in her tongue. The diagnosis was made using physical examination, blood tests, computed tomography (CT), and cellular analysis of the mass.

Background and Diagnosis

• The mare was experiencing excessive salivation, difficulty swallowing, severe bad breath, and trouble chewing for four months. An examination revealed a firm, multilobulated mass on the left ventral face of the tongue.
• The following diagnostic tests were conducted: physical and oral examination, complete blood count and serum biochemistry profile, computed tomography evaluation of the head, and histopathology (study of disease tissues) of the mass.

Findings

• The CT head scan showed a homogeneous mass in the mouth, confirming the depth of invasion of the growth on the tongue. It also revealed a small mineral buildup at the left dorsal mandibular border and increased density of the submandibular lymph nodes, suggesting possible cancer spread.
• Upon necropsy (animal post-mortem), the tongue showed a large, irregular, nodular, and partially ulcerated mass in the body’s ventral aspect.

Pathology

• The histology of the tongue indicated a cancerous growth originating from mesenchymal muscle- the loose, connective tissue from which smooth muscle arises. There were distinctive cells and structures visible in some parts of the specimen.
• An immunohistochemistry panel showed a positive reaction for Calponin and Desmin, proteins present in smooth muscle cells. These findings confirmed the diagnosis of soft tissue leiomyosarcoma in the tongue.
• Together, the immunohistochemistry results and the cell and structure appearances suggested Leiomyosarcoma originated from the tissue surrounding the blood vessels (perivascular wall tissue).

Significance

• Tumors of this type are rare in veterinary medicine. To the authors’ knowledge, this is the first report of oral leiomyosarcoma in a horse, using histopathology, immunohistochemistry and imaging techniques for diagnosis.