General Considerations

•thymic LSA is the most common thymic tumor in cats

•thymic LSA is less circumscribed than thymoma with local extension through the thoracic inlet, around the heart base or into the lungs, pericardium, or intercostal or cervical musculature

Clinical Features

•mean age 4.1 years

•breed predisposition: Siamese

•FeLV reported in 50%-80% of thymic LSA

•histopathologic features: neoplastic lymphocytes ranging from well-differentiated small lymphocytes to lymphoblastic and histiocytic forms

•lymphoblastic LSA is the most common for accounting for 58% (11/19) cases

•mediastinal LSA invading cranial vena cava (with thrombosis and cranial vena cava syndrome) has been reported

Diagnosis

•thoracocentesis or FNA: lymphoblasts rather than mature lymphocytes seen with thymoma

•ultrasonography: homogenous and hypoechoic compared to mixed echogenicity with thymoma

Treatment

•chemotherapy

•± radiation therapy