General Considerations

•thymic LSA is the most common thymic tumor in dogs

•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 Presentation

•mean age 5.8 years

•breed predisposition: none

•neurologic signs due to direct infiltration into thoracolumbar spinal cord

•polyostotic bone involvement reported in puppy with thymic LSA

•canine thymic LSA is frequently associated with hypercalcemia (25%-50%) and generalized lymphadenopathy

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

•lymphoblastic LSA is the most common form accounting for 75% (8/12) cases

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