+ 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