A Challenging Case of Pediatric Cardiac Leiomyosarcoma: Surgery, Recurrence, and Remission With Tyrosine Kinase Inhibitor.

Primary cardiac leiomyosarcoma is exceedingly rare in children. We describe a four-year-old girl presenting with recurrent syncope due to a mass in the right ventricular outflow tract causing severe obstruction. She underwent surgical resection of the tumor, presumed as benign on cardiac imaging. The histopathology, however, confirmed it to be leiomyosarcoma. Post-surgery there was rapid tumor regrowth despite first-line chemotherapy, which prompted treatment with pazopanib, a multitargeted tyrosine kinase inhibitor, which led to complete remission within six months, obviating the need for a high-risk reoperation. This case highlights the utility of pazopanib in pediatric sarcomas unresponsive to conventional therapy.