ABSTRACT
Acute lymphoblastic leukemia [ALL] is the most common malignancy diagnosed in children. Extramedullary leukemia including hepatosplenomegaly, lymphadenopathy, and mediastinal mass are the clinical presentations of T-cell ALL. Pericardial effusion and atrial mass are rare presentations of pediatric leukemia. We report a 15-year-old girl with T-cell ALL, who presented initially with pericardial effusion and cardiac tamponade and subsequently developed right atrial mass. The mediastinal and right atrial masses were excised by surgical procedure as a treatment strategy for prevention of arrhythmia and sudden death. T-cell ALL can present with pericardial and mediastinal involvement as an initial manifestation. Pericardiocenthesis and systemic anticancer chemotherapy without local chemotherapy should be considered in these cases