RESUMO
This article presents a unique case of primary myxofibrosarcoma, an exceptionally rare cardiac neoplasm, in a 16-year-old girl. With fewer than 40 documented cases, this tumor's occurrence in adolescence is particularly uncommon. The patient presented with right-sided paresthesia and subsequent right hemiparesis and dysarthria, along with bilateral pleural effusion. Imaging tests revealed a cerebral ischemic lesion and the presence of a left atrial mass. Initially suspected as a myxoma, the tumor exhibited significant infiltration. Despite prompt excision and cardiac intervention, the patient experienced rapid decompensation and succumbed to heart failure 2 days later. Histopathological analysis revealed an intermediate grade myxofibrosarcoma. This case underscores the diagnostic complexity, emphasizing the need for early identification given the grim prognosis associated with cardiac myxofibrosarcomas, requiring detailed imaging, surgical, and histopathological insights.