A case of intracardiac RREB1::MKL2 spindle cell mesenchymal tumor.

This case describes a 57-year old female patient with no past medical history who was referred for investigation of dyspnea. Cardiac exams revealed a voluminous septate mass with liquid tone, developed from the right atrium with minimal compression of the inferior vena cava. Patient underwent surgical removal of the mass with reconstruction of interatrial septum using pericardial patch. Histopathological examination of the mass revealed RREB1::MKL2 fusion characteristic of ectomesenchymal chondromyxoid tumors of the tongue. This is the first description of cardiac localization of RREB1::MKL2-fusion positive mesenchymal tumor.