Left Atrial High-grade Sarcoma With Focal Osteosarcomatous Differentiation.

Approximately 75% of cardiac tumors are benign, and 25% are malignant cardiac tumors. Of these, sarcomas are extremely rare and have been described in isolated case reports. Due to its rarity, there is no published guideline for the management of this pathological entity. We present a case of an 85-year-old female who presented to our hospital with a chief complaint of shortness of breath and pinpointed left-sided chest pain. Computed tomography of the chest showed a filling defect in the left atrium concerning a mass versus thrombus. A transesophageal echocardiogram showed a 4 cm multi-lobular echogenic mass with calcifications in the left atrium likely arising from the pulmonary vein suspicious for malignancy. Cardiovascular surgery department scheduled the patient for surgical debulking/removal via a minimally invasive approach. The specimen was reported to be multi-lobular and was resected in several fragments of tan, fleshy, and somewhat gelatinous appearing tissue in aggregate. Histopathology showed spindle cell malignant neoplasm with small foci of bone and cartilaginous formation, suggestive of osteosarcoma. Expert consultation at John Hopkins reported this to be a high-grade sarcoma with focal osteosarcomatous differentiation. Cardiac synovial sarcomas are less than 0.1% of all primary cardiac tumors reported in the literature. Cardiac synovial sarcomas are not extensively described in literature due to their low incidence and prevalence. Thus, it is important to report cases and follow outcomes. This case reports an extremely rare diagnosis that has been reported in less than seven case reports.