Right Atrial Blood Cyst Incidentally Detected by Computed Tomography for Metastatic Breast Cancer in an Adult Female Patient: A Case Report

Cardiac blood cysts are benign congenital cardiovascular tumors that are rare in adults. A 70-year-old woman who underwent left mastectomy for left breast cancer 9 years ago was referred to our institution for a right atrial mass that measured 35 × 30 mm and was detected incidentally by computed tomography for metastatic breast cancer and transthoracic echocardiography. The mass was attached to the interatrial septum by a stalk. Although it was asymptomatic, surgical resection was performed because of the risk of pulmonary embolism. The mass contained blood, and histopathological findings were suggestive of a blood cyst. We described a rare case of a right atrial blood cyst incidentally found during evaluation for metastatic breast cancer in a woman.