Primary cardiac rhabdomyosarcoma developed after receiving radiotherapy for left breast cancer 18 years prior.

The heart is an organ where primary malignant tumors rarely develop. In particular, the incidence of cardiac rhabdomyosarcoma (RMS) is extremely low. It has been reported that the risk of second malignant tumors in mediastinum is increased by radiotherapy in women with breast cancer. However, little is known about the association between irradiation to heart and cardiac RMS. Here, we report a case of a 68-year-old woman with primary cardiac RMS. She suddenly presented syncope at a workplace, and was taken to the emergency room at our hospital. Several imaging tests, including echocardiogram and cine magnetic resonance imaging, detected two tumors in the right ventricle (RV) and its outflow tract, which had almost obstructed the main trunk of the pulmonary artery (PA). To avoid sudden PA occlusion by the tumor, we emergently performed surgical excision of the tumors from the RV. Pathological analysis revealed that these tumors were embryonal type RMS. She had received radiotherapy after mastectomy for left breast cancer 18 years previously, and no recurrence of breast cancer had been detected. This cardiac RMS is considered as a second malignant tumor related to radiotherapy for breast cancer.