Malignant lymphoma arising in cardiac myxoma, presenting with peripheral arterial emboli.

Composite tumors of cardiac myxoma and malignant lymphoma are extremely rare, with 11 of such cases reported in the literature. A 44-year-old man presented to us with abrupt right lower leg pain. A computed tomography angiogram revealed segmental obstruction of the right common femoral artery, and embolectomy was performed. The embolectomy specimen contained several clusters of degenerated round/oval atypical cells in the fibrinous or myxoid background. Immunohistochemical examination revealed that these atypical cells were negative for cytokeratin and non-specifically expressed CD45. After one year of follow-up, the patient presented with dyspnea on exertion. Transthoracic echocardiography revealed a 5.7×1.9 cm, lobulated, echogenic, intracardiac mass, and excision was performed. Microscopically, most of the mass was composed of stellate or curved cells with eosinophilic cytoplasm in the myxoid background. However, several clusters or scattered round/oval atypical cells, similar to those observed in the embolectomy specimen, were observed. These atypical cells were positive for CD45 and CD20, with a Ki-67 labeling index of 90%. Calretinin was expressed in stellate cells but not in atypical cells. Therefore, we made a diagnosis of diffuse large B cell lymphoma (DLBCL) arising in the cardiac myxoma. Our case is an extremely rare example of a composite tumor of cardiac myxoma and DLBCL presenting with peripheral arterial emboli. Thorough histological evaluation of embolectomy and cardiac myxoma specimen is crucial for the diagnosis of composite tumor.