Giant biatrial myxoma with two different gross findings.

We experienced a giant biatrial myxoma concomitant with hepatocellular carcinoma. Most of myxomas originate from the left atrium, and biatrial myxomas are extremely rare. Excision of the giant cardiac tumor was performed to avoid risks of life-threatening complications. The resected mass was grossly composed of two parts with the border of interatrial septum and with the shape of peanut shell. Although microscopic examinations revealed enlarged vessels, hemorrhages and hemosiderosis in the left part and high cellularity with chronic inflammation in the right part, spindle-shaped cells in a loose myxoid stroma were observed in both parts of the tumor, consistent with the diagnosis of myxoma. His second operation for hepatic cancer was successfully performed following 1 month after the first operation. Surgical treatment should be considered for giant atrium tumor which has risk of life-threatening complications even if patients have another cancer.