A 40-year-old pregnant woman who had previously been diagnosed with uterine myoma underwent cesarean section. During the operation, a tumor thought to be uterine myoma was found to be an extrauterine tumor arising from the upper abdomen. After the delivery of the fetus, a staging CT scan was performed, which revealed a huge, 18 cm, hepatic tumor in the left lateral segment, a mediastinal tumor with calcification, and multiple lung nodules. She underwent a left hepatic lobectomy and a wedge resection 8 days after the delivery. The initial pathological diagnosis was moderately differentiated neuroendocrine tumor (NET). However, as a primary hepatic NET is extremely rare, further immunohistochemical staining was performed. The tumor was positive for p63, CD5, c-kit, and bcl-2, indicating a diagnosis of thymic carcinoma with liver and lung metastases.