A mixed tumor of the omentum majus in an adult with discussion related to hepatoblastoma.

A mixed tumor of the omentum majus found at autopsy of a 28-year-old man with a huge liver tumor is described. The primary tumor was identified in the omentum majus by macroscopic, histologic and electron-=microscopic observations. The tumor was finally diagnosed as a mixed tumor which resembled a hepatoblastoma consisting of immature and embryonal types of epithelial component and of mesodermal tumor including hemangioma, osteoid and myxomatous tissues in the primary lesion. Widespread multiple metastases of the epithelial component mainly to the liver, and partially in the lungs, diaphragm and lymph nodes were noted. The levels of alpha-fetoprotein and carcinoembryonic antigen were within normal limits, but the epithelial component showed a resemblance to primitive hepatocytes. This tumor was discussed related to hepatoblastoma in an adult, with the features compatible with description of the same tumors reported previously in the literature.