Carcinosarcoma of the gallbladder. Report of a case and review of the literature.

An extremely rare case of carcinosarcoma of the gallbladder is reported. The tumor presenting as a large, soft polypoid growth was microscopically characterized by an admixture of adenocarcinomatous and sarcomatous elements, the latter containing specific heterologous mesenchymal elements such as osteoid, cartilage, and rhabdomyoblasts. The cytoplasm of neoplastic rhabdomyoblasts offered unequivocal cross striations and was strongly positive for myoglobin, determined by the immunoperoxidase procedure. Metastatic tumors in the liver also exhibited a dual composition of adenocarcinoma and rhabdomyosarcoma. This appears to be the second documented case of this type of neoplasm with the rhabdomyosarcomatous component. The clinical settings and morbid prognosis were similar to events in cases of carcinoma of the gallbladder.