Sarcomatoid carcinoma is rarely diagnosed as gallbladder cancer. Its aggressive nature, due to the characteristics of both sarcoma and carcinoma, results in a poor prognosis. We report a case of gallbladder sarcomatoid carcinoma in an 82-year-old male who was referred to our hospital for evaluation of gallbladder cancer observed on abdominopelvic computed tomography. The characteristics of the cancer were not confirmed after several imaging modalities. The surgically resected tumor was positive for both cytokeratin and vimentin as revealed via immunohistochemical staining, and a sarcomatoid carcinoma was finally diagnosed. The role of chemotherapy has not yet been identified. Therefore, radiation therapy is planned to reduce the risk of recurrence.

Malignant transformation of mature cystic teratoma (MCT) is rare. Sarcomatoid carcinoma is a neoplasm comprising malignant mesenchymal cells and a conventional carcinomatous area. Here, we report on a case of sarcomatoid carcinoma arising from an MCT in the left ovary of a 45-year-old female. A unilocular cyst consistent with MCT was observed; however, a nodule within the cyst was confirmed from the resected ovary. Microscopically, the nodule showed both squamous cell carcinoma and pleomorphic sarcomatous components admixing with each other. Lining epithelial cells at the periphery of the main tumor showed squamous metaplasia. When a sarcomatous component is observed in the ovary tumor, it is important to find a squamous cell component, either benign or malignant.