Malignant mesenchymoma: a very rare tumor of the peritoneum. Case report with a review of the literature.

We report the case of an 82-year-old male patient with a malignant mesenchymoma. The tumor arose from the parietal peritoneum closely attached to the ascending colon. It consisted of a larger liposarcomatous and a smaller leiomyosarcomatous component which was demonstrated by immunohistochemistry. To our knowledge this is the first report of a malignant mesenchymoma of this histological composition originating from the parietal peritoneum. The tumor was completely removed surgically, which is the treatment of choice for such tumors. In agreement with other authors, we believe that malignant mesenchymomas arise from a primitive mesenchymal cell with the capacity for totipotent differentiation.