Malignant peritoneal mesothelioma as a pelvic mass. Application of athymic mice in clinical pathology

We reported herein an unusual presentation of malignant peritoneal mesothelioma which appeared as a solid pelvic tumor in a 73-year-old man. The solid tumor was confined in the pelvic cavity, except for one tiny disseminated nodule on the mesocolon. The pelvic tumor was resected with whole pelvic organs en bloc. Histologically, the tumor consisted of tubular and sarcomatous structures, suggesting the biphasic malignant mesothelioma. One of the transplanted tumors in athymic mice was cystic and its histology had striking similarities to cystic mesothelioma. Transplantation of human neoplasms to athymic mice may be able to reproduce histological diversity of the tumor, even if it is not fully expressed in the original tumor.