这个大的肉质样肿块发生于腹膜后，属于肉瘤，来源于间叶组织。图为：恶性纤维组织细胞瘤。
This large fleshy mass arose in the retroperitoneum and is an example of a sarcoma. Sarcomas arise from mesenchymal tissues. This one happened to be a "malignant fibrous histiocytoma" which is a wastebasket term for sarcomas that do not resemble mesenchymal cells such as striated muscle (rhabdomyosarcoma), smooth muscle (leiomyosarcoma), fat (liposarcoma), blood vessels (angiosarcoma), bone (osteosarcoma), or cartilage (chondrosarcoma). Sarcomas are big and bad.