Mixed mesenchymal tumours of the mouse uterus.

Mixed mesenchymal neoplasms of the uterus of 8 mice had either leiomyosarcoma or fibrosarcoma components. 6 had osteoid and 2 had both vacuolated and undifferentiated neoplastic cells. The putative chondrosarcoma component varied from a poorly-differentiated appearance (sheet-like masses of cells) to a myxoid appearance with giant cells and cells with cytoplasmic vacuoles. 1 tumour contained well-differentiated bone that was located within the primary and just beneath the splenic capsule. In another tumour composed of osteosarcoma, chondrosarcoma and fibrosarcoma, the latter component had invaded the wall of the rectum.