Undiff. Pleomorphic Sarcoma: Microscopic

Microscopic Features: In most cases of undifferentiated pleomorphic sarcoma, the stroma consists of delicate collagen fibrils surrounding individual tumor cells. However, in some cases, there is extensive collagen deposition (see next two images).

Rarely, there may be metaplastic osteoid or chondroid matrix. Depending upon the amount and appearance, such cases are more appropriately diagnosed as osteosarcoma or chondrosarcoma.