[Periosteal osteosarcoma of the femur: a pathological and ultrastructural study].

A femoral, diaphyseal tumor was found in a 17-year old male, and the diagnosis of periosteal osteosarcoma was made, based on the typical radiological and pathological findings. Microscopic observation on a resected specimen revealed that the tumor was covered with the intact periosteal fibrous layer and did not extend beyond the periosteum. The adjacent cortex was free of tumor. These findings indicated that the tumor originated from the periosteal cambium layer, which lies between the periosteal fibrous layer and the cortex. For transmission electron microscopic examination, the tissue was obtained at open biopsy. Ultrastructurally, no specific cell of periosteal osteosarcoma was found. Although most types of osteosarcoma cells were identified in the tumor (osteoblast-like, chondroblast-like, fibroblast-like, primitive mesenchymal-like, osteoclast-like and so on), the ultrastructural characteristics were of wide variety and of low malignancy.