Adamantinoma of the tibia. An ultrastructural and immunohistochemical study.

The light microscopic, ultrastructural, and immunohistochemical characteristics of two tibial adamantinomas are presented. The immunohistochemical studies utilized specific antibodies against Factor VIII-related antigen and keratin protein, considered as markers for endothelial and epithelial cells, respectively. These revealed positive staining for keratin in the tumor cells of both cases, whereas Factor VIII was not found in either. Ultrastructurally, both tumors had tonofilaments, desmosomes, gap junctions, microvillous-like projections, and basement membranes. Patient 1 had disease that was histologically of the classic spindle cell type; the disease of Patient 2 was atypical and closely resembled an epithelioid angiosarcoma. Immunohistochemical and ultrastructural findings in each case indicate an epithelial component in tibial adamantinoma.