High alkaline phosphatase activity of telangiectatic osteosarcoma (TOS) and its diagnostic significance

Telangiectatic osteosarcoma (TOS) which occurred in the metaphysis of the right femoral bone in a 13-year-old female was reported. It showed osteolytic and cystic lesion without sclerotic change on roentgenogram and consisted histologically of various sized blood-filled spaces lined by layers of round to oval tumor cells in the thin fibrous septa. In some solid areas, a proliferation of atypical tumor cells with large prominent nucleoli was evident, embedded in the lace-like osteoid tissue. Mitotic cells were easily encountered. A large population of tumor cells revealed high alkaline phosphatase activity as well as 5'-nucleotidase activity, indicative of osteogenic cell origin. Ultrastructurally, they showed osteogenic characteristics of well-developed rough endoplasmic reticula, cytoplasmic microfibrils, and dense bodies, but not for those of endothelial cells. In this report, we suggest that alkaline phosphatase activity in biopsy and surgical specimens is useful for distinguishing TOS from other osteolytic bone tumors, with regard to its ontogenic discussion.