Giant cell tumor of bone. Fine structural localization of alkaline phosphatase

The fine structural localization of nonspecific alkaline phosphatase was elucidated in two giant cell tumors of bone using lead as capturing ion and beta-glycerophosphate as substrate in the incubation solution. Lead phosphate precipitate--indicating presence of alkaline phosphatase--was demonstrated on the plasma membranes, and the membranes bordering vesicles and vacuoles of presumed endocytotic nature, in giant cells and type 1 stromal cells (fibroblast-like cells). The findings support the view that stromal cells type I and giant cells are histogenetically related.