GIANT-CELLS IN PIGMENTED VILLE NODULAR SYNOVITIS EXPRESS AN OSTEOCLAST PHENOTYPE

Aim-To determine the cytochemical and functional phenotype of multinuc leated giant cells in pigmented ville nodular synovitis (PVNS). Method s-Giant cells isolated from a patient with PVNS of the knee were asses sed for a number of markers used to distinguish osteoclasts from macro phages/macrophage polykaryons: evidence of tartrate resistant acid pho sphatase (TRAP) activity; expression of CD11b, CD14, CD51, and calcito nin receptors; and the ability of the giant cells to carry out lacunar resorption. Results-Isolated giant cells expressed an osteoclast anti genic phenotype (positive for CD51, negative for CD11b and CD14) and w ere TRAP and calcitonin receptor positive. They also showed functional evidence of osteoclast differentiation, producing numerous lacunar bo ne resorption pits on bone slices in short term culture. Conclusions-T he giant cells in this case of PVNS express all the phenotypical featu res of osteoclasts including the ability to carry out lacunar resorpti on. This may account for the bone destruction associated with this agg ressive synovial lesion.