The osteoclast: review of ultrastructure, origin, and structure-function relationship.

Multinucleated cells of the giant cell tumor and the genuine osteoclasts exhibit a number of common morphological characteristics and may or may not originate from similar progenitor cells. Judging from the present preliminary results, it is obvious that the differentiation of the plasma membrane into a specialized area, the ruffled border, is not as conspicuous in the giant cell as in the osteoclast. A series of interrelated investigations including histochemical methods at the ultrastructural level applied both in giant cell tissue and cultured giant tumor cells are in progress. These studies may further elucidate the possible relationship between the osteoclast and the multinucleated giant cell tumor as well as the possible relationships between giant cells and other cell types of tumors.