Giant cell reaction to ameloblastoma: an immunohistochemical and ultrastructural study of a case.

Histopathologic, immunohistochemical, and ultrastructural features of the giant cells appearing in the tissue surrounding an ameloblastoma are presented. These giant cells exhibited strong activity of a highly stable form of acid phosphatase, and were positive for alpha-1-antichymotrypsin. Ultrastructurally, the cytoplasm of the giant cells contained numerous mitochondria, and the cell membrane was comparatively smooth. Therefore, it is proposed that these multinucleated giant cells are reactive to the invasion of ameloblastoma and are histiocytic in origin.