Mixed pleomorphic-osteoclast-like tumor of the pancreas. Light microscopical, immunohistochemical, and molecular biological studies.

The morphological, immunohistochemical, and molecular biological features of a case of giant cell tumor of the pancreas are described. This neoplasm showed mononuclear and multinucleated tumor giant cells as well as numerous osteoclast-like cells with multiple foci of osteoid-osseous metaplasia. The pleomorphic and osteoclastic giant cells displayed extensive homologies in their immunohistochemical profiles. Neither the pleomorphic nor osteoclast-like portion of the tumor showed neither c-Ki-ras nor p53 mutation and did not express the mutated p53 protein. The results suggest that the pleomorphic and osteoclast-like components are histogenetically related and that this rare neoplasm originates from a precursor cell capable of differentiating along divergent cell type.