The osteoclast-type giant cell tumor of the pancreas.

We present a case report of osteoclast-type giant cell tumor of the pancreas and review the literature concerning this rare neoplasm, the histogenesis of which is uncertain. Electron microscopic features have suggested stromal, histiocytic, and epithelial origins to different investigators. Analysis of the present case supports and epithelial origin, with positive immunocytochemical staining for carcinoembryonic antigen and for low molecular weight keratin in the mononuclear and in some osteoclastlike giant cells. These tumor cells did not stain for mesenchymal markers (lysozyme, alpha 1-antitrypsin, alpha 1-antichymotrypsin, S100 protein). Zymogen granules, desmosomes, and zonulae occludentes were identified ultrastructurally and further support an epithelial derivation.