Osteoclast-like giant cell tumor of the pancreas associated with mucus-secreting adenocarcinoma

Background/Aims: The osteoclast-like giant cell tumor of the pancreas is a rare entity that closely resembles giant cell tumor of the bone, which has also been observed in many other organs. Some tumors also contain areas of ductal adenocarcinoma. Conflicting opinions exist regarding the tumor origin, whether it is mesenchymal or epithelial, neoplastic or reactive. Methods: We report the case of a 69-year-old Brazilian man with a mass in the head of the pancreas, the histological examination of which revealed a predominant component of osteoclast-like giant cells within a background of pleomorphic mononuclear cells with osteoid formation and other areas composed of conventional mucus-secreting adenocarcinoma. Results: Immunohistochemistry showed that carcinoma cells of the usual type expressed epithelial antigens (EMA and cytokeratin) and lysozyme; the giant cells expressed vimentin, CD45, CD68, and lysozyme; and the mononuclear cells expressed macrophage marker (HAM56), vimentin, and lysozyme, and only some of them expressed epithelial markers, CD45, and CD68. Conclusion: Our immunohistochemical findings reveal that the giant cells in this case are of mesen-chymal origin may be from the bone marrow cells. We believe that it is important to determine the histogenesis in each case to carry out the pertinent adjuvant therapy.