Early undifferentiated pancreatic carcinoma with osteoclastlike giant cells: direct evidence for ductal evolution.

Undifferentiated (anaplastic) carcinomas of the pancreas are rare. To a variable degree, they may contain osteoclastlike giant cells and are then sometimes referred to as osteoclastlike giant cell tumors. The histogenesis of these tumors has been discussed with great controversy. Thus, as a result from numerous histomorphologic, immunohistochemical, ultrastructural, and molecular examinations, frequently performed as single case studies, it has been concluded that undifferentiated carcinomas and osteoclastlike giant cell tumors of the pancreas originate from epithelial cells, mesenchymal cells, undifferentiated precursor cells, or stem cells. However, to date, early stage tumors have not been described, most likely because of the fact that at the time of diagnosis the tumors have commonly reached advanced stages with large tumor size. In this report, we present the case of an undifferentiated pancreatic carcinoma with osteoclastlike giant cells, which was incidentally detected at a very early stage in a pancreatitis specimen. Our histomorphologic and immunohistochemical findings not only provide evidence for a ductal origin, but for the first time document initial steps in the evolution of these tumors. Therefore, we suggest that the tumor should be considered as an anaplastic variant of pancreatic ductal adenocarcinoma.