Carcinoma of pancreas simulating giant cell tumor of bone. Electron-microscopic evidence of its acinar cell origin

Abstract

Two cases of a previously undescribed tumor were studied. The lesion is a primary pancreatic neoplasm, which by light microscopy has an appearance indistinguishable from that of a giant cell tumor of bone. Electron microscopy was done in one of the two cases. Both giant and “stromal” cells have abundant granular endoplasmic reticulum containing intracisternal granules of proteic nature similar to those described in pancreatic acinar cells. Microvilli are present in the giant cells, and numerous desmosomes are found between the “stromal” cells. These features are strongly suggestive that epithelial—and specifically acinar—elements are the cells of origin of the tumor.