MALIGNANT MIXED TUMOR (CARCINOSARCOMA) OF THE PANCREAS - A CASE-REPORT SUPPORTING ORGAN-INDUCED DIFFERENTIATION OF MALIGNANCY

Background. We present an unusual case of a malignant mixed tumor (car cinosarcoma) of the the concept of the head of the pancreas that was s urgically resected and whose tissue pathologic condition supported the concept of organ-induced differentiation of malignancy. Methods. Afte r a pancreaticoduodenectomy, tissue sections from various anatomic reg ions of the tumor were studied by routine histologic examination and i mmunocytochemistry. Genomic DNA from various regions of the tumor was extracted and digested with Hpa II, and a 511 bp region of the hypoxan thine phosphoribosyltransferase gene was amplified with the polymerase chain reaction to assess clonality. Results. The pathologic findings revealed areas of both adenocarcinoma and leiomyosarcoma, but these di sparate areas were not randomly distributed but rather were polar in n ature. The adenocarcinomatous areas localized to the tumor within the head of the pancreas, an area of normal ontogenetic glandular developm ent, whereas the leiomyosarcomatous areas localized to regions of the tumor infiltrating the duodenal wall, an area of normal ontogenetic sm ooth muscle development. Both the adenocarcinomatous and the leiomyosa rcomatous areas showed evidence of monoclonality and clonal identity. Conclusions. This interesting polar distribution of histologic pattern s illustrated by this malignant mixed tumor (carcinosarcoma) supports the hypothesis of organ-induced differentiation of malignancy.