Intraductal carcinosarcoma with a heterologous mesenchymal component originating in intraductal papillary-mucinous carcinoma (IPMC) of the pancreas with both carcinoma and osteosarcoma cells arising from IPMC cells.

Carcinosarcoma of the pancreas is extremely rare and its histogenesis is still unclear. This is a report on a 64-year-old female patient with an intraductal carcinosarcoma arising from intraductal papillary-mucinous carcinoma (IPMC) in the pancreas tail. The carcinosarcoma grew as a polypoid mass within the main pancreatic duct. Histologically, the tumour consisted of adenocarcinoma covering the luminal surface of the lesion with minimal stromal invasion, and osteosarcoma occupying the stroma. Immunohistochemical and gene mutation analyses revealed that both the carcinomatous and sarcomatous tumour cells of the carcinosarcoma, as well as the IPMC cells, expressed TP53 and had identical mutations in KRAS and TP53 genes, indicating that these two neoplastic components of the carcinosarcoma shared a common tumorigenesis and arose from the IPMC. This is the first report of a carcinosarcoma originating in IPMC. These findings imply that carcinosarcoma with a heterologous mesenchymal component is of ductal origin.