Herein is presented a case of carcinosarcoma of the pancreas in an 82-year-old woman, analyzed on immunohistochemistry and K-ras sequence. The tumor, which arose in the pancreas head, was removed on pancreaticoduodenectomy. The patient died, however, of disseminated intravascular coagulation syndrome from postoperative sepsis 13 days later. Microscopically, the tumor consisted of malignant epithelial (well-differentiated adenocarcinoma cells) and mesenchymal (spindle-shaped tumor cells) components. The adenocarcinoma cells had positive immunostaining for cytokeratin AE1/AE3, cytokeratin 7, epithelial membrane antigen (EMA), CEA and carbohydrate antigen 19-9 (CA 19-9), while focal staining of these proteins was observed in the sarcomatous cells. In contrast, the sarcomatous cells had diffuse immunostaining for vimentin, CD10 and p53, while these proteins were not expressed in the ductal adenocarcinoma cells. These findings support the dual characteristics of a carcinosarcoma. DNA sequencing of the present case indicated point mutations of K-ras in both codons 12 and 34 on exon 2. The latter mutation is likely to correlate with the sarcomatous characteristics of this tumor. The tumor cells had specific and diffuse positive staining for CD10 and p53, with features characteristic of rapid growth.