Also, Ki67 labeling studies on malignant mixed mullerian tumors show the carcinomatous component to have a higher Ki67 labeling than the sarcomatous component, suggesting that the sarcomatous component is derived from the carcinoma.6,7 In contrast to malignant mixed mullerian tumor, the carcinomatous and sarcomatous components of the pancreatic carcinosarcoma in this case showed very different immunohistochemical staining profiles with the sarcomatous component having a higher Ki67 rate of approximately 90% versus the carcinomatous component with a rate of approximately 50%. This evidence concerns the gene MKI67 and carcinosarcoma.