COX-2+ myofibroblasts may play a key role in marked stromal fibrosis in strictured colorectal carcinomas

AIMS: To elucidate the mechanism of marked stromal fibrosis in strictured colorectal carcinomas (SC) that cause complete ileus. METHODS AND RESULTS: Sixteen cases of SC and 29 cases of non-strictured colorectal carcinoma (NSC) were studied. These carcinomas showed similar clinicopathological features except for bowel stricture. The stricture index (SI) showing the degree of bowel stricture was 59.8 +/- 12.1% in SC versus 20.8 +/- 24.6% in NSC (P < 0.001). The fibrosis index (FI), defined to reflect the extent of stromal fibrosis, was 56.3 +/- 8.8% in SC versus 21.9 +/- 10.6% in NSC (P < 0.001). COX-2+ myofibroblasts were detected in 13 cases (81.3%) in SC versus eight cases (27.6%) in NSC (P < 0.01). The COX-2+ myofibroblast density was 276.7 +/- 181.1 cells/mm(2) in SC versus 26.6 +/- 52.7 cells/mm(2) in NSC (P < 0.001). When all cases were divided into two groups with and without COX-2+ myofibroblasts, the SI was 48.8 +/- 19.1% in those with COX-2+ myofibroblasts versus 24.8 +/- 29.3% in those with COX-2- myofibroblasts (P < 0.001). CONCLUSION: COX-2+ myofibroblasts may play an important role in extensive bowel stricture in colorectal carcinomas.