Colorectal cancer in inflammatory bowel diseases: CT features with pathological correlation.

Purpose: To describe CT features of inflammatory bowel disease (IBD)-related colorectal cancer and correlate the imaging findings with histopathological findings.

Materials And Methods: CT imaging findings in 17 patients with IBD-related colorectal cancer were retrospectively evaluated. Imaging findings were correlated with surgical and histopathological findings. Univariate and multivariate analyses explored the relationships between CT and histopathological variables.

Results: Two different CT patterns were individualized including clearly visible soft tissue mass (8/17; 47%) (Type 1 tumor) or stenosis with marked circumferential thickening resembling inflammation (9/17; 53%) (Type 2 tumor). At univariate analysis, thickness of tumor-free colorectal wall at CT was greater in Crohn disease (median, 13 mm) than in ulcerative colitis (median, 7 mm) (P = 0.011). Significant association was found between presence of signet ring cells and Type 2 tumor at CT (6/9, 67% P = 0.009) and colonic dilatation proximal to tumor (5/6, 83%; P = 0.035). At multivariate analysis, free-fluid effusion was the single independent CT variable predictive for the presence of signet ring cells (odds ratio = 50; 95% CI 2.56-977.02; P = 0.01).

Conclusion: Colorectal cancer in IBD displays two main features on CT. Type 2 tumors and free-fluid effusion correlate with presence of signet ring cells. Knowledge of these findings is critical to help suggest the diagnosis.