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

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

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.

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).

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.