CT features of primary colorectal signet-ring cell carcinoma

PURPOSE: The purpose of this work was to evaluate the CT features of 15 patients with primary colorectal signet-ring cell carcinomas. METHOD: We retrospectively reviewed the CT scans of 15 patients (mean age 44 years) with pathologically proved colorectal signet-ring cell carcinoma. On CT, we evaluated the site and length of the tumor, bowel wall thickening patterns, perirectal or pericolic infiltration, the presence or absence of colonic obstruction, and metastasis to other organs. RESULTS: The tumors were located in the rectum in nine patients, the sigmoid colon in one, the hepatic flexure in one, the transverse colon in one, the ascending colon in two, and the cecum in one. The tumor length ranged from 4.0 to 10.0 cm (mean 6.1 cm) with mean thickness of 2.1 cm. CT showed concentric bowel wall thickening in all patients ("even" in 8 and "uneven" in 7), target appearance was noted in 4, perirectal or pericolic infiltrations were moderate to severe in 12, and colorectal obstruction was seen in 6. In the tumor spread patterns, lymphadenopathy was noted in 13, invasion to adjacent pelvic organs in 5, peritoneal carcinomatosis in 4, liver metastasis in 2, and periureteric metastasis in 1. CONCLUSION: Primary signet-ring cell colorectal carcinoma should be included for differential consideration when CT shows a long length of concentric bowel wall thickening and target sign, especially when such findings occur in the rectum and in young patients.