OBJECTIVETo compare the difference in CT manifestations between primary colorectal mucinous adenocarcinoma and signet ring cell carcinoma in order to improve radiologic diagnosis.

METHODSClinicopathological data and CT findings of 109 patients with colorectal mucinous adenocarcinoma and 46 patients with primary colorectal signet-ring cell carcinoma confirmed by surgery and pathology from March 2008 to February 2015 in the Tumor Hospital of Yunnan Province were retrospectively collected. Differences in age, gender, tumor location, length and thickness of the involved intestinal wall, thickening pattern of the intestinal wall, lesion density, calcification, contrast-enhanced form, peri-intestinal invasion, occurrence of intestinal obstruction and metastasis of other organs were compared between the two groups.

RESULTSAmong 109 patients with colorectal mucinous adenocarcinoma, 68 were men and 41 were women with a mean age of (56.8±15.4) years. Among 46 patients with primary colorectal signet-ring cell carcinoma, 26 were men and 20 were women with a mean age of (42.9±15.6) years. Compared with mucinous adenocarcinoma group, signet-ring cell carcinoma group showed more concentric bowel-wall thickening[93.5%(43/46) vs. 81.6%(89/109), χ=9.19, P=0.030], higher lesion density [(42.0±3.0) Hu vs. (28.5±1.5) Hu, t=37.30, P=0.000], more marked enhancement [54.3%(25/46) vs. 12.8%(14/109), χ=35.21, P=0.000], less vast-low-density region in enhanced CT imaging[2.2%(1/46) vs. 45.0%(49/109), χ=73.31, P=0.000] and more severe peri-intestinal invasion [41.3% (19/46) vs. 17.4%(19/109), χ=10.25, P=0.006]. Calcification was found in 18.3%(20/109) of mucinous adenocarcinoma cases, but was not found in signet-ring cell carcinoma cases (χ=9.69, P=0.002). Target ring sign in contrast-enhanced scan was observed in 15.2%(7/46) of signet-ring cell carcinoma cases, while in none of mucinous adenocarcinoma cases (χ=17.37, P=0.000). There were no statistically significant differences in lesion location, length and thickness of the involved intestinal wall, occurrence of intestinal obstruction, lymph node metastasis, liver or peritoneum metastasis between two groups(all P>0.05).

CONCLUSIONSSignet-ring cell carcinoma is often found in younger patients, whose CT manifestation is characterized by the target ring sign in contrast-enhanced scan, while primary colorectal mucinous adenocarcinoma is often in older patients, whose CT manifestation is characterized by calcification in unenhanced scan and low density region in enhanced CT show.