MR appearances of desmoid tumors in familial adenomatous polyposis

The purpose of this study was to investigate the ability of MR imaging to show desmoid tumors in patients with familial adenomatous polyposis, to document the appearances of these tumors, and to identify possible predictors of growth.

CT and MR imaging of 15 patients with familial adenomatous polyposis and known abdominal wall or intraabdominal desmoid tumors were performed. Nine patients underwent follow-up CT and MR imaging, and four patients had undergone CT within the previous 12 months. Unenhanced and gadolinium-enhanced T1-weighted MR imaging sequences and T2-weighted MR imaging sequences were performed, as was unenhanced and IV contrast-enhanced helical CT. The CT and MR images were independently assessed.

CT revealed 35 desmoid tumors: 22 were intraabdominal and 13 were in the abdominal wall. MR imaging revealed 21 of the 22 intraabdominal desmoid tumors and 13 of the 13 abdominal wall desmoid tumors. MR imaging and CT findings agreed precisely on the site and margin of the intraabdominal and abdominal wall desmoid tumors. CT was more effective in revealing their relationship to the bowel. Contrast enhancement was more easily identified on MR images than on CT scans, especially when enhancement was inhomogeneous. High signal intensity on T2-weighted images was seen in eight desmoid tumors, all of which showed significant growth on follow-up scans.

MR imaging can show both intraabdominal and abdominal wall desmoid tumors in patients with familial adenomatous polyposis. High signal intensity on T2-weighted images was seen from desmoid tumors that had shown marked growth on follow-up imaging.