A desmoid tumor is composed of fibroblasts. Histologically, the tumor is benign and does not metastasize, but it is locally aggressive, inliltrates contiguous structures, and tends to recur after resection.
Desmoid tumors may occur at any age, but most often they are seen in the third and fourth decades.
Imaging and Location
On cross-sectional imaging, desmoids have well-defined borders two thirds of the time, but the rest of the time the margins are infiltrative and poorly defined. CT scans obtained without contrast enhancement show variable attenuation relative to muscle. After IV contrast administration, desmoid tumors may or may not enhance. Most are hyperdense or isodense with muscle on contrast-enhanced scans.
Desmoid tumors have a signal intensity lower than that of muscle on TI-weighted MR images, with variable signal intensity on T2-weighted images. They may have an aggressive appearance and be confused with a malignant tumor. The presence of areas of low signal intensity on both TI-weighted and T2-weighted images, resulting from fibrous tissue, is a clue to the correct diagnosis