Radiologic features of retroperitoneal cystic hamartoma

Retroperitoneal cystic hamartoma is a rare tumor believed to originate from small portions of the embryonic tailgut that normally disappear in early fetal development. Depending on the location and size of the mass, a wide range of clinical presentations is associated with the lesion. Most lesions are found in the presacrococcygealretrorectal space, but they may also occur in other retroperitoneal locations. Computed tomography (CT) is the most sensitive radiologic study for detecting these tumors, which usually are small, round, sharply marginated, and of homogeneous soft tissue density. We describe the clinical, radiographic, and pathologic features in four patients. In three cases, the lesions occurred in the perirectal space, and in one it was found in the iliac fossa. In this last case, there was an additional lesion in the perinephric region.