There are a variety of fat-containing lesions that can arise in the intraperitoneal cavity and retroperitoneal space. Some of these fat-containing lesions, such as liposarcoma and retroperitoneal teratoma, have to be resected, although resection can be deferred for others, such as adrenal adenoma, myelolipoma, angiomyolipoma, ovarian teratoma, and lipoma, until the lesions become large or symptomatic. The third group tumors (i.e., mesenteric panniculitis and pseudolipoma of Glisson's capsule) require medical treatment or no treatment at all. Identifying factors such as whether the fat is macroscopic or microscopic within the lesion, the origin of the lesions, and the presence of combined calcification is important for narrowing the differential diagnosis. The development and wide-spread use of modern imaging modalities make identification of these factors easier so narrowing the differential diagnosis is possible. At the same time, lesions that do not require immediate treatment are being incidentally found at an increasing rate with these same imaging techniques. Thus, the questions about the treatment methods have become increasingly important. Classifying lesions in terms of the necessity of performing surgical treatment can provide important information to clinicians, and this is the one of a radiologist's key responsibilities.
Abdominal Fat/pathology/radiography ; Adult ; Aged ; Diagnosis, Differential ; Female ; Humans ; Magnetic Resonance Imaging/methods ; Male ; Middle Aged ; Neoplasms, Adipose Tissue/*pathology/*radiography ; Peritoneal Cavity/pathology/radiography ; Peritoneal Diseases/pathology/radiography ; Peritoneal Neoplasms/*pathology/*radiography ; Retroperitoneal Neoplasms/*pathology/*radiography ; Retroperitoneal Space/pathology/radiography ; Tomography, Spiral Computed/methods ; Young Adult