Gastrointestinal: Giant liposarcoma

What abnormalities are seen on the computed tomography scan shown in Fig. 1? The major abnormality is a large mass on the right side of the abdomen that displaces other organs to the left and displaces the right kidney inferiorly. The mass has a slightly heterogeneous appearance with an attenuation consistent with fat. The fatty nature of the mass was supported by the loss of signal using an axial fat suppression T2-weighted magnetic resonance image. The patient was a woman, aged 72, who was admitted to hospital because of epigastric discomfort, abdominal distension and weight loss. On examination, she had a large mass in the right abdomen. A plain abdominal radiograph showed displacement of most of the bowel into the left flank. At laparotomy, the mass was well-circumscribed, pale in color and had areas of nodularity. The appearance of the resected specimen is shown in Fig. 2. The histological diagnosis was that of a well-differentiated ‘lipoma-like’ liposarcoma.

Liposarcomas are soft tissue tumors that differentiate towards adipose tissue. Histologically, they can be classified in increasing order of malignancy as well-differentiated, myxoid, pleomorphic and round cell subtypes. Some specimens contain multiple histological subtypes within the same tumor. For example, one component can be an atypical lipomatous tumor while other areas have features of a cellular, non-lipogenic sarcoma (the dedifferentiated component). Although most lipomas are located in subcutaneous tissues, liposarcomas usually occur in central body sites, particularly the retroperitoneum. Computed tomography and magnetic resonance scans can predict the presence of well-differentiated liposarcomas as these tumors have an attenuation and signal intensity that is similar to that of fat. However, in contrast to lipomas, liposarcomas often show fibrous septa that are thicker and more irregular, sometimes with nodular components. Well-differentiated ‘lipoma-like’ liposarcomas can recur locally if incompletely excised but do not metastasize.

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