Imaging of Fatty Tumors: Distinction of Lipoma and Well-differentiated Liposarcoma

Abstract

A significant number of lipomas will have prominent non-adipose areas and will demonstrate an imaging appearance traditionally ascribed to well-differentiated liposarcoma. Features that suggest malignancy include increased patient age, large lesion size, presence of thick septa, presence of nodular and/or globular or non-adipose mass-like areas, and decreased percentage of fat composition.

A case report of an intermuscular lipoma: presentation, pathophysiology, differential diagnosis

“…In this case, the MRI measurements of the 3,16 or atypical adipocytes 17 would raise the concern for liposarcoma. Histologically, lipomas resemble normal fat, whereas well-differentiated liposarcomas, although similarly resembling 9 fat histologically, also have dense bands of collagen traversing the mass with associated gelatinous areas.…”

“…Histologically, lipomas resemble normal fat, whereas well-differentiated liposarcomas, although similarly resembling 9 fat histologically, also have dense bands of collagen traversing the mass with associated gelatinous areas. 16 Kransdorf et al 16 reported that distinguishing between a well-differentiated liposarcoma and lipoma is challenging. Magnetic resonance imaging and CT depict well-differentiated liposarcomas as having thickened septae (defined as septae greater than 2 mm thick or focal thickening) and nodular and/or globular areas of nonadipose tissue within the lesion or associated with the mass.…”

“…Nonadipose tissue comprising more than 25% of the lesion is also a feature consistent with welldifferentiated liposarcoma. 15,16 With imaging, characteristics that would exclude the diagnosis of a lipoma include thick septations, soft tissue elements, and nodular enhancing regions. 9 The MRI examination revealed none of these findings.…”

Soft tissue sarcomas at a glance: clinical, histological, and MR imaging features of malignant extremity soft tissue tumors

“…Dedifferentiation can occur in primary lesions but more often in recurrences or metastases. Dedifferentiation is seen in up to 10% of ALT/WDL, most often in RP tumors [5]. On MRI, ALT/WDL present as predominantly lipomatous tumors with thick septa (>2 mm), globular and/or nodular areas, and/or associated masses [6].…”

“…They may have large mucoid pools creating a "pulmonary edema" growth pattern. Myxoid liposarcomas often recur and metastasize to unusual locations such as the RP and the opposite extremity, even before spreading to the lungs [1,5]. On MRI tumors are characterized by lacy or linear foci of high SI within a low intensity mass on T1WI.…”