Focal lymphoid hyperplasia in a lipoma, mimicking liposarcoma.

Lipomas may contain nonadipose tissue, which can confound the correct imaging diagnosis because features of such neoplasms can mimic findings associated with well-differentiated liposarcomas. Intratumoral nonadipose tissue, such as muscle, cartilage, and fibrous tissue, may be present in lipomas; however, lymphoid hyperplasia in a lipoma is extremely rare. This report describes a case involving a heterogeneous lipoma in a 55-year-old woman in whom the heterogeneous portion of the tumor was in fact a reactive lymphoid hyperplasia encased by the lipoma. The imaging features of this lesion as well as pathological findings of this unusual tumor are discussed.