Answer: Lympedema

Histology: The specimen consists of fat with thickened interlobular septa containing reactive fibroblasts. The focal atypia within the fibroblasts, as well as the thickened septa, mimic the cytoarchitectural features of Lipoma-like Liposarcoma. Histologic clues to the diagnosis include the absence of true lipoblasts, as well as the presence of lymphedema in the overlying skin (epidermal thickening, lymphangiectasia, dermal fibrosis, and chronic inflammation).

Discussion: Fat-predominant Angiomyolipoma is a known mimic of Liposarcoma; however, the absence of dysplastic blood vessels or epithelioid smooth muscle precludes this diagnosis. The absence of histiocytic reaction and the septal distribution of the atypical cells argue against fat necrosis. Well differentiated Liposarcoma typically lacks septal edema and would feature well-formed lipoblasts.

Reference(s):
– Am J Surg Pathol 1998; 22: 1277-1283.