School of Podiatric Medicine - Student Research

Document Type

Poster

Publication Date

2-24-2026

Abstract

Statement of Purpose: This case presents a rare sclerosing-type atypical lipomatous tumor with myxomatous features—the first and only known reported case of an ALT in the foot—along with its pathology, treatment, and management.

Case Study: Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) represents the most common liposarcoma subtype, with recurrence and dedifferentiation risk influenced by tumor location. Retroperitoneal tumors recur frequently, while those in the lower extremity rarely do. Liposarcoma of the foot is exceedingly rare.

A 61-year-old male presented with a slowly enlarging, mildly tender lump on the right plantar heel. Radiographs demonstrated a 3 cm oval soft-tissue thickening without calcification. MRI revealed a 2.7 × 3.4 × 1.8 cm well-circumscribed subcutaneous lesion in the calcaneal fat pad, T1 hypointense, T2 hyperintense, and showing inhomogeneous post-contrast enhancement, with no invasion of plantar musculature or osseous structures. After 8 months of conservative observation, the patient elected excision due to progressive growth and discomfort. A 5 cm lazy-S incision exposed a 4.2 × 3.2 cm encapsulated mass. The lesion was widely excised with 1 cm margins, and both the mass and peripheral tissue were submitted for pathological analysis. Layered closure and a short CAM walker were applied, with two weeks non–weight-bearing with crutches followed by progressive loading.

Results: Gross pathology revealed a 3.6 × 2.8 × 1.8 cm glistening, ovoid mass weighing 11 grams. Microscopic examination confirmed the diagnosis of an atypical lipomatous tumor, sclerosing subtype, with prominent myxomatous features. Histological sections demonstrated small adipocytes surrounded by myxomatous stroma and irregular fibrous connective tissue. Trichrome and Alcian blue staining highlighted collagen and myxoid components, respectively. Immunohistochemical analysis revealed negative staining for S100, epithelial membrane antigen (EMA), desmin, and synaptophysin, but positive for MDM2, confirming the diagnosis. Importantly, there was no evidence of dedifferentiation or metastatic behavior, supporting the benign nature of the lesion. By four weeks postoperatively, the patient ambulated comfortably in regular footwear. At four-month follow-up, he remained asymptomatic with no signs of recurrence.

Analysis & Discussion: Surgical excision served as both a curative and diagnostic intervention for a plantar soft tissue mass that was ultimately confirmed as an ALT. Intraoperatively, the mass appeared encapsulated with mixed fibrous and fatty features. Histopathology revealed fibrous septae, collagen deposition, and myxoid stroma, consistent with a sclerosing variant of ALT. Immunohistochemistry with MDM2 further supported the diagnosis by demonstrating p53 inactivation through MDM2 overexpression.

ALT/WDLs are distinguished from lipomas by the presence of atypical adipocytes and higher recurrence potential. Unlike lipomas, which rarely require intervention and show minimal recurrence, ALTs necessitate closer monitoring due to the risk of transformation into DDL (Dedifferentiated Liposarcoma). Treatment selection depends on tumor size, location, and malignant potential. Literature suggests suction-assisted lipectomy for tumors < 10 cm and open surgical excision for those >10 cm or with risk of dedifferentiation.

Definitive diagnosis required a multifaceted approach, integrating clinical evaluation, imaging, surgical excision, and pathological assessment. Importantly, histological and immunohistochemical analysis remain the gold standard for distinguishing ALT from the benign lipoma.

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