A case of 'fat-free' pleomorphic lipoma occurring in the upper back and axilla simultaneously

Pleomorphic lipoma is a rare neoplasm that predominantly occurs in the dermis or subcutis of the posterior neck, upper back, and shoulders. Although pleomorphic lipoma is a benign tumor, it may contain atypical cells. As a variant of spindle cell lipoma, pleomorphic lipoma clinically presents as a slow-growing and well-circumscribed subcutaneous mass. Rarely, some patients have multiple lesions. Histologically, pleomorphic lipoma is composed of mature fat, bland spindle-shaped mesenchymal cells, and coarse 'rope-like' collagen bands. In addition, lipoma contains multinucleated floret-like giant cells. Although spindle cell lipoma/pleomorphic lipoma with little fat was seen in the original series described by Enzinger and Harvey, cases with little to no fat remain diagnostically challenging. Herein, we report a case of 'fat-free' pleomorphic lipoma occurring in the upper back and axilla simultaneously. Although the lipoma was typically composed of bland spindle-shaped cells, rope-like collagen, scattered floret-like giant cells, and striking stromal myxoid change in the background, mature fat was absent. Immunohistochemical analyses showed positive staining for CD34, vimentin, and Bcl-2, and negative staining for S100, confirming the diagnosis of pleomorphic lipoma.