Abstract

Spindle cell lipoma is a benign soft tissue tumor composed of mature adipocytes, uniform spindle cells, and collagen bundles. Clinically, it tends to presents as a solitary, well-circumscribed, painless, slow-growing, subcutaneous mass on the shoulder, back, or posterior neck of a middle-aged man. Recurrence of a spindle cell lipoma after excision is unusual. We present a case of a 37-year-old man with a spindle cell lipoma on the posterior neck that recurred twice. All three lesions had a varied histopathologic appearance. The primary lesion demonstrated classic features of a spindle cell lipoma. The first recurrence showed a predominance of adipocytes with only a subtle component of spindle cells, resembling a conventional lipoma. In addition to mature adipocytes and spindle cells, the second recurrence was characterized by a myxoid stroma and prominent follicular lymphoid hyperplasia. The tumor stained strongly for CD34 and showed focal loss of RB1 expression. FISH studies did not show rearrangement of DDIT3 or amplification of MDM2. The lymphoid hyperplasia was composed of CD20-positive B cells with some CD3-positive T cells. PCR studies for T-cell receptor and immunoglobulin heavy chain gene rearrangement did not show evidence of clonality. A recently published report described a similar case of a spindle cell lipoma with florid follicular lymphoid hyperplasia. The occurrence of two cases with nearly identical findings suggests that spindle cell lipoma with florid follicular lymphoid hyperplasia may represent a distinct variant of spindle cell lipoma and not just a serendipitous association.