Image Description
Introduction: Spindle cell lipoma and pleomorphic lipoma are uncommon benign lipomatous tumors that show overlapping clinical, histologic, immunohistochemical, and cytogenetic features (monosomy or partial loss of 13q or 16q). Some cases show features of pure spindle cell or pure pleomorphic lipoma. Others have areas of both within the same tumor. They appear to represent morphologic continuum of the same entity. They should not be confused with atypical lipomatous tumor/well-differentiated liposarcoma.
This image of spindle cell lipoma shows an admixture of bland spindle cells and mature univacuolated adipocytes.
About the Disease
Spindle cell and pleomorphic lipomas are uncommon benign lipomatous tumors with overlapping clinical, morphologic, and cytogenetic features. They represent morphologic continuum of the same entity. They occur in 45-60 yr. age group with a strong male predilection. Majority (80%) arise in the posterior neck, shoulder, or upper back as slow-growing, solitary, well-circumscribed, firm, painless subcutaneous nodules, usually < 5 cm in size.The morphology depends upon the relative proportion of mature adipose tissue, spindle cells, and fibromyxoid stroma. Some tumors are lipoma-like with abundant fat and only scattered foci of spindle cells. Others are grey-white firm tumors composed of spindle/pleomorphic cells with only rare foci of adipose tissue. The background stroma is fibromyxoid or collagenous with abundant mast cells and thick ropy collagen bundles. Pleomorphic lipomas resemble spindle cell lipomas but also contain floret giant cells with hyperchromatic nuclei in a wreath-like arrangement.Deletions of 13q14 (or entire chromosome 13) with loss of tumor suppressor gene RB1 are found in the majority of cases. The same deletion is also found in cellular angiofibroma and mammary and soft tissue myofibroblastomas.