Spindle Cell and Pleomorphic Lipoma
Amitabh Srivastava, MD
Key Facts
Terminology
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Benign adipocytic tumors with variable admixture of spindle cells, mucinous stroma, ropey collagen, and multinucleate giant cells
Clinical Issues
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Typically in older men (> 50 years)
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Shoulder and posterior neck most common sites
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Benign behavior
Macroscopic Features
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Well-circumscribed subcutaneous lesions
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Yellow-gray white, firm with myxoid areas
Microscopic Pathology
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Spindle cells with ropey collagen, mature adipose tissue, and myxoid stroma with mast cells
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Spindle cells are diffusely/strongly positive for CD34
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Pleomorphic lipoma shows multinucleated tumor giant cells with peripheral nuclei (“floret” cells)
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Lipoblasts may be present in some PL
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Variants
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Pseudoangiomatoid variant of SCL shows prominent slit-like spaces resembling vascular channels
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Spindle cell proliferation dominates the picture in fat-free and fat-poor variant of SCL
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Ancillary Tests
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Deletions of 16q and 13q occur in SCL/PL
Top Differential Diagnoses
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Dermatofibrosarcoma protuberans (DFSP)
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Peripheral nerve sheath tumors
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Solitary fibrous tumor (SFT)
TERMINOLOGY
Abbreviations
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Spindle cell lipoma (SCL)/pleomorphic lipoma (PL)
Definitions
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Benign adipocytic tumor with variable admixture of spindle cells, ropey collagen, and multinucleated tumor giant cells
CLINICAL ISSUES
Epidemiology
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Age
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Typically in older age group (> 50 years)
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Gender
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Predominantly in men; < 10% in women
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Site
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Shoulder and posterior neck most common sites of involvement
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Other sites
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Upper arm
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Face
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Oral cavity
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Lower extremity involvement is rare
Presentation
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Painless mass
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Dermal or subcutaneous nodule
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Often present for long duration
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Rarely multiple or familial
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Treatment
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Conservative surgical excision is adequate
Prognosis
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Benign behavior
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Local recurrence is rare
MACROSCOPIC FEATURES
Gross Appearance
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Well-circumscribed tumor
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Yellow-gray white appearance
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Firm consistency
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Some cases may show myxoid appearance
MICROSCOPIC PATHOLOGY
Histologic Features
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Spindle cell lipoma is composed of variable admixture of 3 components
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Mature adipocytes
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Bland spindle cell proliferation
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Myxoid stroma with ropey collagen and mast cells
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Pleomorphic lipoma is part of same spectrum
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In addition to above features, also shows multinucleated tumor giant cells with peripherally arranged nuclei (“floret cells”)
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Lipoblasts may be present in pleomorphic lipoma
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Cytologic Features
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Bland nuclei in spindle cell lipoma
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Hyperchromatic nuclei in multinucleated tumor giant cells in pleomorphic lipoma
Variants
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Pseudoangiomatoid variants
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Prominent slit-like spaces resembling vascular channels
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May be mistaken for vascular neoplasm, since SCL is also CD34 positive
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SCL is CD31 negative, unlike tumors with true endothelial differentiation
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