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