Spindle Cell Lipoma
Definition
- Predominantly subcutaneous lesion composed of mature fat and bland spindle cells
Diagnostic Criteria
- If subcutaneous, must be located in posterior neck, upper back and shoulders
- Well circumscribed in these locations
- If located in other sites, must be restricted to dermis or submucosa
- Most reported in thigh, groin, buttock, face, hands, oral
- Less frequently encapsulated
- Variable amount of adult fat
- 10-90% of lesion
- Rare lesions lacking fat have been reported (see below)
- No lipoblasts
- 10-90% of lesion
- Small bland spindle cells with scant cytoplasm
- Elongate nuclei
- Mitotic figures absent
- Spindle cells arranged in short parallel arrays
- "School of fish"
- Nuclei may palisade
- Bundles of dense ropey collagen
- Stroma may be myxoid
- Vessels may be prominent, arborizing, thick walled
- Cartilaginous and osseous metaplasia reported in one case
- CD34 positive, usually extensive
- Mast cells may be numerous
- Variants may have distinctive patterns
- Vascular spindle cell lipoma
- Branching dilated or cleft like-spaces
- Papillary projections of tumor cells into the spaces
- Spaces usually cell free
- Spaces lined by endothelial cells with lymphatic phenotype
- D2-40 positive, CD31 focal or negative
- Previously termed pseudovascular spindle cell lipoma
- Based on studies without D2-40
- Recognized based on location, areas of typical spindle cell lipoma patterns and CD34 positvity
- Branching dilated or cleft like-spaces
- Fibrous spindle cell lipoma
- Abundant fibrous stroma
- Bundles of collagen
- EVG negative
- Recognized based on location, areas of typical spindle cell lipoma patterns and CD34 positvity
- Fat free (or almost free)
- May include above variant patterns
- May be predominantly myxoid
- Plexiform or curvilinear vasculature and vascular hyalinization may be prominent
- Recognized by location, CD34 reactivity and presence of areas with typical features of spindle cell lipoma
- Rare tumors combined with hibernoma have been reported
- No distinct clinical features
- Vascular spindle cell lipoma
- Frequent histologic overlap with pleomorphic lipoma
- Occasional to frequent cells with large atypical nuclei
- If pleomorphic features present, diagnosis is restricted to posterior neck, upper back and shoulders
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting : July 29, 2007
Updates: May 25, 2009; July 26, 2009
