Lipoma

Variant: Sclerotic Lipoma / Fibroma-like Lipoma

Circumscribed subcutaneous nodule
- Occasional cases with entrapped nerve, eccrine glands or arrector pili muscle
Extensive sclerotic collagen bundles
- Ranges from highly sclerotic to myxo-collagenous
  - Generally haphazard but may be whorled or concentric
- Vessels range from inconspicuous to prominent
Spindled or stellate cells in sclerotic areas
- Hypocellular
- At most focal mild atypia
- Mitotic figures rare
- Bi- or multinucleated cells may be present
  - Rare cases with floret cells
Admixed mature fat cells
- Usually less than 10% of lesion
  - Range 5-50%
- May be more prominent at periphery

Sclerotic Fibroma / Storiform Fibroma	Sclerotic Lipoma
Prominently concentric lamellar collagen	Collagen infrequently lamellar
Factor XIIIa and CD34 positive	Factor XIIIa and CD34 negative to rare
May be associated with Cowden disease	Not associated with Cowden disease

Fibrolipoma	Sclerotic Lipoma
Focal fibrous tissue in a lipoma	Focal fat in a predominantly fibrous lesion
Various locations	Predominantly located on fingers

Desmoplastic Fibroblastoma	Sclerotic Lipoma
Fat is not intrinsic to tumor	Fat is intrinsic to lesion

Fibroma of Tendon Sheath	Sclerotic Lipoma
Lacks intrinsic fat	Fat intrinsic to lesion
Smooth muscle actin positive	Smooth muscle actin negative to rare

Both are common on the fingers

Superficial Acral Fibromyxoma	Sclerotic Lipoma
Noncircumscribed	Circumscribed
CD34 positive	CD34 negative to rare
Lacks intrinsic fat component	Fat is integral to lesion

Both are common on the fingers

Laskin WB, Fetsch JF, Michal M, Miettinen M. Sclerotic (fibroma-like) lipoma: a distinctive lipoma variant with a predilection for the distal extremities. Am J Dermatopathol. 2006 Aug;28(4):308-16.
Zelger BG, Zelger B, Steiner H, Rutten A. Sclerotic lipoma: lipomas simulating sclerotic fibroma. Histopathology. 1997 Aug;31(2):174-81.