- Benign tumor most commonly presenting on the posterior aspect of the neck, shoulders or upper back
- Most common in older males
- Presents as a well-circumscribed, slowly growing subcutaneous, or rarely dermal, mass
- Admixture of mature adipose tissue and uniform spindle cells with pale eosinophilic cytoplasm
- Variable amounts of hyalinized collagen and occasional giant cells
- Lipoblasts are rarely present.
- Variable vascularity, sometimes with a focal hemangiopericytoma-like pattern
- Numerous mast cells are typically present.
- The spindle cells are positive for CD34 and negative for S-100.