Pleomorphic Lipoma
Differential Diagnosis
- Spindle cell lipoma
- Atypical lipomatous tumor
- Fat necrosis
- Pleomorphic hyalinizing angiectatic tumor
Spindle Cell Lipoma vs. Pleomorphic Lipoma
- We consider these to be part of a spectrum
- Mixtures are common
- If atypical cells are present, location becomes definitional
- Restricted to posterior neck, upper back, shoulders
Pleomorphic Lipoma vs Atypical Lipomatous Tumor
- The diagnosis of tumors composed of mature fat with atypia depends upon the location
- In the dermis and subcutis of the posterior neck, upper back or shoulders, it is considered pleomorphic lipoma
- In all other locations, it is considered atypical lipomatous tumor
- Pleomorphic lipoma MDM2 and CDK4 negative, while most ALT are positive
- Ropey collagen and extensive CD34 staining support pleomorphic lipoma
| Pleomorphic Lipoma | Fat Necrosis |
|---|---|
| At least scattered large eccentric nuclei | Small central nuclei |
| No prominent foamy cell population | Foamy cells frequently fill spaces of dead adipocytes |
| Ropy collagen | No ropy collagen |
| Restricted to back of neck, upper back and shoulders | Various locations |
| Pleomorphic Lipoma | Pleomorphic Hyalinizing Angiectatic Tumor |
|---|---|
| No intracytoplasmic hemosiderin | Intracytoplasmic hemosiderin |
| No aggregates of large vessels | Aggregates of vessels with hyalinized walls and fibrin |
| Ropy collagen | No ropy collagen |
| Restricted to back of neck, upper back and shoulders | Various locations |
