Spindle Cell Lipoma
Differential Diagnosis
- Pleomorphic lipoma
- Mature fat with admixed other components
- Predominantly spindled
- Predominantly myxoid
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
| Spindle Cell Lipoma |
Angiolipoma |
| Predominantly back of neck, upper back, shoulders |
Very rare on neck, upper back |
| Usually solitary |
Frequently multiple |
| CD34 positive |
CD34 stains only endothelium and scattered cells |
| Prominent spindle cell component |
Prominent vascularity |
| No fibrin thrombi |
Frequent fibrin thrombi |
| May contain pleomorphic cells (admixed pleomorphic lipoma) |
No pleomorphic cells |
Both contain spindle cell and adipose components and both are CD34 positive in the spindled component
| Spindle Cell Lipoma |
Fibrolipoma |
| Predominantly back of neck, upper back, shoulders |
Various locations |
| Prominent spindle cell component |
Lacks prominent spindle cells |
| CD34 positive |
CD34 negative |
| Ropy bundles of collagen |
Lacks ropy collagen |
| Spindle Cell Lipoma |
Fibrolipomatous Hamartoma of Nerve |
| Predominantly back of neck, upper back, shoulders |
Usually involves median nerve |
| Does not involve nerves |
Infiltrates and surrounds large nerve |
| Usually age 40-70 |
Presents under age 30 |
| No neural symptoms |
Neural symptoms |
| Spindle Cell Lipoma |
Myolipoma |
| Restricted to back of neck, upper back, shoulders |
Predominantly pelvic |
| Scant cytoplasm |
Tapered cytoplasm in spindle cells |
| CD34 positive |
CD34 negative |
| Actin negative |
Actin positive |
| Spindle Cell Lipoma |
Spindle Cell Variant Atypical Lipomatous Tumor |
| Restricted to back of neck, upper back, shoulders |
Various locations |
| Bland spindle cells |
Mild to moderate atypia of spindle cells |
| Ropy collagen bundles |
No ropy collagen |
| Circumscribed |
May be infiltrative |
| Uniformly strong CD34 |
CD34 only occasionally reactive |
| MDM2 0-12% and CDK4 0-6% |
MDM2 and CDK4 most positive |
| No areas of usual ALT pattern |
Areas of usual ALT pattern |
MDM2 and CDK4 figures given for usual ALT as no data for spindle cell variant
| Spindle Cell Lipoma |
Schwannoma or Neurofibroma |
| S100 negative except for mature fat |
S100 positive |
| Uniformly strong CD34 |
CD34 only scattered small spindle cells |
| Spindle Cell Lipoma |
Solitary Fibrous Tumor |
| Fat is integral part of lesion |
Fat only at infiltrative border |
| May contain pleomorphic cells if admixed with pleomorphic lipoma |
No large pleomorphic cells |
| Ropey collagen bundles |
Finely dispersed collagen |
| Lacks staghorn vessels |
Frequent staghorn vessels |
| Myxoid Liposarcoma |
Spindle Cell Lipoma with Myxoid Stroma |
| Infrequent prominent spindle cell component |
Prominent spindle cell component |
| Prominent "chicken wire" vascular pattern |
Lacks "chicken wire" vascular pattern |
| No dense collagen bundles |
Dense collagen bundles |
| Very rare in subcutis or dermis |
Usually in subcutis or dermis |
| CD34 negative or scattered small cells |
CD34 widely positive |
| t(12;16) or t(12;22) |
Frequent abnormalities of chromosomes 13 or 16 |
| Myxolipoma |
Spindle Cell Lipoma with Myxoid Stroma |
| Lacks prominent spindle cell component |
Prominent spindle cell component |
| May have prominent vascularity |
Vascularity rarely prominent |
| No dense collagen bundles |
Dense ropy collagen bundles |
| Location variable |
Largely restricted to back, shoulders, posterior neck |
| Spindle Cell Lipoma, Myxoid Predominant |
Superficial Angiomyxoma |
| Usually has areas of typical spindle cell lipoma |
Lacks areas of typical spindle cell lipoma |
| Parallel arrays of spindle cells in areas |
Randomly arranged cells |
| Ropey collagen bundles |
Lacks ropey collagen |
| Lacks neutrophils or entrapped adnexae |
Frequent neutrophils and entrapped adnexae |
