Solitary Fibrous Tumor
Differential Diagnosis
| Hemangiopericytoma | Solitary Fibrous Tumor |
|---|---|
| Sheets of cells, usually no collagen separation | Bands of collagen separate cells |
| Staghorn vessels required | Staghorn vessels may be present |
| CD34 50% positive | CD34 >90% positive |
They have the same behavior and the same features are predictive of malignancy.
| Smooth Muscle Tumor | Solitary Fibrous Tumor |
|---|---|
| Spindled cytoplasm | Scant cytoplasm |
| Long fascicular growth pattern | No fascicles or short fascicles |
| Actin positive >95% | Actin rare and focal |
| Desmin variable | Desmin negative |
| CD34 variable, weak | CD34 >90% positive |
| Gastrointestinal Stromal Tumor | Solitary Fibrous Tumor |
| Spindled or epithelioid cytoplasm | Scant cytoplasm |
| Skeinoid fibers, if present are irregular, globular and have prominent retraction | Ropy collagen |
| Hemangiopericytoma-like vessels uncommon | HPC-like vessels common |
| CD117 (CKIT), DOG1 85-95% positive | CD117, DOG1 negative |
| Actin 30-50% positive | Actin rare and focal |
| Nerve Sheath Tumor | Solitary Fibrous Tumor |
|---|---|
| Frequent palisading | No palisading |
| S100 positive in benign tumors | S100 <10% |
| CD34 focal dendritic pattern | CD34 extensive |
| Deep Fibrous Histiocytoma | Solitary Fibrous Tumor |
|---|---|
| No bands of collagen separating cells | Bands of collagen separate cells |
| Predominantly storiform | Usually patternless |
| Histiocytic differentiation present | No histiocytic differentiation |
| Usually uniform celllularity | Alternating hypocellular and hypercellular areas |
| CD34 40% positive | CD34 >95% positive (negative result favors fibrous histiocytoma) |
