Dermatofibrosarcoma Protuberans
Definition
- Superficial infiltrative soft tissue neoplasm composed of bland spindle cells with a regular storiform pattern
Alternate / Historical Names
- DFSP
Diagnostic Criteria
- Cellular lesion composed of uniform small elongate cells
- Scant cytoplasm
- Cytologically bland, lacking pleomorphism
- Mitotic rate usually <5/10 hpf
- No atypical mitotic figures
- Uniform storiform pattern
- May be absent in early, plaque-like lesions
- Infiltrates between and around fat cells and adnexa
- Produces “string of pearls” or “honeycomb” or “lace-like” patterns
- This is one of the most useful histologic features
- Located in dermis and subcutaneous tissue
- Inconspicuous vasculature
- Scant collagenous stroma
- Giant cells and foam cells almost always absent
- CD34 extensively positive in nearly all cases
- May have myxoid areas
- May predominate resulting in a hypocellular lesion
- May obscure storiform pattern
- Diagnosis in such cases made from typical fat infiltration pattern in other areas and CD34 staining
- Myoid whorls occasionally seen
- Small collections of actin positive cells with abundant cytoplasm
- May be centered on vessels
- Very rare/unusual findings; if present, alternative diagnoses should be considered
- Giant cells
- Xanthoma cells
- Hemosiderin
- Inflammatory cells
- Rare cases may contain areas with fibrosarcomatous features
- Cellular plump spindled cells
- Uniform high grade cytologic atypia
- Frequent mitotic figures >5/10 hpf
- Herringbone pattern of fascicles
- Must make up at least 5-10% of the tumor or more than two low power fields
- Occurs in primary lesions as well as recurrences
- Clinical significance unclear
- If widely resected, metastasis is rare
- Very rare cases with appearance of MFH reported
- Clinical significance unclear
- Giant cell fibroblastoma is a closely related lesion
- More common in pediatric age group
- Mixtures may be seen
- Recurrences may be of the other neoplasm
- Same t(17;22) translocation
- Bednar tumor is a pigmented DFSP
- Contains elongate, bipolar heavily pigmented melanocytes
- Melanocytes S100 positive, HMB45 negative
- Remainder of tumor is negative
- More numerous in deep portions of tumor
- More common in black patients
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting: August 10, 2008
