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

Supplemental studies

Immunohistology

Genetic studies

t(17;22) with fusion of COL1A1 and PDGFB in all cases tested

Differential diagnosis

• Dermatofibroma / Dermal fibrous histiocytoma
• Myxoid nerve sheath tumor
• Myxoid liposarcoma
• Plexiform fibrohistiocytic tumor
• Desmoplastic melanoma
• Fibrosarcoma
  

Clinical

• Wide age range but most common 20-40 years of age
• Trunk most common, followed by proximal extremities and head and neck
  • Very rare cases of similar appearing tumors in deep tissues and retroperitoneum
    • Same clinical behavior
• Slow growth
• Early lesions are plaque-like
• Late lesions protuberant
• 10-20% recur if widely excised
  • Frequent, aggressive recurrences if not widely excised
• Metastases <5% if widely excised
• Cases with areas of sarcoma appear to have the same behavior as usual cases if widely excised

Bibliography

• Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
• Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 5th edition, 2008
• Goldblum JR, Reith JD, Weiss SW. Sarcomas arising in dermatofibrosarcoma protuberans: a reappraisal of biologic behavior in eighteen cases treated by wide local excision with extended clinical follow up. Am J Surg Pathol. 2000 Aug;24(8):1125-30.
• Mentzel T, Schärer L, Kazakov DV, Michal M. Myxoid dermatofibrosarcoma protuberans: clinicopathologic, immunohistochemical, and molecular analysis of eight cases. Am J Dermatopathol. 2007 Oct;29(5):443-8.
• Goldblum JR, Tuthill RJ. CD34 and factor-XIIIa immunoreactivity in dermatofibrosarcoma protuberans and dermatofibroma. Am J Dermatopathol. 1997 Apr;19(2):147-53.
• West RB, Harvell J, Linn SC, Liu CL, Prapong W, Hernandez-Boussard T, Montgomery K, Nielsen TO, Rubin BP, Patel R, Goldblum JR, Brown PO, van de Rijn M. Apo D in soft tissue tumors: a novel marker for dermatofibrosarcoma protuberans. Am J Surg Pathol. 2004 Aug;28(8):1063-9.
• Billings SD, Folpe AL. Cutaneous and subcutaneous fibrohistiocytic tumors of intermediate malignancy: an update. Am J Dermatopathol. 2004 Apr;26(2):141-55.