Updated: 8/12/2019

Dermatofibrosarcoma Protuberans

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Introduction
  • Overview
    • dermatofibrosarcoma protuberans is a rare low-grade fibrogenic cutaneous sarcoma that occurs in early to midadult life
      • variants include
        • Bednar tumor
          • pigmented variant that is 7.5x more common in African Americans
        • fibrosarcomatous
          • more aggressive variant with poor prognosis
  • Epidemiology
    • incidence
      • accounts for 1% of soft tissue sarcomas
    • demographics
      • slightly more common in males 
      • usually presents in people aged 20-50 years old
      • more common in African Americans (2:1) vs. Caucasians
    • location
      • trunk > proximal extremities > head/neck
  • Genetics
    • mutations
      • associated with t(17;22)
        • encodes for PDGF-beta chain (PDGFB)/collagen type I alpha 1 (COL1A1) fusion protein
  • Prognosis
    • local recurrence is common
    • distant metastasis is rare (< 5%)
      • lung is the most common site of distant metastasis
      • occurs via hematogenous spread
      • usually preceded by multiple local recurrences
    • worse prognosis seen with
      • regional lymph node involvement
      • fibrosarcomatous progression DFSP variant
      • histologic features: high number of mitotic figures, increased cellularity, DNA aneuploidy, TP53 gene overexpression, and the presence of fibrosarcomatous changes
      • age > 50 years old
Symptoms
  • Presentation
    • usually an slowly enlarging painless mass
      • composed of firm irregular nodules
      • may have dark red or blue discoloration
Imaging
  • Radiographs
    • views
      • CXR
    • indications
      • screen for pulmonary metastasis in high-risk cases (i.e. recurrence or suspicion for a fibrosarcoma variant of DFSP)
  • CT
    • indications
      • suspected direct bone involvement or metastasis
  • MRI
    • indications
      • preoperative assessment in larger or atypical lesions and recurrent disease
  • Ultrasound
    • indications
      • monitoring of local DFSP or regional lymph node metastasis
  • PET
    • indications
      • monitoring of metastatic disease
Histology
  • Biopsy is required for diagnosis
  • Histology
    • classically appears as uniform fibroblasts arranged in storiform pattern around an inconspicuous vasculature
    • Bednar variant has scattered melanin-containing dendritic cells
    • fibrosarcomatous variant has a characteristic herringbone pattern
Treatment
  • Nonoperative
    • imatinib
      • inhibits PDGF-receptor tyrosine kinase
      • indications
        • adult patients with unresectable, recurrent, and/or metastatic DFSP
      • outcomes
        • 65% response rate
        • no response in patients who lack the t(17,22) mutation
  • Operative
    • wide surgical resection +/- adjuvant radiation therapy
      • indications
        • patients with resectable DFSP
        • adjuvant radiation therapy is useful in patients with positive margins or in whom adequate wide excision alone may result in major cosmetic or functional deficits
      • technique
        • clean margins are an important goal of surgical resection
          • obtain 2-3cm margins
          • dissect deep to and excise all tissue including the fascia
        • total dose of radiation therapy is 50-70 Gy
      • outcomes
        • 15.7% recurrence for lesions on the body
        • 51.8% recurrence rate for lesions on the head/neck
Ibank
  Location
Xray
Xray
CT
B. Scan
MRI
MRI
Histo(1)

Case A

tibia
 
 
 
(1) - histology does not always correspond to case 


QBANK
 
 

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