Dermatofibrosarcoma

Disease Description (Causes and Symptoms)

• Definition: Dermatofibrosarcoma protuberans (DFSP) is a low- to intermediate-grade malignant cutaneous soft-tissue tumor arising in the dermis and subcutaneous tissue. It has a high tendency for local invasion and recurrence, while metastasis is rare. Some cases progress to high-grade fibrosarcoma (fibrosarcomatous variant), increasing the risk of metastasis.
• Causes and pathophysiology: A COL1A1–PDGFB gene fusion (t(17;22)) is identified in most cases, and activation of the PDGFB pathway is involved in tumor growth. It is not a familial hereditary disease, and some cases have been reported to be associated with trauma or scars (surgical or burn scars) at the tumor site. Histologically, it often shows a storiform pattern and is frequently CD34-positive.
• Main symptoms: A slowly growing, skin-colored, firm plaque or reddish-brown nodule (usually in the trunk, extremities, and head and neck, in that order). It is usually confined to the surface, and its size is generally ≤5 cm, but with recurrence or progression it may invade deep tissues or become adherent. Pain is rare, and diagnosis is often delayed because there are no symptoms.

Treatment Methods (Latest Standards, Medications, Procedures/Surgery, and Lifestyle Management) and Precautions for This Disease

• Standard treatment
  • Surgical excision: Complete excision is the first-line treatment. For wide local excision, the general recommendation for the margin is at least 2–3 cm depending on the characteristics of the skin and tissue (including the fascia below), but the decision is made considering the location, function, and cosmetic outcome. Performing a sufficiently wide excision during the first surgery is important for reducing recurrence.
  • Mohs micrographic surgery (Mohs): This is widely used, particularly for the head and neck or areas where preservation of function and cosmetic appearance is important, because it preserves tissue and reduces the local recurrence rate.
• Adjuvant and systemic treatment
  • Radiation therapy: Used as adjuvant therapy for unresectable disease, residual tumor (when negative margins cannot be achieved), or recurrent lesions. When resection is not possible, it may also be used to reduce tumor size.
  • Targeted therapy (tyrosine kinase inhibitors): For unresectable or metastatic DFSP with a confirmed COL1A1–PDGFB fusion, PDGFR-targeting drugs such as imatinib may be effective and are considered standard options in some cases. The effectiveness of systemic chemotherapy is limited.
  • Investigational approaches: Various studies are ongoing, including research on drugs targeting the PDGF pathway.
• Lifestyle management and precautions
  • Consult the treating medical team about postoperative wound care (infection prevention and scar management) and reconstruction (plastic and functional reconstruction when necessary).
  • Because complete excision during the first surgery is very important, consider this when planning surgery and selecting a specialist.
  • Long-term follow-up after surgery is necessary, given the tumor’s characteristic of growing slowly.
• Risk of complications
  • Local recurrence (high); when recurrence occurs, deeper invasion and the possibility of metastasis increase. Functional and cosmetic defects caused by surgery, side effects of radiation, and adverse effects of targeted therapy (e.g., gastrointestinal symptoms and edema from imatinib).

Checkpoints Before an Outpatient Visit (Including What to Bring, Preparing for the Appointment, and Example Questions)

• Items to bring
  • A list of currently used medications (including prescription drugs, nonprescription drugs, and supplements)
  • Previous medical certificates, surgical records, and pathology reports (if available, biopsy results or pathology slides/reports)
  • Results of previous imaging tests (images, MRI/CT/chest X-ray, etc.)
  • The lesion’s growth history (records of changes over time using photographs)
  • Records of any previous wounds, trauma, surgery, or scars
• Information to organize before the appointment
  • When the lesion was first noticed and how quickly it has changed
  • Whether there is pain, bleeding, color change, or change upon contact
  • Whether the same area has previously undergone excision or treatment
• Information to tell the doctor first during the outpatient visit
  • Whether there has been a rapid change in size, onset of pain, ulceration, or bleeding
• Example questions (for use during the appointment)
  • “What findings are important in the pathology results I brought?”
  • “What will the expected extent of excision and reconstruction method be during surgery?”

Examples of General Questions to Ask the Doctor

• “Why was my lesion definitively diagnosed as DFSP (what are the pathological findings)? What are the results of the CD34 or gene fusion tests?”
• “Can surgery cure it? Which surgical method do you recommend (wide local excision vs. Mohs), and why?”
• “How much of a surgical margin is needed? How much does the recurrence rate increase if sufficient excision is not achieved during the first surgery?”
• “When is radiation therapy or drug treatment (imatinib) needed? What are the side effects?”
• “How should follow-up examinations be conducted after surgery (frequency and duration)?”

Examples of Disease-Specific Questions

• “Was a COL1A1–PDGFB gene fusion test performed or should one be performed for my lesion? How would treatment differ depending on the result?”
• “Because of the location of my lesion (e.g., the face or head and neck), wide excision is difficult. Which option would be appropriate: Mohs surgery or adjuvant radiation therapy? What are the options for reconstruction after surgery (flap or graft)?”