What is the best course of treatment for a sacral wound with dermal fibrosis and telangiectasia, rebiopsied showing dermal fibrosis and CD34 negativity?

Sacral Wound with Dermal Fibrosis, Telangiectasia, and CD34 Negativity

This sacral wound requires immediate rebiopsy with deep tissue sampling to definitively rule out dermatofibrosarcoma protuberans (DFSP) with fibrosarcomatous transformation, as CD34 negativity in the context of dermal fibrosis is a critical red flag for malignant transformation that demands urgent multidisciplinary evaluation. 1

Critical Diagnostic Considerations

Why CD34 Negativity Matters

• CD34 negativity in a fibrotic sacral wound is highly concerning for fibrosarcomatous DFSP (FS-DFSP), which is characterized by loss of CD34 immunostaining, higher cellularity, cytologic atypia, and mitotic activity >5/10 high-power fields 1
• Standard DFSP typically shows positive CD34 staining in 90% of cases, making CD34 negativity an atypical finding that warrants aggressive diagnostic workup 1
• FS-DFSP carries significantly higher metastasis risk compared to conventional DFSP and requires referral to a sarcoma center 1

Immediate Rebiopsy Protocol

• Obtain a deep subcutaneous punch biopsy or incisional biopsy extending into subcutaneous tissue, as superficial biopsies frequently miss DFSP 1
• Request specific immunohistochemical staining panel: CD34, factor XIIIa, S100 (to exclude other spindle cell tumors when CD34 is negative), nestin, apolipoprotein D, and cathepsin K 1
• Order FISH, PCR, or conventional cytogenetics to detect the hallmark t(17;22)(q22;q13) translocation (COL1A1::PDGFβ fusion gene), which is present in >90% of DFSP cases 1
• Ensure evaluation by a qualified sarcoma or dermatopathologist if available, as DFSP is frequently misdiagnosed even with multiple biopsies 1

Differential Diagnosis Framework

Malignant Processes to Exclude

• Fibrosarcomatous DFSP: CD34 negative, herringbone pattern replacing storiform pattern, increased mitotic activity, cytologic atypia 1
• Cutaneous squamous cell carcinoma: Can present as non-healing sacral wound with dermal fibrosis 2
• Other soft tissue sarcomas: Require S100 negativity to differentiate from neural tumors when CD34 is absent 1

Benign Considerations (Less Likely Given CD34 Negativity)

• Radiation-induced fibrosis: Would show telangiectasia but typically maintains some CD34 positivity in vessels 2
• Chronic pressure ulcer with fibrosis: Should not show organized storiform or fascicular pattern 1

Management Algorithm Pending Definitive Diagnosis

Wound Care During Evaluation

• Irrigate with sterile saline to remove debris without causing additional tissue damage 2
• Apply non-adherent dressing (not hydrocolloid or foam) to protect wound while allowing drainage and preventing adherence that could disrupt tissue for repeat biopsy 2, 3
• Change dressings every 5-7 days unless signs of infection develop 2, 3
• Do NOT debride aggressively until malignancy is definitively excluded, as this could spread tumor cells or remove diagnostic tissue 2, 3

Infection Surveillance

• Monitor for clinical signs of infection: increased pain, erythema, purulent exudate, odor, wound dehiscence, or systemic signs 1, 2
• Obtain wound cultures only if infection is suspected, using tissue biopsy or curettage from wound base rather than swabs 1, 2
• Do NOT treat with antibiotics prophylactically in absence of clinical infection 2

If DFSP is Confirmed

Surgical Management (First-Line Treatment)

• Mohs micrographic surgery or complete circumferential peripheral deep-margin assessment (CCPDMA/PDEMA) is the preferred surgical approach, as DFSP has irregular finger-like extensions requiring meticulous margin control 1
• When Mohs/PDEMA is unavailable, perform wide excision with 2-4 cm margins extending to investing fascia, with complete histologic margin verification 1
• Delay reconstruction with extensive undermining until negative margins are confirmed histologically 1
• Consider split-thickness skin grafting rather than complex flaps to facilitate monitoring for recurrence 1
• Sacral location has favorable prognosis: lower recurrence rates (0-60% historically, 7.3% with modern wide margins) compared to ischial ulcers 1, 4

If Unresectable or Positive Margins

• Confirm t(17;22) translocation via FISH before initiating targeted therapy 1
• Imatinib mesylate (tyrosine kinase inhibitor) is FDA-approved for unresectable, recurrent, or metastatic DFSP in adults with confirmed PDGFβ translocation 1
• Radiation therapy (5,000-6,000 cGy in 200-cGy fractions) for close-to-positive or positive margins when re-resection is not feasible, with fields extending 3-5 cm beyond surgical margin 1

If Fibrosarcomatous Transformation Confirmed

• Immediate multidisciplinary consultation with sarcoma team is mandatory 1
• Refer to NCCN Soft Tissue Sarcoma Guidelines for multimodal therapy including consideration of CT chest and draining nodal basin imaging 1
• FS-DFSP requires more aggressive surveillance due to higher metastasis risk 1

Critical Pitfalls to Avoid

• Do NOT assume this is a simple pressure ulcer despite sacral location—the combination of dermal fibrosis, telangiectasia, and CD34 negativity is atypical for benign pressure injury 1, 2
• Do NOT proceed with surgical flap reconstruction before obtaining definitive pathologic diagnosis, as this could complicate subsequent cancer surgery 1
• Do NOT rely on single negative biopsy if clinical suspicion remains high—DFSP is frequently misdiagnosed on initial biopsy 1
• Do NOT stage as pressure ulcer if malignancy suspected—this delays appropriate oncologic management 4

Follow-Up Protocol

• Clinical examination of primary site every 6-12 months for minimum 5 years after treatment, as local recurrence is the primary concern 1
• Rebiopsy any suspicious areas immediately during surveillance 1
• Patient education regarding self-examination for new nodules or non-healing areas 1