What is the likely diagnosis and recommended management for a painful chest lesion with red borders and yellow‑brown crust one month after skin cancer excision?

Likely Diagnosis: Surgical Site Infection (SSI)

This painful chest lesion with red borders and yellow-brown crust one month post-excision most likely represents a surgical site infection, and the primary treatment is to open the incision, evacuate infected material, and perform dressing changes until healing by secondary intention occurs. 1

Clinical Assessment

The presentation of red borders with yellow-brown crust and pain at one month post-surgery is consistent with a superficial incisional SSI. Key distinguishing features to evaluate:

• Timing: SSIs rarely occur in the first 48 hours; infections after this period are more likely to be true SSIs 1
• Purulent drainage: The yellow-brown crust suggests purulent material
• Local inflammation: Red borders indicate erythema extending from the wound
• Pain: A cardinal feature of infection

Critical Differential Diagnoses to Exclude

While SSI is most likely, you must actively rule out:

1. Pyoderma gangrenosum (PG): Presents with painful, sterile ulcerations with characteristic bullae and pustules. This is a critical diagnosis because surgical debridement worsens PG (pathergy phenomenon). PG typically shows high fever, severe pain disproportionate to wound appearance, and rapid progression despite antibiotics 2, 3. If suspected, obtain biopsy showing neutrophilic infiltrate without infection/vasculitis and start immunosuppressive therapy (prednisolone 30 mg/day) 2

2. Recurrent/residual malignancy: Though less likely at one month, examine for rapidly growing nodules which could represent eruptive post-operative squamous cell carcinoma (mean appearance ~6 weeks) 4

Treatment Algorithm

Step 1: Determine Infection Severity

Minimal systemic signs (temperature <38.5°C, WBC <12,000 cells/µL, pulse <100 bpm, erythema <5 cm):

• Open the suture line
• Evacuate infected material
• Continue dressing changes until secondary intention healing
• No antibiotics needed 1

Significant systemic signs (temperature >38.5°C, heart rate >110 bpm, or erythema >5 cm beyond wound margins):

• Open the suture line
• Evacuate infected material
• Add 24-48 hours of antibiotics (empiric coverage based on surgical site—chest wall typically requires anti-staphylococcal coverage)
• Continue dressing changes 1

Step 2: Wound Management

• Perform Gram stain and culture of wound contents to guide antibiotic selection if needed
• Daily dressing changes
• Monitor for healing by secondary intention
• Do not perform incision and drainage under the assumption of simple abscess without considering PG if clinical features are atypical

Common Pitfalls

1. Over-prescribing antibiotics: Most superficial SSIs require only incision and drainage without antibiotics 1

2. Missing pyoderma gangrenosum: Surgical debridement of PG causes catastrophic worsening due to pathergy. If the patient has disproportionate pain, rapid progression despite antibiotics, or systemic symptoms (high fever), stop and biopsy before further surgical intervention 2, 3

3. Inadequate wound opening: The entire infected portion must be opened and drained—partial opening leads to treatment failure

4. Prophylactic antibiotics for drainage: These provide no benefit and are not recommended 1

Follow-up Monitoring

• Reassess wound in 48-72 hours
• If no improvement or worsening despite appropriate drainage, reconsider diagnosis (PG, recurrent malignancy)
• Complete healing typically occurs within 2-4 weeks with proper drainage and wound care
• If wound fails to heal after 8 weeks, consider biopsy to exclude malignancy or other pathology 5