What is the appropriate management of an epidermoid cyst on the back, and can these cysts recur?

Management of Epidermoid Cysts

Primary Treatment Approach

Incision and drainage is the definitive treatment for inflamed epidermoid cysts, and antibiotics should only be added if systemic signs of infection are present. 1, 2

Surgical Technique

• Perform incision and drainage with thorough evacuation of all purulent material as the cornerstone of treatment for inflamed cysts 1, 2
• Probe the cavity aggressively to break up any loculations or septations—this critical technical step prevents treatment failure and recurrence 2, 3
• Cover the surgical site with a simple dry dressing after drainage; this approach is both effective and evidence-based 1, 2
• Do not pack the wound with gauze—packing causes more pain without improving healing outcomes compared to simple dry dressing 1, 2, 3

When to Add Antibiotics

Systemic antibiotics are unnecessary unless specific criteria indicating systemic inflammatory response are met: 1, 2

• Temperature >38°C or <36°C 1, 2
• Tachycardia >90 beats per minute 1, 2
• Tachypnea >24 breaths per minute 1, 2
• White blood cell count >12,000 or <4,000 cells/µL 1, 2
• Erythema extending >5 cm beyond the wound margins with induration 2
• Markedly impaired host defenses or immunocompromised state 1, 2

Antibiotic Selection (When Indicated)

• For methicillin-susceptible S. aureus: Use cephalexin 500 mg every 6 hours orally or cefazolin 1 g every 8 hours IV 2
• For suspected or confirmed MRSA: Use vancomycin 15-20 mg/kg every 8-12 hours IV, trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily orally, doxycycline 100 mg twice daily orally, or clindamycin 300-450 mg four times daily orally (if local resistance <10%) 2
• Duration: 5-7 days depending on clinical response 2

Diagnostic Testing

• Do not routinely perform Gram stain and culture of pus from inflamed epidermoid cysts 1, 2
• Reserve cultures for cases with systemic signs of infection, treatment failure, or immunocompromised patients 2

Understanding the Pathophysiology

Inflammation in epidermoid cysts typically occurs as a reaction to rupture of the cyst wall and extrusion of contents into the dermis, rather than as a primary infectious process. 4 This explains why antibiotics alone without drainage will fail—the problem is mechanical, not primarily infectious. 2, 3

Recurrence of Epidermoid Cysts

Can They Recur?

Yes, epidermoid cysts can recur, particularly when inadequate initial treatment is performed. 1, 2, 3

Common Causes of Recurrence

• Inadequate initial drainage with incomplete evacuation of purulent material 2, 3
• Failure to probe and break up loculations or septations within the cavity 2, 3
• Retained foreign material or cyst wall remnants at the same site 1, 2, 3
• Incomplete removal of the cyst wall during definitive excision 5

Expected Healing Timeline

• Most wounds should heal within 2-3 weeks with proper initial treatment 2, 3
• Persistent drainage beyond 2-3 weeks indicates inadequate initial treatment requiring re-evaluation and likely re-drainage 2, 3

Management of Recurrent or Persistent Drainage

If infection persists or drainage continues beyond 2-3 weeks: 2, 3

• Re-open the incision and ensure complete evacuation of all contents 2, 3
• Thoroughly probe the cavity again to break up any remaining loculations 2, 3
• Search for retained foreign material or incomplete cyst wall removal 1, 2, 3
• Consider complete excision of the cyst and its wall once acute inflammation has resolved to prevent future episodes 2, 6

Definitive Treatment to Prevent Recurrence

For patients with recurrent infections at the same site, complete surgical excision of the cyst with its intact wall is the definitive solution. 6, 7, 8, 5

• Timing matters: Postpone definitive excision until inflammation has completely subsided, as inflamed cysts are difficult to excise 8
• Delayed primary closure technique: One approach involves initial incision and drainage, followed 5-7 days later by complete excision of the cyst wall parallel to Langer's tension lines with delayed primary closure—this resulted in no recurrences in a case series 6
• Complete wall removal is essential: The cyst wall must be removed completely to avoid relapses 5
• Minimal excision technique: For uninflamed cysts, a 2-3 mm incision with expression of contents and extraction of the cyst wall is effective and does not require suture closure 8

Critical Pitfalls to Avoid

• Never prescribe antibiotics without addressing the mechanical problem—antibiotics alone without adequate drainage will fail 2, 3
• Never close the wound without adequate drainage—this leads to recurrent infection 2, 3
• Never assume ongoing drainage beyond 2-3 weeks is normal healing—this suggests inadequate initial treatment requiring re-drainage 2, 3
• Do not routinely prescribe antibiotics in the absence of systemic infection signs—this is unnecessary and promotes resistance 1, 2
• Avoid wound packing—it increases pain without benefit 1, 2, 3