What is the difference in diagnosis and treatment between epidermoid and sebaceous cysts?

Differences Between Epidermoid and Sebaceous Cysts: Diagnosis and Treatment

Surgical excision is the definitive treatment for both epidermoid and sebaceous cysts, with complete removal of the cyst wall being essential to prevent recurrence. 1

Diagnostic Differences

Epidermoid Cysts

• Definition: Benign tumors derived from the infundibular portion of hair follicles with flattened surface epithelium and keratohyaline granules 2
• Clinical Features:
  • Dome-shaped, asymptomatic lesions 3
  • Presence of an epidermal punctum (central black dot) is a diagnostic hallmark 1
  • Most commonly found on face (65%), trunk (10.9%), scalp (7.9%), and neck (7.9%) 2
  • More common in men (59.5%) than women (40.5%) 2
  • Most frequent in adults in their 40s and 50s (17.6%) 2
• Imaging:
  • Ultrasound shows oval-shaped, hypoechoic lesions (91.5%) 4
  • "Pseudotestis" homogeneous appearance in about 50.8% of cases 4
  • Visualization of skin pore (epidermal punctum) on high-frequency ultrasound 4

Sebaceous Cysts

• Definition: Benign enveloped nodules resulting from obstruction of a hair follicle 4
• Clinical Features:
  • Similar in appearance to epidermoid cysts but contain sebaceous material
  • May have a more yellowish appearance due to sebaceous content
• Imaging:
  • Ultrasound appearance similar to epidermoid cysts 4
  • May show internal echoes representing sebaceous material

Treatment Approaches

Epidermoid Cysts

1. Minimal Excision Technique (preferred for uncomplicated cysts):

   • 2-3 mm incision
   • Expression of cyst contents through compression
   • Extraction of the cyst wall through the small incision
   • No suture closure required
   • Use gauze or splatter shield to protect from spraying contents 3

2. Complete Surgical Excision:

   • Required for larger or complicated cysts
   • Complete removal of cyst wall is essential to prevent recurrence 1
   • Can be performed under local anesthesia in most cases
   • Low complication rate of 2.2% 1

3. Management of Inflamed Cysts:

   • Postpone excision until inflammation has subsided 3
   • May require antibiotics or intralesional steroids to reduce inflammation

Sebaceous Cysts

• Treatment approach is similar to epidermoid cysts
• Complete surgical excision with removal of entire cyst wall

Special Considerations

Complicated Cysts

• For cysts that increase in size, biopsy is recommended 5
• For cysts that resolve after aspiration but contain bloody fluid:
  • Place a tissue marker
  • Perform cytologic evaluation of fluid
  • Follow up with percutaneous vacuum-assisted biopsy or excision if positive findings 5

Malignant Transformation

• Although rare, epidermoid cysts can undergo malignant transformation into squamous cell carcinoma 6
• Risk factors for malignant transformation:
  • Long-standing cysts
  • Cysts with recent rapid growth
  • Ulceration or bleeding
• All surgically excised cysts should undergo pathologic evaluation when:
  • Unusual clinical features are present
  • There is clinical suspicion of malignancy 6, 3

Follow-up Recommendations

• For benign cysts with complete excision: no specific follow-up needed
• For recurrent masses: tissue biopsy is recommended 5
• For cysts with negative cytology but bloody fluid: physical examination with or without ultrasound/mammogram every 6-12 months for 1-2 years 5

Pitfalls to Avoid

1. Incomplete removal of the cyst wall leading to recurrence
2. Attempting excision during active inflammation
3. Failing to recognize signs of potential malignancy
4. Not using protective barriers during cyst expression, risking splatter of contents
5. Overlooking the need for histopathological confirmation in suspicious cases

By understanding these key differences in diagnosis and treatment approaches, clinicians can effectively manage both epidermoid and sebaceous cysts while minimizing complications and recurrence rates.