Epidermal Cyst

Aka: Epidermal Cyst, Epidermoid Cyst, Epidermal Inclusion Cyst, Sebaceous Cyst, Epithelial Cyst, Keratin Cyst

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II. Epidemiology

  1. Most common skin cyst

III. Causes

  1. Ruptured Pilosebaceous Follicle (acne comedone)
  2. Local Trauma buries surface epithelium under skin

IV. Pathophysiology

  1. Previously known as Sebaceous Cysts but not derived from sebaceous tissue
  2. Common Locations
    1. Head and Neck
    2. Face
    3. Ears
    4. Chest
    5. Back
  3. Lesion
    1. Implanted epidermal elements into deeper dermal layers
    2. Cyst wall: stratified squamous epithelium
    3. Central punctum is typically present on close exam (hallmark finding of Sebaceous Cyst)
    4. Cyst contents
      1. Does not contain Sebaceous Glands
      2. Keratin and lipid
      3. Breakdown products
      4. Bacterial Infection
  4. Cyst rupture effect (keratin spills into Dermis)
    1. Significant inflammation
    2. Lesion may scar or become infected

V. Symptoms

  1. Usually asymptomatic
  2. Soft, yellow keratin discharge may have foul odor

VI. Signs

  1. Round, mobile, smooth surfaced, discrete Nodule
  2. Slow growing lesion from 5 mm to 5 cm in diameter
  3. Visible pore may be present at center of lesions
  4. May be inflamed if cyst has ruptured

VII. Differential Diagnosis

  1. See Soft Tissue Mass
  2. See site specific (e.g. Neck Masses in Children)
  3. Lipoma
  4. Milia (1-2 mm lesion)
    1. Puncture with needle, express with comedone extractor
  5. Dermoid cyst
    1. May extend intracranially (CT Head before excision)
    2. Locations
      1. Follow Cleavage Lines
      2. Sublingual
      3. Periorbital
      4. Base of nose
  6. Gardner's Syndrome
    1. Autosomal Dominant condition associated with Colonic Polyps and Colon Cancer
    2. Children with Sebaceous Cysts
    3. Adults with Sebaceous Cysts in rare location (fingers, toes)
    4. Multiple Lipomas, fibromas, osteomas

VIII. Types: Variations with multiple lesions

  1. Steatocystoma Multiplex
    1. Numerous 2-3mm lesions on trunk, arm, axilla, thigh
  2. Favre-Racouchot Syndrome
    1. Multiple facial lesions due to sun damage

IX. Management

  1. Non-inflamed cyst
    1. Small to moderate sized cysts
      1. See Minimal Epidermal Cyst Excision
    2. Large Cysts (2 cm or larger)
      1. Complete excision in standard fashion
      2. Remove cyst intact via Blunt Dissection
  2. Inflamed or infected cyst
    1. Warm compresses
    2. Incision and Drainage

X. Complications

  1. Cyst rupture
  2. Cyst inflammation or infection

XI. References

  1. Habif (1996) Clinical Dermatology, p. 644
  2. White (1994) Regional Dermatology, p. 27
  3. Higgins (2015) Am Fam Physician 92(7): 601-7 [PubMed]
  4. Zuber (2002) Am Fam Physician 65(7):1409-12 [PubMed]

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