BASICS
DESCRIPTION
- Correct nomenclature is "epidermoid cyst," as these structures have no sebaceous gland component (1).
- A benign, encapsulated, subepidermal nodule filled with keratinaceous material
- Most commonly located on face, neck, trunk
- Synonym(s): epidermal inclusion cysts; epidermal cysts; keratin cysts; inclusion cysts
EPIDEMIOLOGY
- Most common cutaneous cyst
- Predominant sex: male > female (2:1)
- Predominant age: most common in 3rd to 4th decades
- An estimated 1% of epidermoid cysts are found to have malignant transformation (2).
- Squamous cell carcinomas are the most common (70%), followed by basal cell carcinoma (10%).
ETIOLOGY AND PATHOPHYSIOLOGY
Often result from rupture or occlusion of pilosebaceous follicles resulting in the accumulation of keratin in the subepidermal or dermal layer of the skin
- Spontaneous
- Damage to hair follicle
- Ruptured sebaceous gland
- Congenital trauma (translocation of surface epithelial cells deep to the dermis) (3)
Genetics
Most cases are sporadic and nonfamilial. Epidermoid cysts are also noted in the following:
- Gardner syndrome (autosomal dominant)
- Consider when encountering epidermoid cysts unusual in number or location (multiple digits, for example) (4), especially if found in conjunction with osteomas.
- Other genetic syndromes with cystic structures resembling epidermoid cysts
- Gorlin syndrome (autosomal dominant)
- Pachyonychia congenita type II (autosomal dominant)
GENERAL PREVENTION
Avoid significant sun exposure.
DIAGNOSIS
HISTORY
- Mass slowly growing over time
- Recent trauma
- "Cheese-like" material expressed from cyst, often with a rancid odor
PHYSICAL EXAM
- Firm to fluctuant, often partially fixed to overlying epidermis, dome-shaped, flesh-to-yellow-colored
- Commonly located on face, neck, upper back, chest, and scrotum (3); if due to trauma, on buttocks, palms, or plantar side of feet
- Varying in size (few millimeters to 5 cm)
- Central dark comedone is often present (4).
- Signs of rupture or inflammation (erythema, tenderness, swelling) may be present.
DIFFERENTIAL DIAGNOSIS
- Trichilemmal cyst (pilar cyst)
- Lipoma
- Steatocystoma
- Branchial cleft cyst
- Dermoid cyst
- Fibrous tissue tumor
- Gardner syndrome
- Milia
- Myxoid cyst
- Favre-Racouchot syndrome
- Pilonidal cyst
DIAGNOSTIC TESTS & INTERPRETATION
Diagnosis is by clinical exam.
Diagnostic Procedures/Other
Need for histologic exam of excised mass is debatable.
Test Interpretation
- Stratified, squamous cyst wall
- Granular layer
- Eosinophilic keratinaceous debris
TREATMENT
Sebaceous cysts are generally benign and frequently no therapy is indicated. If removal is desired or indicated, every effort should be made to remove the entire cyst wall to prevent recurrence.
MEDICATION
An inflamed, but uninfected, epidermoid cyst may be injected with a corticosteroid help reduce inflammation but should still be followed by definitive removal (4).
ADDITIONAL THERAPIES
To minimize scarring, a carbon dioxide laser may be used to vaporize an epidermoid cyst on the face or other sensitive area (5).
SURGERY/OTHER PROCEDURES
- Indications
- Cosmesis
- Cyst inflammation (must wait until inflammation subsides) due to either rupture or infection
- Cyst location impairing patient's functioning
- Irregular appearance or texture concerning for underlying malignancy
- Three surgical options
- Punch biopsy excision appears to be superior to traditional wide elliptical excision for the treatment of sebaceous cysts when intervention is necessary; results in decreased scarring and faster healing time (6)[B]
- Minimal incision technique involves injection of anesthetic in a field block, making a 2- to 3-mm punch incision, kneading the lesion vigorously, and expressing the cyst contents through the incision. Following expulsion of the cyst contents, the loosened capsule is delivered through the small opening. Closure with suture is optional. A similar technique involves making a small linear incision over the top of the cyst, followed by vigorous squeezing around the circumference of the cyst to expel the cyst contents, and loosen the cyst wall. The wall may then be grasped and removed and suture or Steri-Strip closure is performed (6).
- Traditional wide excision, via an elliptical incision, is more time-consuming and results in more significant scarring; however, it has almost no risk of cyst recurrence if the cyst wall is entirely removed (6).
- A two-step approach has also been suggested for removal of uninfected sebaceous cysts by using a laser to create a small hole to remove the cyst contents. A follow-up visit is done 1 month later, and the cyst wall is removed entirely using a minimal excision technique. This method results in minimal scarring and is effective for large cysts or those located in areas of thick skin or cosmetic concern (5)[C].
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
- Uncomplicated sebaceous cysts do not require regular follow-up.
- Any recurrent cysts should be excised using a traditional elliptical incision.
- Solid or atypical masses noted in excision should be sent for histologic analysis.
PROGNOSIS
Overall recurrence rate after excision is <3% (less with elliptical incision vs. punch biopsy).
COMPLICATIONS
- Cyst inflammation can occur and is rarely indicative of infection. More often, inflammation is secondary to cyst wall rupture with leakage of cyst contents into the surrounding dermis, eliciting a brisk inflammatory response.
- Rupture of sebaceous cyst resulting in foreign body giant cell reaction
- Secondary polymicrobial infection
- Rare presence of underlying malignancy (squamous cell carcinoma, basal cell carcinoma) within the cyst wall, leading some to advocate for histologic analysis of all removed cyst walls (2)[C]
REFERENCES
11 Luba MC, Bangs SA, Mohler AM, et al. Common benign skin tumors. Am Fam Physician. 2003;67(4):729-738.22 Liau JL, Altamura D, Ratynska M, et al. Basal cell carcinoma arising from an epidermal cyst: When a cyst is not a cyst. Case Rep Dermatol. 2015;7(1):75-78.33 Zuber TJ. Minimal excision technique for epidermoid (sebaceous) cysts. Am Fam Physician. 2002;65(7):1409-1412.44 Higgins JC, Maher MH, Douglas MS. Diagnosing common benign skin tumors. Am Fam Physician. 2015;92(7):601-607.55 Wu H, Wang S, Wu L, et al. A new procedure for treating a sebaceous cyst: removal of the cyst content with a laser punch and the cyst wall with a minimal postponed excision. Aesthetic Plast Surg. 2009;33(4):597-599.66 Moore RB, Fagan EB, Hulkower S, et al. Clinical inquiries. What's the best treatment for sebaceous cysts? J Fam Pract. 2007;56(4):315-316.
ADDITIONAL READING
Lee HE, Yang CH, Chen CH, et al. Comparison of the surgical outcomes of punch incision and elliptical excision in treating epidermal inclusion cysts: a prospective, randomized study. Dermatol Surg. 2006;32(4):520-525.
CODES
ICD10
- L72.3 Sebaceous cyst
- L72.0 Epidermal cyst
ICD9
706.2 Sebaceous cyst
SNOMED
- epidermoid cyst of skin (disorder)
- epidermoid cyst of skin of face (disorder)
- Epidermoid cyst of skin of neck (disorder)
- Epidermoid cyst of skin of chest (disorder)
- Epidermoid cyst of skin of scrotum (disorder)
- Epidermoid cyst of skin of back (disorder)
CLINICAL PEARLS
- Sebaceous cysts are generally benign and do not warrant routine excision.
- Indications for cyst removal include cosmesis, inflammation, concern for underlying malignancy, and functional impairment.
- For removal of 1- to 2 cm uncomplicated cysts, a punch biopsy is superior to an elliptical incision with respect to quicker wound healing and less scarring.
- Must ensure that entire cyst wall has been removed to prevent recurrence.
- Solid or atypical masses noted in excision warrant histologic evaluation.