Epidermal Inclusion Cyst of Vulva

An epidermal inclusion cyst of the vulva is a benign cyst lined by keratinising squamous epithelium and filled with keratin, formed when epidermis is implanted in the dermis after trauma, episiotomy, circumcision, surgery or blocked pilosebaceous follicles.

• It is a common vulval cyst.
• The cyst grows slowly and may rupture and become inflamed.
• Malignant change is very rare.

Slow-growing, firm, round, dome-shaped, mobile intradermal nodule 0.5 to 3 cm on the labia majora or minora, with a central punctum, and a yellow-white cheesy content.

• Usually painless; painful when inflamed, red, hot and tender.
• Differential diagnosis: Bartholin cyst, sebaceous cyst, lipoma, vulval abscess, molluscum contagiosum, skin tag, lymphangioma, vulval carcinoma.
• Complications: rupture with foreign body reaction, secondary infection, abscess, recurrence if the wall is left behind, rarely malignant transformation.

Diagnosis is clinical, with histology after excision.

• Clinical diagnosis by the punctum and cheesy discharge.
• Ultrasound if the nodule is deep or atypical.
• Excision with histology of the cyst wall.
• Swab for culture when inflamed with pus.
• Biopsy for any irregular, ulcerated or pigmented lesion.

Excise the whole cyst, including its wall, once any infection has settled.

• Supportive: reassure; avoid squeezing; keep the area clean; warm compresses for 10 minutes, 3 times daily when inflamed.
• Pharmacological: asymptomatic cyst needs no drug. Infected cyst: flucloxacillin 500 mg oral 6-hourly for 5 to 7 days (child 12.5 to 25 mg/kg 6-hourly, maximum 500 mg per dose). Penicillin allergy: clindamycin 300 mg oral 8-hourly for 5 to 7 days. Analgesia with paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours). A sterile, inflamed, non-infected cyst may be injected with triamcinolone 10 mg/mL, 0.1 to 0.2 mL intralesional (maximum 20 mg per session).
• Procedures: complete excision of the cyst with its wall under 1 percent lignocaine (maximum 3 mg/kg, absolute maximum 200 mg plain), by an elliptical incision around the punctum, blunt dissection and closure with absorbable 4-0 sutures. Wait 4 to 6 weeks after an infection has resolved before excising. Incision and drainage for an abscess, with later excision.
• Special groups: in pregnancy defer elective excision until after delivery unless symptomatic or infected; in diabetes check glucose before surgery.
• Red flags: rapid growth, ulceration, bleeding, fixed or hard cyst, pigment change, fever with spreading erythema.
• Follow-up: review at 1 to 2 weeks for wound healing and histology; reassess at 3 months for recurrence.