A sebaceous cyst (epidermoid cyst or wen) is a retention cyst produced by obstruction to the mouth of a sebaceous gland. Therefore, sebaceous cysts may occur wherever sebaceous glands exist and are not found on the gland – free palms and soles. They are especially common on the scalp, face, scrotum and vulva and on the lobe of the ear. The cyst is fluctuant and cannot be moved separately from the overlying skin. There may be a typical central punctum and the contents are cheesy with an unpleasant smell. The lining membrane consists of squamous epithelium.
- Ulceration, which may then resemble a fungating carcinoma (‘Cock’s peculiar tumour’ ).
- Calcifi cation, producing a hard subcutaneous tumour misnamed a ‘benign calcifying epithelioma’ .
- Keratin horn formation.
- Malignant change, which is very rare.
The uninfected sebaceous cyst should be removed to prevent possible complications. A small elliptical skin incision is made around the punctum of the cyst under local anaesthetic; the capsule is identified and the cyst removed intact. Failure to remove the cyst in its entirety may lead to recurrence.
If the cyst is acutely inflamed, incision and drainage will be required, followed later by excision of the capsule wall.