These 2 swellings on the scalp of a 13-year-old boy had appeared about 8 months earlier and had slowly enlarged. The mother had massaged the lesions when they were small in an attempt to heal them. There was no history of local trauma (eg, from hair-cutting tools) and no pain or discharge from the lesions.
A clinical diagnosis of epidermal inclusion cysts (EICs) was made. EICs occur predominantly in teens and middle-aged adults, without any racial or sexual predilection. They rarely appear before puberty. An earlier onset should suggest an alternative diagnosis.1,2
Injury, sun damage, androgen secretion at puberty, or infection with human papilloma virus may cause occlusion of the pilosebaceous unit, which leads to cyst formation. Gardner syndrome, an autosomal-dominant variant of familial adenomatous polyposis, is associated with intestinal polyps, multiple osteomas, and skin and soft tissue tumors (including EICs).
An EIC--also known as a wen or epidermoid, infundibular, or sebaceous cyst--is surrounded by stratified squamous epithelium and a well-formed granular layer wall that communicates with the surface through a narrow keratin-filled channel.3 This usually solitary, subcutaneous, round, smooth swelling ranges in size from a few millimeters to several centimeters. The overlying skin may be shiny, and a small opening (a blackhead) may be present.4 The lesion is commonly found on the face, trunk, neck, extremities, and scalp. In other areas, it may cause symptoms. For instance, oral cysts may make it difficult for the patient to breathe, swallow, or speak. Dyspareunia or dysuria can occur with genital lesions. Subungual and plantar lesions may interfere with walking.2
EICs are painless and mobile on palpation. They may become painful and inflamed if they rupture or become infected (which is rare).3 Cultures are usually negative or grow Staphylococcus epidermidis and Propionibacterium, which may be skin contaminants.2 The sterile purulent material either drains out or is slowly reabsorbed. Antibiotic treatment is not required on a routine basis.1
Malignancies, such as basal cell carcinoma, Bowen disease, squamous cell carcinoma, and mycosis fungoides, have rarely developed in epidermoid cysts.4 Risk factors for malignant transformation include neonatal onset, history of rapid and progressive growth, skin ulcerations, fixation to or location deep into the fascia, and size greater than 3 cm in diameter.5
The differential diagnosis of EIC includes superficial lymph nodes, lipomas, bronchogenic duct cysts, pilar cysts (or trichilemmal cysts), pilomatrixomas, dermoid cysts, and steatocystoma multiplex.6 Pilar cysts comprise the majority of scalp lesions. Histopathological examination may be necessary to confirm the diagnosis.
Asymptomatic EICs can be removed for cosmetic reasons or if they affect function. A fluctuant or inflamed cyst must be evacuated.2
This patient was referred to a pediatric surgeon who excised the cysts. Biopsy results confirmed the diagnosis. *
REFERENCES:1. James WD, Berger TG, Elston DM, eds. Andrew's Diseases of the Skin: Clinical Dermatology. 10th ed. Philadelphia: Saunders; 2006:676-679.2. Kenneth AB. Epidermal inclusion cyst. EMedicine Web site. Available at: http://www.emedicine.com/derm/topic860.htm. Accessed June 5, 2007.3. Habif TP, ed. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. Philadelphia: Mosby; 2004:717-719.4. Julie SP. Diseases of the dermis and subcutaneous tissues: nodular diseases. In: Schachner LA, Hansen RC, eds. Pediatric Dermatology. 2nd ed. New York: Churchill Livingstone; 1996:811-818.5. Knight PJ, Reiner CB. Superficial lumps in children: what, when, and why? Pediatrics. 1983;72:147-153.6.Golden BA, Zide MF. Cutaneous cysts of the head and neck. J Oral Maxillofac Surg. 2005;63:1613-1619.