Is This An Epidermal Cyst?
A 15-year-old female came to clinic for a round lesion on the anterolateral right neck that was slowly increasing in size over several months. She had noted it being 1/2 a pea-size and now it was almost pea-sized. She had squeezed it and a small amount of whitish, thick material had come out of it. Afterwards the size had decreased for a while but then increased. She also noted that there seemed to be a dark spot over the lesion’s center. It was not painful or erythematous. She denied additional lesions. The family history was positive for other family members with similar lesions.
The pertinent physical exam showed a well-appearing female with normal vital signs and growth parameters. The mass was ~12 mm wide and made the skin slightly elevated but appeared to be part of the skin and not subcutaneous tissue. It was freely mobile, without pain or erythema. There was a punctum noted with brownish coloring of what appeared to be dried material. The rest of her skin examination found freckling of her nose and cheeks and one cafe-au-lait lesion on her left ankle. The rest of her examination was normal. The diagnosis of an epidermal cyst was made. The patient and parents were told about the natural history of the lesion including that they may spontaneously drain, become infected, and rupture causing an inflammatory response. They were also counseled that more lesions can occur. The patient initially decided to monitor, but when the lesion continued to increase in size she decided to have it excised. She had no complications, but did develop another lesion 3 years later on her back that she also had excised.
Epidermal cysts (sometimes called sebaceous, pilar, or epidermoid cysts) are common lesions. They often appear round, firm and are mobile, and a pore may be seen over the mass. They are closed sacs with a definite wall that are intradermal or subcutaneous in location, and occur because of epidermal cell proliferation. Spontaneous drainage of cheesy whitish material (possibly foul-smelling) from the pore may occur. Aspirates may show keratin but usually are highly cellular. They can be singular or multiple and are commonly seen on the head, neck and trunk. Breast and bone sites have also been reported. The lesions are benign and usually cause more cosmetic problems. Potentially however, a lesion’s location or size could make excision necessary for functional reasons.
Rupture of the cyst’s wall may set up an inflammatory reaction where the mass becomes red, swollen and tender and may look like a staphylococcal furuncle. Furuncles usually occur abruptly and drain pus and therefore the difference is usually made based upon the timing of the lesion’s appearance and the drainage material if present. Inflamed cysts have a higher rate of bacteria (aerobic and anaerobic) than uninflamed cysts and therefore may be treated with antibiotics. A tetracycline-type antibiotic may be used for its antibiotic activity and to decrease the inflammatory reaction. Ruptured cysts are also treated with local heat and drainage if necessary. Inflamed cysts often fragment if excision is attempted so usually they are monitored until the inflammation has abated and then excision can be attempted. Surgical excision of the entire cyst wall is necessary so there is no recurrence.
The differential diagnosis of an epidermal cyst includes:
- Brachial cleft cyst (in the neck)
- Ganglion cyst
- Lymph nodes
- Neoplasm of skin
- Neoplasm of adjacent structure
Occasionally history and physical examination may still leave a lesion to be indeterminant. Dermal ultrasound may assist in differentiating between some of the common lesions. A nice image of the ultrasonic appearances of a lipoma, ganglion cyst and epidermal cyst can be seen here. A brief overview of ganglion cysts can be found here. Ganglion cysts are not true cysts because they do not have a true wall. A ganglion cyst is an outpouching of the tendon sheath.
Questions for Further Discussion
1. What are indications for referral to a dermatologist?
2. What other common benign “lumps and bumps” come to a pediatrician’s attention?
- Specialty: Dermatology
- Age: Teenager
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
To view current news articles on this topic check Google News.
To view images related to this topic check Google Images.
Pariser RJ. Benign neoplasms of the skin. Med Clin North Am. 1998 Nov;82(6):1285-307, v-vi.
Handa U, Chhabra S, Mohan H. Epidermal inclusion cyst: cytomorphological features and differential diagnosis. Diagn Cytopathol. 2008 Dec;36(12):861-3.
Kuwano Y, Ishizaki K, Watanabe R, Nanko H. Efficacy of diagnostic ultrasonography of lipomas, epidermal cysts, and ganglions. Arch Dermatol. 2009 Jul;145(7):761-4.
ACGME Competencies Highlighted by Case
1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
2. Essential and accurate information about the patients’ is gathered.
3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
4. Patient management plans are developed and carried out.
5. Patients and their families are counseled and educated.
7. All medical and invasive procedures considered essential for the area of practice are competently performed.
8. Health care services aimed at preventing health problems or maintaining health are provided.
9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.
10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.
17. A therapeutic and ethically sound relationship with patients is created and sustained.
18. Using effective nonverbal, explanatory, questioning, and writing skills, the healthcare professional uses effective listening skills and elicits and provides information.
19. The health professional works effectively with others as a member or leader of a health care team or other professional group.
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital