, Corinna Eleni Psomadakis2 and Bobby Buka3
Department of Family Medicine, Mount Sinai School of Medicine Attending Mount Sinai Doctors/Beth Israel Medical Group-Williamsburg, Brooklyn, NY, USA
School of Medicine Imperial College London, London, UK
Department of Dermatology, Mount Sinai School of Medicine, New York, NY, USA
KeywordsEpidermal inclusion cystEpidermoid cystCystSebaceous cystTumorGrowthNeoplasmInflamedInflammationSubcutaneousExcisionIntralesional steroidCorticosteroidInjectionIncision and drainagePunch excision
These lesions are often misdiagnosed as infectious, but the inflammation seen here is a foreign body reaction to keratin
Primary Care Visit Report
A 36-year-old female with no past medical history presented with a bump on her right shoulder, which had been present and unchanged for years. However, a few days prior to this visit, it became red, tender, and painful . She felt well otherwise.
Vitals were normal. On exam, on her right posterior shoulder, there was a 1 cm × 1 cm erythematous papule that was tender to palpation and indurated.
The diagnosis was uncertain, and the patient was referred to dermatology for further evaluation.
Discussion from Dermatology Clinic
Epidermal inclusion cyst (EIC)
Patient history is suggestive of a ruptured and inflamed EIC .
Epidermal inclusion cysts (EIC), also called epidermoid cysts , are epithelial-lined cysts filled with keratin and lipid-rich debris. The term sebaceous cyst is also commonly used; however, it is inaccurate, as the cysts neither involve sebaceous glands nor contain sebum.
EICs can occur at any age and on any part of the body, although they are more likely to appear in adults . They frequently appear on the chest, back, face, neck, and scalp. The most common cause is occlusion of the pilosebaceous unit. They may also be caused by trauma, when penetration by an object may cause implantation of epidermal cells into deeper tissue of the dermis, or by congenital sequestration of a collection of epidermal cells. Hereditary diseases such as Gardner syndrome, pachyonychia congenita, and Gorlin syndrome all feature multiple EICs.