A Retrospective Chart Review of Inflamed Epidermal Inclusion Cysts

February 2021 | Volume 20 | Issue 2 | Editorials | 199 | Copyright © February 2021

Published online December 18, 2020

Harry Meister , Marc Taliercio , Nahla Shihab MD

Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, NY

Background: Epidermal inclusion cysts (EIC) are one of the most common forms of cysts found on and/or underneath the skin. Inflamed EICs typically show signs and symptoms such as pain and erythema, mimicking cutaneous abscess. However, prior studies have demonstrated at least 20% of lesions are culture negative.
Objective: To determine the rate of culture positivity in mild inflamed epidermal inclusion cysts, in particular to identify whether empiric antibiotics are warranted.
Methods: In a retrospective chart review 76 cases of inflamed EIC that were mild (lacking systemic symptoms) were analyzed who presented to the department of dermatology at Mount Sinai between 2016–2019.
Results: Of cultures taken from inflamed cysts, 47% resulted in no bacterial growth or growth of normal flora, 38.4% resulted in growth of aerobic bacteria with methicillin-resistant Staphylococcus aureus (8%), Staphylococcus lugdunensis (5%), and methicillin-sensitive Staphylococcus aureus (13%) predominating, and 9.3% resulting in growth of anaerobic bacteria with Finegoldia magna, Peptostreptococcus, and Cutibacterium acnes presenting. Review of prescribed treatment regimens often involved antibiotic medication, despite a high prevalence of negative culture.
Conclusions: Almost half of cases of mild inflamed EIC (lacking systemic symptoms) cultured will not grow pathogenic bacteria, therefore incision and drainage with culture and appropriate therapy is a viable therapeutic option in uncomplicated inflamed EIC lesions. In this way, over prescription of antibiotics can be minimized.

J Drugs Dermatol. 20(2):199-202. doi:10.36849/JDD.2021.5014


Epidermal inclusion cyst (EIC) is one of the most common acquired skin cysts. It originates from the proliferation of epidermal cells that lost connection to the surface, forming a closed sac with a definite wall. EIC can be found in any area of the body, typically presenting as nodules under the skin, along with a visible central punctum. EIC may become enlarged, inflamed, infected, or remain stable; however, there are no factors that reliably predict whether the cyst will become inflamed or not. If inflammation does occur, the cyst becomes symptomatic, typically red and painful, mimicking active abscess infection. It may rupture spontaneously or may require surgical drainage followed by a course of systemic antibiotics. The source of infection usually comes from normal skin flora organisms, colonized bacteria or other potential pathogens.1

Overprescribing of antibiotics in dermatology is a timely topic. A recent article has highlighted 35.4% rise in the usage of short-term antibiotics for cysts between 2008 and 2016, despite an overall reduction in antibiotic usage, supporting the need for improved antibiotic prescribing in the setting of cysts.2 The aim of this study was to determine whether bacterial infection plays a significant role in inflamed EIC, and evaluate treatment regimens utilized.


After institutional review board exception, researchers compiled and recorded data on patients who presented with inflamed EIC (s) to the Department of Dermatology at Mount Sinai. Inflamed EIC was defined as a mobile cyst that was surrounded by erythema and contained a localized collection of purulent material. Patients with systemic symptoms such as fever or malaise were excluded from review. The inclusion criteria for chart review were dermatologic evaluation, presence of a clinically diagnosed EIC and performance of bacterial culture on the contents of the diagnosed EIC. One hundred-six patients with EIC were identified but only 76 patients met study criteria. The researcher(s) recorded patient age, sex or gender, location of the cultured EIC including laterality, comorbidities, culture results and type (aerobic, anaerobic, or both), and the courses of treatment (including incision and drainage, intralesional