The Open Orthopaedics Journal

ISSN: 1874-3250 ― Volume 13, 2019

Characteristic MRI Findings of Epidermal Cysts Categorized by Size

Akio Sakamoto*, Takeshi Okamoto, Shuichi Matsuda
Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Shogoin, Kawahara-cho 54, Sakyo-ku, Kyoto, 606-8507, Japan



Epidermal cysts are lined with stratified squamous epithelium and filled with keratinous material.Magnetic resonance imaging (MRI) findings can be used for the diagnosis of epidermal cysts, but characteristic MRI findings related to cyst size in particular go unreported.


To analyse characteristic MRI findings of epidermal cysts categorized by size.

Materials and Methods:

Unruptured epidermal cyst cases were analyzed according to 3 cyst size categories: large (≥4 cm), medium (≥2 to <4 cm), and small (<2 cm). MRI assessments focused on the keratinized material using low signal intensity on T2-weighted images because of intracystic diffuse foci (a sign of intracyst debris) and serpentine structures at the periphery (a sign of a peripheral lining) of cysts.


Thirty-three patients (26 males and 7 females; average age, 52.2 years; 33 cases) were grouped by cyst size: large (13 cases), medium (12 cases), and small (8 cases). MRIs revealed cyst walls via low signal intensity on T1- and T2-weighted images. On T1-weighted images, the signal intensity of cysts relative to that of muscle was hypointense (1 case, 3%), isointense (4 cases,12%), and slightly hyperintense (28 cases, 85%). On T2-weighted images, cysts were hyperintense in muscle relative to adipose tissue (20/33 cases, 61%) and isointense relative to adipose tissue (7/33, 21%) or hyperintense relative to adipose tissue (6/33, 18%). Overall, signal patterns were similar among groups. Signs of inner debris were observed in all large (13, 100%) and medium (2/12, 17%) cysts, but not in small cysts (0/8). Large, medium, and small cysts had signs of peripheral linings (12/13, 92%; 9/12, 75%; and 4/8, 50%, respectively).


Slightly hyperintense signals on T1-weighted images were characteristic, even in small epidermal cysts. Signs of intracyst debris and a peripheral lining reflect the pathology and were considered useful for diagnosis. Larger cysts were more frequently positive for keratinous debris.

Keywords: Epidermal cyst, Subcutis, Magnetic Resonance Imaging, Size, Debris, Keratinized material.

Article Information

Identifiers and Pagination:

Year: 2018
Volume: 12
First Page: 462
Last Page: 468
Publisher Id: TOORTHJ-12-462
DOI: 10.2174/1874325001812010462

Article History:

Received Date: 27/05/2018
Revision Received Date: 26/10/2018
Acceptance Date: 29/10/2018
Electronic publication date: 27/11/2018
Collection year: 2018

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© 2018 Sakamoto et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Shogoin, Kawahara-cho 54, Sakyo-ku, Kyoto 606-8507, Japan, Tel: +81-75-751-3366, Fax: +81-75-751-8409, E-mail:


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