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Table of Contents
Year : 2022  |  Volume : 19  |  Issue : 1  |  Page : 64-65

Intramuscular epidermoid cyst of flexor carpi ulnaris: A rare occurrence

Department of Radiology, St. John's Hospital, Bengaluru, Karnataka, India

Date of Submission15-Jul-2021
Date of Decision31-Aug-2021
Date of Acceptance12-Oct-2021
Date of Web Publication06-Dec-2021

Correspondence Address:
Ravikanth Reddy
Department of Radiology, St. John's Hospital, Bengaluru - 560 034, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/am.am_75_21

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How to cite this article:
Reddy R. Intramuscular epidermoid cyst of flexor carpi ulnaris: A rare occurrence. Apollo Med 2022;19:64-5

How to cite this URL:
Reddy R. Intramuscular epidermoid cyst of flexor carpi ulnaris: A rare occurrence. Apollo Med [serial online] 2022 [cited 2022 Sep 25];19:64-5. Available from: https://apollomedicine.org/text.asp?2022/19/1/64/331848

  Description Top

A 32-year-old gentleman presented with soft-tissue swelling of the forearm for 4 months. There was a history of trauma to the site of lesion 4–5 years ago. The lesion is nontender, firm and of approximately size 3.5 cm × 4.5 cm located beneath the subcutaneous plane along the flexor aspect of forearm approximately 15 cm from the elbow joint. High-resolution ultrasonography of the lesion demonstrated a well-defined cystic lesion measuring 3.5 cm × 4.5 cm with multiple internal septations and coarse internal echoes and debris [Figure 1]a.The lesion appeared heteroechoic in echotexture due to the presence of fat as intralesional content with superimposed infection. However, the lesion did not demonstrate vascularity on color Doppler [Figure 1]b. The intramuscular lesion was located in the mid third of flexor carpi ulnaris. The patient for referred to the department of general surgery for excision of the lesion. Histopathology revealed a cystic choristoma filled with keratin flakes, cholesterol clefts, degenerated blood components, and lined by stratified squamous epithelium with absent sebaceous glands [Figure 2].Based on imaging and histopathology findings, the patient was diagnosed with intramuscular epidermoid cyst of flexor carpi ulnaris muscle.
Figure 1: (a) High resolution ultrasonography image demonstrating a well-defined cystic lesion in the intramuscular location with multiple internal septations and coarse internal echoes. (b) Color Doppler ultrasonography image demonstrating absent vascularity within the lesion consistent with features of epidermoid cyst

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Figure 2: Histopathology image demonstrating the lining of the epidermal cyst comprising stratified squamous epithelium with granular cell layer. Note the lack of eccrine glands or sebaceous glands within the wall (H and E, ×200)

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  Discussion Top

Epidermoid cyst, also known as epidermal inclusion cyst, is commonly located deep to the subcutaneous plane. Intramuscular epidermal cyst is an atypical presentation of a relatively common entity and has been very sparsely reported in the literature.[1] Etiopathogenesis is related to trauma and surgical procedures with accidental implantation of lining epithelium and its derivatives within the dermis or intramuscular location. However, there is no evidence to suggest invasion of adjacent structures by the epidermal cyst.[2] High-resolution ultrasonography imaging features of epidermoid cysts include a well-circumscribed, heteroechoic, and predominantly hyperechoic cystic lesion demonstrating coarse internal echoes and septations with echogenic debris. Superadded infection may cause thickening of the wall of the epidermal cyst. Nevertheless, the lesion demonstrates no internal vascularity on color Doppler.[3] Preoperative assessment on high-resolution ultrasonography or magnetic resonance imaging is required for making an accurate diagnosis. In conclusion, intramuscular location of epidermoid is an atypical and rare presentation of the relatively common epidermal inclusion cyst. Nevertheless, the entity needs to be included in the differential diagnosis of soft-tissue mass lesions <5 cm in size, even when found at unusual sites, especially when associated with a history of trauma.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Low SF, Sridharan R, Ngiu CS. Giant epidermal cyst with intramuscular extension: A rare occurrence. BMJ Case Rep 2015;2015:bcr2013202534.  Back to cited text no. 1
Hoang VT, Trinh CT, Nguyen CH, Chansomphou V, Chansomphou V, Tran TT. Overview of epidermoid cyst. Eur J Radiol Open 2019;6:291-301.  Back to cited text no. 2
Yim Y, Kim NR, Moon SG. Intramuscular epidermal cyst of the buttock: A case report. J Korean Soc Radiol 2018;79:354-8.  Back to cited text no. 3


  [Figure 1], [Figure 2]


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