Arch Hand Microsurg.  2021 Dec;26(4):315-318. 10.12790/ahm.21.0108.

An Epidermoid Cyst along the Sensory Branch of Digital Nerve with Focal Neuropathy: A Case Report

• Oh SH
• Choi SH
• Kim YW

• KMID: 2522632
• DOI: http://doi.org/10.12790/ahm.21.0108

Abstract

An epidermoid cyst is a slow-growing benign neoplasm that commonly occurs in the hand. Herein, we report a rare case of an epidermoid cyst with focal neuropathy in the left ring finger of a 38-year-old woman. Preoperatively, the patient complained of erythema, swelling, and paresthesia on her fingertips. On ultrasonography and magnetic resonance imaging, ulnar digital nerve thickening and inflammation around the nerve were observed, and a neurogenic tumor-like schwannoma was expected. An excisional biopsy with neurectomy of the involved sensory branch of the ulnar digital nerve was performed under brachial plexus block. During the operation, there is such an uncommon morphology, yellowish debris under the epineurium of the ulnar digital nerve sensory branch was involved with the epidermoid cyst and seemed to be propagating along the sensory branch from the skin surface. After the operation, the paresthesia and swelling resolved. Over the 6-month follow-up in the outpatient clinic, no complications and recurrences occurred. Thus, we reported a rare intraneural epidermoid cyst (occurred along the digital nerve) in the finger, and we believe that considering the anatomical characteristics and the surrounding structures is important during mass excision.

Keyword

Epidermoid cyst; Paresthesia; Erythema; Ulnar digital nerve; Excisional biopsy

Figure

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  Fig. 1. The mass with fusiform swelling, pain, and paresthesia on the volar side of the left ring finger 1 month before treatment.

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  Fig. 2. Ultrasonography image showing the swelling and thickening of the ulnar digital nerve (UDN; yellow circle and arrow). A neurogenic tumor was expected. LRF, left ring finger.

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  Fig. 3. Magnetic resonance image showing unencapsulated and segmental thickening (yellow dotted circle, left) with surrounding edema (red dotted circle, right) along the ulnar digital nerve. A neurogenic tumor was expected.

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  Fig. 4. (A) The epidermal cyst containing yellowish debris encircled and involved the sensory branch of the ulnar digital nerve. (B) The epidermal cyst with yellowish debris propagating toward the outer skin. (C) The preserved main branch of the ulnar digital nerve after neurectomy.

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  Fig. 5. Histological examination showing many acute inflammatory cells lined by true epidermis around the digital nerve (H&E stain, ×100).

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  Fig. 6. Six months postoperative appearance showing a full range of motion without any complications and symptoms.

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  Fig. 7. A schematic photograph of the epidermal cyst propagating to the main digital nerve along the sensory branch.

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