Epithelial sheath neuroma: evidence supporting a hyperplastic etiology and epidermal origin

Abstract

An epithelial sheath neuroma (ESN) is a rare benign process of unknown pathogenesis, which is characterized histologically by multiple enlarged peripheral nerve fibers ensheathed by mature squamous epithelium. The histologic features can elicit concern for carcinomatous perineural invasion. The process is limited to the superficial dermis and is surrounded by a loose myxoid stroma, lymphocytic infiltrate and sometimes prominent infundibular cysts. The etiology of this peculiar entity has been debated and theories include a benign neoplasm, a hamartoma or an unusual reactive hyperplasia. There are only seven prior cases reported of ESN in the literature. Our case presented here is the first report to show connection of the ESN to the overlying epidermis and reactive epidermal hyperplasia. This suggests that ESN is indeed an unusual form of benign reactive hyperplasia. In addition, the clinical setting in this case was of pruritus and scratching in a background of papular urticaria, supporting the previous notion that ESN is probably a response to an external stimulus such as rubbing.

Epithelial sheath neuroma with extension to the subcutis

“…Each case of ESN reported has been described to be cured with shave biopsy or simple excision . We report the first case of ESN to extend down to the subcutis, demonstrating that not all cases of ESN are confined simply to the superficial dermis.…”

“…Hirano‐Ali et al described a case in a patient with papular urticaria showing a connection to the epidermis and pointed out that there have been several cases of ESN showing overlying epidermal change consistent with lichen simplex chronicus. Moreover, Vandergriff et al reported a case of multifocal ESN with two papules clinically 1 cm apart with an associated acanthotic epidermis on pathology.…”

“…Hirano-Ali et al 5 a case of multifocal ESN with two papules clinically 1 cm apart with an associated acanthotic epidermis on pathology. It is possible that these were two separate lesions, but also reasonable to think they could be one in the same arising as part of a reactive process secondary to the irregularity in distribution of the nerve fibers and stroma characteristic of ESN.…”

“…Histologically, ESN is described to occur in the superficial dermis and is categorized by squamous epithelium surrounding enlarged peripheral nerve fiber proliferations . Zelger and Zelger theorized that ESN may be a reactive process, and Hirano‐Ali et al were the first to report a case of ESN with a direct connection to the epidermis. All reported cases have been noted to be cured by shave biopsy and/or simple excision …”

“…All reported cases have been noted to be cured by shave biopsy and/or simple excision. [1][2][3][4][5][6] 2 | CASE REPORT After the excision, the patient became pain-free over the course of days. The patient has followed up multiple times over 12 months and continued to be pain-free with no recurrence of the lesion to date.…”