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Case Reports

Abstract

Epithelial sheath neuroma (ESN) is a rare cutaneous neoplasm comprised of neural and epithelial elements, with very few cases reported. Debate surrounds its classification as a benign tumor, hamartoma, or unusual reactive hyperplasia. Here we present four cases.

Case 1: A 46-year-old woman with history of renal transplant and multiple skin cancers presented with a tender, erythematous forearm lesion, initially diagnosed as squamous cell carcinoma (SCC) with perineural involvement. Excision revealed a proliferation of nerve bundles surrounded by benign squamous epithelium with a reactive fibromyxoid stroma and no connection to the epidermis. There were no signs of regression, cytologic atypia or mitoses in the squamous epithelial aggregates, consistent with a diagnosis of ESN rather than SCC.

Case 2: A 59-year-old male had a crusted erosion on the left clavicle suspected to be basal cell carcinoma (BCC). Microscopic examination showed an ESN and scar tissue.

Case 3: A 67-year-old female underwent excision for an upper chest lesion. Histologic sections revealed BCC and ESN. Ber-EP4 staining was positive in the basaloid proliferation, but negative in squamoid islands with associated nerve bundles.

Case 4: A 64-year-old male had an upper back nodule. The clinical impression was BCC. Histologic findings demonstrated an ESN. The squamoid areas were positive for CK AE1/AE3, CK5/6, and p63.

While neuroepithelial structures with surrounding fibromyxoid stroma in skin biopsies can be worrisome for SCC with perineural invasion, the absence of epidermal attachment, cytologic atypia, and prior history of SCC aid in recognition of ESN and prevent overdiagnosis and treatment.