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At least four benign mimics of microscopic PNI exist, important in the differential diagnosis of microscopic PNI. Knowledge of these entities should help dermatopathologists to correctly distinguish them from PNI and avoid unnecessary additional treatment.

Here, a case of a rare epithelial sheath neuroma (ESN) is reported. A 49-year-old white female presented with a 5 mm solitary, slightly raised, erythematous, itchy papule on her right upper back. The clinical impression was consistent with an inflamed nevus. The patient had no past medical history of malignancy or a family history of neurofibromatosis. There was no prior trauma, surgical procedures, or skin disease at the site. After excision, the patient has had no recurrence at the surgery site during a 4-months follow-up period. ESN is characterized by enlarged nerve fibers ensheathed by a sometimes keratinized squamous epithelium located in the superficial dermis where large nerves are not normally found. It is believed to be a benign neoplasm and simple excision is curative. The histologic differential diagnosis of ESN is presented, and possible mechanisms of its pathogenesis are discussed. It is important for the pathologist and dermatologist to be cognizant of this lesion to prevent misdiagnosis of perineural invasion.

Background: MART-1, Melan-A, and Tyrosinase have shown encouraging results for evaluation of melanoma micrometastases in sentinel lymph nodes, as compared to conventionally used S-100 protein and HMB-45. To achieve higher sensitivity, some studies recommend evaluation of three sections, each at intervals of 200 µ. This would mean, routine staining of three adjacent sections in each of the three clusters at intervals of 200 µ, requiring nine slides resulting in added expense. If a cocktail of these antibodies could be used, only one section would be required instead of three generating significant cost savings.

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