Microreticular perineurioma: a new morphological subtype of a rare entity.

Perineurioma is a benign peripheral nerve sheath tumor. Several subtypes have been described, including plexiform, reticular, and sclerosing. The reticular variant has been previously described as having a net or lace-like growth pattern consisting of large anastomosing cords of spindle-shaped cells. We report a case of an 11-year-old male who presented with a two-year history of a slowly enlarging, tan-white lesion on the finger. Microscopically, the lesion consisted of cells with ovoid nuclei and delicate, elongate cytoplasmic processes, arranged in a microreticular pattern. The lesional cells were markedly positive for epithelial membrane antigen (EMA) and claudin-1. Based on these features and the unusual morphology, the case was called a microreticular perineuroma. The patient underwent complete excision of the lesion with no recurrence nine months after follow-up. To our knowledge, this is the first reported case of this morphologic variant. Awareness of this entity is important to avoid inappropriate management. This article is protected by copyright. All rights reserved.