32748 A case series of pediatric cellular neurothekeomas and a review of the histologic spectrum

Abstract

Neurothekeomas are rare, benign neoplasms of unknown histogenesis. These neoplasms are a frequent source of diagnostic challenge due to their incompletely defined clinical and morphologic spectrum. Clinically, they may present as a solitary, slow-growing papule or nodule on the head, neck, or extremities of younger individuals, with a slight female predominance. They have traditionally been classified into 3 histologic variants: classical (myxoid), cellular, and mixed, depending on immunohistochemical (IHC) staining and the amount of myxoid matrix. Although the classical variant is believed to be derived from neural sheath cells due to positive S-100 staining, the cellular variant is presumably derived from perineural or dermal lineage. IHC findings for cellular neurothekeomas are typically positive for NKI/C3, smooth muscle actin (SMA) and neuron-specific enolase (NSE), while negative for epithelial membrane antigen (EMA) and S-100. There have been few reports of a rare myxoid cellular neurothekeoma entity that presents with histologic features of the myxoid variant combined with IHC findings of the cellular variant. We herein report a case series of 3 pediatric patients diagnosed with cellular neurothekeoma, particularly highlighting 2 unusual case of a myxoid cellular neurothekeoma with atypical IHC that was negative for NKI/C3, SMA, and NSE as well as negative for S-100. In addition to reporting on our institutional experience with 3 clinical cases of cellular neurothekeomas in a pediatric population, we will explore the histologic spectrum and discuss the current understanding of cellular neurothekeomas.