Intraneural granular cell tumor: Histologic spectrum and histogenetic implication

Abstract

Granular cell tumor (GCT), despite its putative neural origin, commonly occurs in extraneural sites; only six single case reports of intraneural GCT have been described.We report an unique case as the only one with motor dysfunction, the longest duration of symptoms, and largest tumor size with resultant muscle atrophy and fatty infiltration. Upon review of these cases, the striking feature of intraneural GCT lies in its histologic variety, ranging from benign GCT, through plexiform, hybrid GCT and perineurioma to malignant GCT, encompassing the full spectrum of extraneural GCT.As the immunophenotypes of schwannoma and GCT are not exactly identical, together with evidence from ultrastructural studies, the more reasonable and likely possibility is that GCT originates from undifferentiated mesenchymal cells acquiring partial schwannian differentiation. Such postulation by virtue of the widespread occurrence of mesenchymal cells in the soft tissue, better explains the topographic distribution of GCT in extraneural and intraneural location. K E Y W O R D S granular cell tumor, histogenesis, histologic spectrum, intraneural, nerve

Melan-A-Positive Granular Cell Tumor With Extensive Intraneural and Perineural Spread: A Rare Case Report

“…GCTs are an uncommon lesion that can occur in any anatomical location, but they most commonly affect extraneural sites, notably the skin or subcutaneous tissue [3]. While it is widely accepted that GCTs are of Schwann cell origin [3], some researchers have postulated the possibility that GCTs originate from undifferentiated mesenchymal cells that acquire partial Schwannian differentiation [4]. Some benign examples may cause concern for malignancy due to focal nuclear pleomorphism, prominent nucleoli, perineural invasion, and scattered mitoses.…”

Unraveling the Mysteries of Perineural Invasion in Benign and Malignant Conditions

“…Stemm et al conducted a study of 50 GCT, 4 of which demonstrated PNI [113]. Chow et al described seven cases of GCTs forming within a nerve, as opposed to the typical extra-neural presentation [114]. Given their derivation from Schwann cells, it is unclear if PNI by GCTs is due to the inward invasion of the nerve or the tumor's extension out of the nerve from its origin.…”