Granular Cell Tumor: A Review of the Pathology and Histogenesis

Abstract

As the name suggests, the histogenesis of the granular cell tumor is uncertain, but this intriguing neoplasm has occasioned much speculation and controversy since its description in 1926 as a myoblastoma. Though ubiquitous in its anatomic location, it is usually small, solitary, benign, and readily recognized by routine light microscopy, and questions concerning it are principally academic. However, a small number of cases are malignant and they can be difficult to identify in paraffin sections. The combined input from immunohistochemistry and electron microscopy has greatly clarified understanding of the morphology of this lesion and both methods are helpful when the differential diagnosis is a problem. The cell of origin is still undecided, and although distinct neural features argue for Schwannian origin, the noncommittal term granular cell tumor continues to be appropriate.

Granular Cell Tumor Located in the Bulbar Subconjunctival Space

“…The diagnosis of GCT is usually made on the basis of its typical features on light microscopy hematoxylin and eosin-stained and PAS sections (small round nuclei and granular cytoplasm that are PAS positive) [4,8]. Due to its neural origin, the tumor frequently stains positive for S-100 protein and neuron-specific enolase [2,3,4,8].…”

“…Due to its neural origin, the tumor frequently stains positive for S-100 protein and neuron-specific enolase [2,3,4,8]. Another marker that frequently stains positive in GCT is CD-68.…”

“…Another marker that frequently stains positive in GCT is CD-68. This was once interpreted as a possible histiocytic origin for GCT, but lately, CD-68 positivity was proved to be a common finding in a variety of lesions rich in lysosomes, thus making this immunomarker not a specific one to GCT [2,3,4,8]. …”

“…Immunohistochemistry and ultrastructural studies have identified GCT to originate from Schwann cells [2,3]. A review by Ordóñez and Mackay [4] concluded that GCT is most frequently located in the head and neck area. About one-fourth of the lesions occurred in the tongue.…”

“…About one-fourth of the lesions occurred in the tongue. Other reported sites are the orbit, larynx, parotids, breast, esophagus, respiratory, gastrointestinal, and genitourinary tracts [4]. …”