Sox10 Nuclear Immunostaining Lacks Diagnostic Utility for CNS Granular Cell Tumors

Abstract

Sox10 immunohistochemistry has recently been shown to have diagnostic utility in differentiating typical granular cell tumors (GCTs) in skin and soft tissue from histological mimics (1–3). The overwhelming majority of cases studied have been of cutaneous origin (1–3), although Karamchandani et al included an unspecified number of soft tissue, laryngeal, and esophageal examples (2), and Heerema et al added 2 esophageal GCTs and 2 GCTs of neurohypophysis (3). All tumors from cutaneous and deep sites demonstrated strong diffuse nuclear immunoreactivity for Sox10, while the 2 neurohypophyseal examples were negative (3). To our knowledge, CNS GCTs, which are usually of high-grade astrocytic origin (4), have not yet been explored Given the important role of this transcription factor in neural crest, peripheral nervous system, and CNS development (albeit particularly for oligodendrocyte, not astrocytic, maturation in the CNS) (5), we hypothesized that CNS granular cell tumors might show Sox10 nuclear expression. Therefore, we immunostained CNS GCTs utilizing a polyclonal commercial antibody (Cell Marque Corp., Rocklin, CA). We first paralleled and extended the previous work with a study of 9 cutaneous (Fig. 1A) and 7 deep tissue GCTs from esophageal, colon, breast (n = 2), tongue, lung carina, and tracheal sites. These had been previously characterized at the time of initial diagnosis with hematoxylin and eosin (H&E) stain alone, S100 immunostaining (Fig. 1B), or additional antibodies, but not Sox10. All granular …