Granular Cell Tumours (GCTs) are rare subepithelial lesions that are believed to develop from Schwann cells and are characterized by large polygonal cells with abundant lysosomes. Pilot studies from our laboratory showing unexpected HLA-DR immunoreactivity in GCTs lead us to hypothesize that GCTs have an antigen presenting cell (APC) phenotype.
To test our hypothesis, we assessed immunoreactivity of GCT lesions to APC phenotype markers, including CD68, HLA-DR, CD163, CD40 and CD11c. In addition, we assessed markers of neural crest cell (NCC) origin S100, SOX10, NSE and GAP43. Samples subjected to these studies included 23 cases of GCTs and 10 cases of Schwannomas, used as comparators. To confirm the key findings, we detected transcript levels of select genes using quantitative polymerase chain reaction.
We identified a new NCC marker for GCTs, GAP43. We also provide evidence of an APC phenotype of GCTs, as determined from CD68 and HLA-DR immunoreactivity. Due to the limited nucleic acid yield from paraffin-embedded GCT sections, we were unable to draw conclusions from transcript assessment
