Soft tissue, granular cell tumour, S100 stain

Granular cell tumours are benign tumours, most likely of nerve sheath cells, that can occur at any body site. This is a case showing a well demarcated neoplasm with irregular borders comprised of nests and sheets of monomorphous round cells. Cytoplasm is abundant, granular and amphiphilic. Nuclei are bland, round hyperchromatic with occasional nucleoli; mitotic figures are not conspicuous (1 per 10 HPFs [FD - 0.55 mm]). Stroma consists of thick collagen bundles and entrapped fat cells. Necrosis is not identified. This slide shows strong diffuse S100 staining.