Granular Cell Tumor
Granular cell tumors are composed of round, polygonal, or spindle-shaped cells with nuclei ranging from small, hyperchromatic, pyknotic (as seen in this image) to large vesicular nuclei with punctate nucleoli. Occasional nuclei may show intranuclear pseudoinclusions or degenerative-type atypia. The cytoplasm is eosinophilic with fine to coarse granules as well as large round droplets that are PAS-positive, diastase-resistant. These granules represent phagolysosomes accumulated in the cytoplasm. Ultrastructurally, they appear as membrane-bound vacuoles containing myelin figures, fragmented rough endoplasmic reticulum, and mitochondria. In addition, there is a second population of cells with angulated bodies. There is replicated basal lamina material around the granular cells.