Granular Cell Tumor : S-100

Granular cell tumor (GCT) is a benign neural tumor containing polygonal cells with abundant granular eosinophilic cytoplasm. They present as small painless nodules in the dermis, subcutis, or mucosal surfaces. Intraoral sites (tongue, oral mucosa, hard palate) are frequently involved. Less common sites include deep soft tissues and visceral organs. Patients are usually adults; F:M=2:1. GCTs have ill-defined margins and an infiltrative growth pattern. The tumor cells are arranged in nests, ribbons, or sheets and have abundant eosinophilic granular cytoplasm. The overlying surface frequently shows pseudoepitheliomatous hyperplasia mimicking squamous cell carcinoma. The cytoplasmic granules are PAS+ve, diastase-resistant and represent phagolysosomes. The nuclei may be small and pyknotic or vesicular with punctate nucleoli. GCTs are positive for S-100 protein, NSE, laminin, calretinin, myelin proteins (P0, P2), and CD68. They are negative for neurofilament protein and GFAP. GCT should be distinguished from rhabdomyoma, hibernoma, fibroxanthoma, as well as reactive histiocytic proliferations in sites of trauma/surgery. Most granular cell tumors are benign and cured by simple resection. Reference: Enzinger & Weiss's Soft Tissue Tumors, Sixth Edition, 2014; p. 838-843. Updated: May 2nd, 2017.