AN S100 NEGATIVE GRANULAR-CELL TUMOR WITH MALIGNANT POTENTIAL - REPORT OF A CASE

Malignant granular cell tumors are rare, bur exhibit typical histologi c, immunohistochemical, and electron microscopic features that also ch aracterize their benign counterparts, Although most granular cell tumo rs are S100 protein positive, we report an S100 negative granular cell tumor with histopathologic evidence supporting malignancy. This tumor is best categorized as a malignant granular cell tumor rather than a granular cell variant of a malignant histiocytic, mesenchymal, or epit helial neoplasm. A multidisciplinary approach is essential to diagnosi s.