Immunohistochemical demonstration of the lysosome-associated glycoprotein CD68 (KP-1) in granular cell tumors and schwannomas.

The monoclonal antibody KP-1 that recognizes the lysosome-associated glycoprotein CD68 was used together with antibodies to other antigens (actin, glial fibrillary acidic protein, keratin, neurofilaments, chromogranin, synaptophysin, S-100 protein, HMB-45, lysozyme, and HLA-DR) in a labeled streptavidin biotin immunoperoxidase method to phenotypically characterize 27 granular cell tumors, five schwannomas, five neurofibromas, two ganglioneuromas, three ganglioneuroblastomas, five carcinoid tumors, five malignant melanomas, and five examples of histiocytosis X. The neoplastic cells in all 27 of the granular cell tumors and four of the five schwannomas strongly stained for CD68, whereas none of the neurofibromas, ganglioneuromas, ganglioneuroblastomas, or carcinoid tumors contained CD68-positive tumor cells. These findings further strengthen previous observations, suggesting a histogenetic relationship between granular cell tumors and Schwann cells. KP-1 reactivity also was demonstrated in cells of histiocytosis X and malignant melanoma, complementing other studies that extend the tumor types positive in immunoperoxidase stains using this antibody.