Immunohistochemical detection of neuroblastomatous foci in composite adrenal pheochromocytoma-neuroblastoma.

To determine if immunohistochemistry might aid in the identification of neuroblastomatous foci in composite adrenal tumors, the authors analyzed two examples of composite adrenal pheochromocytoma-neuroblastoma, 18 pure pheochromocytomas, and six pure neuroblastomas using peanut agglutinin and a panel of antibodies directed against neuroendocrine and neural-associated antigens. Pure pheochromocytoma had the following immunopositivity: vimentin 14/18, chromogranin 18/18, synaptophysin 18/18, S100 protein 0/18 (tumor cells), neurofilament 14/18, J1 beta-tubulin (J1) 18/18, microtubule-associated protein-2 13/18, glial fibrillary acidic protein 13/18, and peanut agglutinin 17/18. Pure neuroblastoma reacted positively as follows: vimentin 0/6, chromogranin 5/6, synaptophysin 4/6, S100 protein 0/6 (tumor cells), neurofilament 5/6, J1 6/6, microtubule-associated protein-2 6/6, glial fibrillary acidic protein 1/6, and peanut agglutinin 6/6. Each component of both composite tumors reacted similarly to the pure neoplasms. Although the frequency of positive staining was similar for pheochromocytoma and neuroblastoma, the intensity and pattern differed for several antigens. Pheochromocytoma was diffusely positive for synaptophysin and chromogranin, whereas staining was focal and punctate in neuroblastoma. Microtubule-associated protein-2, J1, and neurofilament antibodies highlighted the fibrillar background of neuroblastoma, which pheochromocytoma lacked. Pheochromocytoma contained focal, ball-like immunoreactivity for glial fibrillary acidic protein and vimentin, which was absent in neuroblastoma. These immunohistochemical distinctions can assist the clinically important recognition of neuroblastomatous foci in composite adrenal pheochromocytoma-neuroblastoma.