Immunocytochemistry of paragangliomas--value of staining for S-100 protein and glial fibrillary acid protein in diagnosis and prognosis.

Surgical specimens of 65 adrenal and 27 extra-adrenal paragangliomas, the latter comprising 11 carotid body, five jugulotympanic, one aorticopulmonary, eight aorticosympathetic and two visceral autonomic tumours, were examined immunocytochemically for the presence of glial fibrillary acid protein (GFAP) and S-100 protein. Six adrenal and four extra-adrenal (one parasympathetic and three sympathetic) neoplasms pursued a malignant clinical course. S-100 staining of sustentacular (type 2) cells was seen in both adrenal (48/65) and extra-adrenal (23/27) lesions, the 10 malignant tumours being entirely devoid of S-100 protein positive cells. GFAP positivity of type 2 cells was seen in only 16 of the extra-adrenal tumours, all of these lesions belonging to the group of benign parasympathetic paragangliomas. The presence of S-100 positive type 2 cells may thus help to exclude malignancy in individual paraganglioma cases, while GFAP positivity of such cells renders possible the correct typing of benign parasympathetic paragangliomas.