Abstract: A systematic immunohistochemical investigation of S-100 protein was performed on 168 cases of various neoplastic tissues with anti-S-100 protein polyclonal and monoclonal antibodies.S-100 protein was observed in glioma,Schwannoma,neurofibroma,traumatic neuroma,malignant Schwannoma and“Triton”tumor.S-100 protein was also detected in pigmented nevus,melanoma,liposarcoma,chondrosarcoma and salivary gland tumors.Espe-cially,we have demonstrated S-100 protein in eosinophilic adenoma and medullary carcinoma of thyroid gland,adenocarcinoma of bile duct and bronchiolar adenocarcinoma.The value of S-100 protein on tumor dignosis was discussed.

Key words: S-100 protein, immunohistochemistry, tumor