[Immunohistology and prognosis in thyroid cancer. Determination of the malignancy potential of papillary and medullary neoplasms by the detection of S-100 protein and Leu-M1 antigen].

170 thyroid carcinomas were investigated for the presence of S-100-protein-positive Langerhans cells (LC) and the expression of Leu-M1-antigen. Dense LC infiltrates were found only in papillary tumours and were shown to be significantly related to prognosis. Irrespective of any other feature, no single instance of death resulting from cancer occurred among 23 tumours (including 6 cases of stage pT4) with dense infiltrates (greater than 20 LC/unit field) while 9/53 (17%) of the remaining patients died from carcinoma (p less than 0.01). The degree of epithelial Leu-M1 expression was significantly related to the biological behaviour of papillary and medullary neoplasms. Death resulting from cancer occurred 17 times more frequently among papillary tumours with marked positivity (greater than 15%) as compared to cases with slight or absent immunoreactivity (8/24 vs. 1/52; p less than 0.00005). Among medullary carcinomas, local recurrences occurred 2.9 times (14/16 vs. 7/23; p less than 0.005) and death resulting from tumour occurred 4.3 times (9/16 vs. 3/23; p less than 0.03) more frequently for intensely stained as compared to slightly immunoreactive and unstained neoplasms.