An immunohistochemical study of leu 7 and PCNA expression in thyroid neoplasms

Monoclonal Antibody (MoAb) HNK, or anti-leu-7, is reactive with several neuroendocrine and nonneuroendocrine tumors. The aim of this study is to examine anti-leu-7 reactivity in thyroid neoplasms and its relationship to cellular proliferation as determined by anti-PCNA reactivity. The expression of anti-leu-7 in 56 thyroid neoplasms (24 papillary carcinomas, 14 follicular carcinomas, two medullary carcinomas and 16 follicular adenomas) was examined immunohistochemically. Papillary and follicular thyroid carcinomas reacted with anti-leu-7 in a membranous and cytoplasmic pattern in 88% and 93% of cases, respectively. The adjacent benign tissues were nonreactive. Only eight cases diagnosed as follicular adenomas were reactive with anti-leu-7. Furthermore, the mean proliferative index (PI), as measured by the percentage of nuclei immunoreactive with anti-PCNA, was greater than 30% in all thyroid neoplasms reactive with anti-leu-7. The PI was 58% for papillary carcinomas and 68% and 48% for follicular carcinomas, and follicular adenomas, respectively. Lesions originally classified as follicular adenomas that were nonreactive with anti-leu-7 had a PI of 24% and were reclassified as hyperplastic nodules. These data suggest that anti-leu-7 may be useful for characterizing thyroid neoplasia.