IMMUNOHISTOCHEMICAL ANALYSIS OF P27 KIP1 EXPRESSION IN THYROID-CARCINOMA/

Cyclin-dependent kinase inhibitors, including the protein product of t he p27/lcip1 gene, play an important role in cell-cycle regulation. Lo ss of p27 expression was reported in a number of neoplasms and shown t o be an independent prognostic factor in colorectal, lung, and breast carcinoma By immunohistochemical analysis, we investigated p27/kip1 ex pression, using a polyclonal antibody, in a series of 87 benign and ma lignant thyroid neoplasms. We correlated its expression with the Ki-67 labeling index and other prognostic factors. All of the thyroid neopl asms examined exhibited significantly lower p27 expression than did no rmal thyroid tissue (P <.001), Poorly differentiated carcinomas had th e lowest p27 staining frequency of all carcinomas examined. p27 staini ng frequency of the papillary carcinomas was significantly lower than that of the follicular carcinomas (P <,001), This difference could not be attributed solely to the inverse correlation between the staining patterns of p27 and Ki-67, which was reported for other neoplasms, bec ause there was no significant difference between the Ki-67 labeling in dices of these two groups. The follicular variant of papillary carcino ma had a significantly higher p27 staining frequency (P =.05) than did classical papillary carcinoma. We saw no significant difference in th e p27 staining frequencies between minimally and widely invasive folli cular carcinomas nor between localized and nonlocalized papillary carc inoma In summary, the p27 immunostaining pattern of thyroid neoplasms is related to neoplastic transformation and varies according to tumor phenotype, It seems, however, to have limited routine diagnostic or pr ognostic significance in thyroid neoplasia.