Normal thyroid epithelial cells lack major histocompatibility complex (MHC) Class II antigen. Oncogenic kinases involved in papillary thyroid carcinoma (PTC) trigger the expression of Class II transactivator and MHC Class II complex. However, the relationship between MHC Class II antigen expression and clinical outcome in PTC is unknown. To investigate the frequency of MHC Class II antigen expression in PTC and to identify the effects of MHC Class II antigen expression on clinical outcomes in PTC patients, the expression of HLA-DR/-DQ antigen was analyzed in surgical specimens from 77 PTCs and 44 benign nodules (23 nodular hyperplasias, 21 follicular adenomas). Of the 77 PTC cases, 36 (46.8%) cases expressed HLA-DR and 41 (53.2%) cases expressed HLA-DQ. Next, we investigated clinicopathological characteristics and found that HLA-DR(+) and/or HLA-DQ(+) PTC tended to present without nodal metastasis. Multivariate analyses clearly showed that HLA-DR(+) or HLA-DQ(+) PTC has a low risk of recurrence (HLA-DR OR = 0.22, CI, 0.06-0.9; p = 0.03, HLA-DQ OR = 0.25, CI, 0.07-0.9, p = 0.03). The Kaplan-Meier estimate revealed a significantly lower recurrence-free probability in patients with HLA-DR(-) PTC and HLA-DQ(-) PTC (Log-rank test; chi(2) = 4.59 and 6.07, p = 0.03 and 0.01, respectively). In conclusion, PTC frequently expresses MHC Class II antigen, and the expression of MHC Class II antigen correlated inversely with the risk of recurrence of PTC.
(c) 2007 Wiley-Liss, Inc.