Methods. Immunoreactivity for epithelial membrane antigen (EMA), cytokeratin, and vimentin was investigated in 15 papillary thyroid carcinomas (PTC) with distant metastases, 25 PTC without distant metastases, and 34 occult PTC without distant metastases that were found incidentally at autopsy.
Results. More than 50% of the tumor cells were positive for EMA in 7 (47%) of 15 PTC with distant metastases, 0 (0%) of 25 PTC without distant metastases, and 1 (3%) of 34 occult PTC. The incidence of EMA positivity in PTC with distant metastases was significantly different from that of both PTC without distant metastases and occult PTC (P < 0.001). Cytokeratin reactivity was similar in the three groups, and almost all PTC stained strongly for cytokeratin. Concerning vimentin positivity, there were no significant differences in the three groups; however, PTC with distant metastases tended to stain more weakly or focally than PTC without distant metastases or occult PTC.
Conclusions. These results suggest that EMA reactivity may be a useful factor for anticipating the individual risk of distant metastasis or death from PTC at the time of initial surgical treatment. Cancer 1992; 70: 2326-2333.