Assessment of the proliferative ability of cancer cells is necessary not only for the biologic characterization of tumors, but also for the selection of treatment and evaluation of prognosis. Recently, there have been several studies examining the proliferative activity of various malignant tumors using immunohistochemical methods. PCNA is a nuclear protein related to the cell cycle and found with high expression in proliferative tissues, including cancers.

In our study, to evaluate whether PCNA expression was useful as a prognostic factor in patients with papillary thyroid carcinoma, we quantitated the immunohistochemical expression of PCNA in the formalin-fixed paraffin embedded tissue from 55 patients with papillary thyroid carcinoma and correlated the results with established clinicopathologic parameters.

The results were as follows. 1) PCNA expression in papillary thyroid carcinoma did not correlate with the age, sex or metastatic L/N activity of the patient, nor with the size, invasion, or recurrence of the tumor. 2) There was a close relationship between the expression rate of PCNA in thyroid tumor cells and that in metastatic L/N cells (p=0.056, in p<0.1). 3) The expression of PCNA in the metastatic L/N (+) group was higher than in the metastatic L/N (+) group (p=0.045).

It is suggested that PCNA expression is not an appropriate prognostic factor in papillary thyroid carcinoma.