Overexpression of p34(cdc2) has been demonstrated in a variety of human cancers and found to be significantly associated with the tumor size, lymph node metastasis, clinical stage, and prognosis of these cancers. In this study, we examined the expression of p34(cdc2) in 81 specimens of oral squamous cell carcinoma (OSCC), 95 specimens of oral epithelial dysplasia (OED; 29 mild, 43 moderate, and 23 severe OED cases), and 14 specimens of normal oral mucosa (NOM) by immunohistochemistry. The cytoplasmic p34(cdc2) labeling indices (LIs) in OSCC, OED, and NOM samples were calculated and compared among the groups. Correlations of the cytoplasmic p34(cdc2) LIs in OSCCs with clinicopathological parameters and survival of OSCC patients were analyzed statistically. We found that the mean cytoplasmic p34(cdc2) LIs significantly increased from NOM (6% +/- 7% ) through mild (18% +/- 10%), moderate (23% + /- 11%), and severe OED (40% +/- 22%) to OSCC samples (73% + /- 20%, p=0.000). A significant correlation was found between the higher mean cytoplasmic p34(cdc2) LIs and positive regional lymph node metastases (p=0.013), more- advanced clinical stages (p=0.022), and higher differentiation of cancer cells (p=0 .027). Our results suggest that the p34(cdc2) expression is an early event in oral carcinogenesis and may play an important role in oral carcinogenesis. Cytoplasmic p34(cdc2) LIs can be used as a biomarker to predict the progression of OSCCs in Taiwan. ; 附設醫院內科部 ; 醫學院附設醫院 ; 期刊論文