The present study sought to explore the occurrence of signal transducer and activator of transcription 3 (Stat3) in patients with oral squamous cell carcinoma (n=135) and its potential relationship with clinicopathological parameters and survival. Stat3 expression was studied by immunohistochemistry. Cytoplasmic or nuclear localization of Stat3 was observed in 62% of patients, whereas only nuclear Stat3 expression was found in 44%. Stat3 positivity in early-stage patients was 45% compared to 79% in advanced-stage patients. However, early-stage Stat3-positive patients showed a gradual increase in staining intensity, with intense staining seen in 52% of the tumors compared to 18% in Stat3-positive advanced-stage patients, where a gradual decrease in intensity expression was observed (p=0.001). Stat3 showed a significant positive correlation with disease stage (p=0.001), nodal status (p=0.033) and tumor size (p=0.001). Multivariate survival analysis using the Cox proportional hazard regression model showed that nuclear Stat3 was a significant independent prognosticator for both relapse-free survival (p=0.014) and overall survival (p=0.042) in early-stage patients. Our results indicated that Stat3 activation is an early event in oral squamous cell carcinoma and represents a potential risk factor for poor prognosis in early-stage patients.
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