Purpose: Moesin is a linking protein of the submembraneous cytoskeleton and plays a key role in the control of cell morphology, adhesion, and motility. The aim of the present study was to elucidate the clinical significance of expression patterns of moesin in patients with oral squamous cell carcinoma (OSCC). Experimental Design: Immunohistochemistry for moesin monoclonal antibody was performed on 103 paraffinembedded specimens from patients with primary OSCC, including 30 patients with locoregional lymph node metastasis, and in the sections from nude mice transplanted with two cell lines derived from a single human tongue cancer (SQUU-A and SQUU-B). Results: Expression patterns of moesin in OSCCs were divided into three groups: membranous pattern
mixed pattern
and cytoplasmic pattern. These expression patterns correlated with tumor size, lymph node metastasis, mode of invasion, differentiation, and lymphocytic infiltration. In about two-thirds of the patients with metastatic lymph node, homogeneous cytoplasmic expression was detected in the metastatic lymph nodes. In addition, SQUU-B with high metastatic potential showed more reduced levels of membrane-bound moesin than SQUU-A with low metastatic potential. A multivariate analysis demonstrated that expression patterns of moesin can be an independent prognostic factor. Conclusions: Our results suggest that moesin expression contributed to discriminating between patients with the potentiality for locoregional lymph node metastasis and those with a better prognosis and might improve the definition of suitable therapy for each.