High level of ezrin mRNA expression in an osteosarcoma biopsy sample with lung metastasis. Osteosarcoma (OS) remains a life-threatening malignancy and its molecular character is not fully understood. Ezrin is a cytoskeleton linker protein involved in regulating the growth and metastatic capacity of cancer cells. However, the correlation between ezrin mRNA expression and clinical severity has not yet been examined in OS biopsy samples. Furthermore, recent evidence has demonstrated that the level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression is increased in human cancers of various origins, but this has not yet been examined in OS cells. To clarify the correlation between the clinical severity and the levels of ezrin and GAPDH mRNA expression, we quantified these mRNA levels in 4 pediatric OS biopsy samples using real-time quantitative polymerase chain reaction. Among these 4 samples, ezrin mRNA expression was approximately 5-fold higher in a case with lung metastasis compared with the other cases without metastasis, suggesting an association between the ezrin mRNA expression level and metastasis. On the other hand, the GAPDH mRNA expression level was not related to the clinical severity. This is the first report to demonstrate a high level of ezrin mRNA expression in an OS biopsy sample with lung metastasis.