OBJECTIVE: To analyze the diagnostic and prognostic value of CASC5 in lung adenocarcinoma. STUDY DESIGN: The expression of CASC5 in clinical specimens was evaluated by bioinformatics analyses and immunohistochemistry. RESULTS: Bioinformatics analyses relying on The Cancer Genome Atlas (TCGA) database suggested the increased CASC5 mRNA levels in lung adenocarcinoma and the involvement of CASC5 in cell cycle regulation. Moreover, CASC5 mRNA levels were positively correlated with the American Joint Committee on Cancer (AJCC) stage and with poor patient survival. Consistent with the TCGA mining results, immunohistochemistry demonstrated that CASC5 protein levels were upregulated in lung adenocarcinoma in comparison to noncancerous tissues and were positively associated with T classification and PDL1 expression. Moreover, CASC5 expression predicted a poor outcome in lung adenocarcinoma patients. CONCLUSION: Our study demonstrated that CASC5 enhanced lung adenocarcinoma progression and was identified as an independent prognostic indicator for lung adenocarcinoma. © Science Printers and Publishers, Inc.