Introduction:
Malignant pleural effusion (MPE) is a frequent complication of many malignancies, with lung cancer being the most frequent etiology. Non-small cell lung cancer (NSCLC) is the most prevalent type and accounts for 85% of lung cancer cases. The presence of MPE in NSCLCpatients denotes an end-stage disease with reduced overall survival.Pleural biopsy remains the gold standard diagnostic tool. However, it's considered invasive.Consequently, it's important to identify a pleural fluid biomarker for NSCLC diagnosis. Epigenetic disruptions were linked to NSCLC via oncogene activation or tumor suppressor gene silencing. Circ RNAshave emerged as a class of non-coding RNAs (ncRNAs), which are known as epigenetic modifiers. Circ RNAsare covalently closed loop structure confers them the resistance to RNasescompared to linear RNAs. They are abundantly expressed, withtissue specific patterns. They play role in tumor progression through different regulatory mechanisms such as miRNAs sponging activity and circRNA protein interactions.hsa_circ_0067705 a novel circRNA was found to be up regulated in NSCLC-MPE patients. Thus, it might be involved in NSCLC progression, however, the detailed mechanism and the expression pattern in NSCLC-MPE remainelusive.