The goal of this multicenter observational study is to evaluate the lung cancer diagnostic value of epigenetic imprinting detection in bronchoalveolar lavage. This study will mainly focus on varifing the previously identified epigenetic imprinting biomarkers for lung cancer and upgrading and validating a lung cancer imprinting diagnostic model specifically for bronchoalveolar lavage. The lavage sample will be collected from each eligible paticipants under bronchialscopy and undergo QCIGISH detection to analyze the allelic expression status of imprinted genes. The QCIGISH detection results will be compared with the final surgical histopathology. No interventions will be taken according to the QCIGISH detection results.

Bronchial biopsy and bursh are widely used in lung cancer diagnosis but not bronchoalveolar lavage because of its low sensitivity. As the molecular alterations usually occur before the morphological changes, genetic and epigenetic biomarkers will be helpful for early diagnosis of cancers. As an important epigenetic regulation in mammalian embryo development, genomic imprinting plays important roles in cancers. In normal post-natal somatic cells, imprinted genes are "silenced", that is mono-allelically expressed either from the maternal or paternal allele, while in cancers, some silenced imprinting genes' copies could be reactivated, leading to expressions from both alleles. The loss of monoallelic gene regulation is named loss of imprinting (LOI), and has been previously found in various human cancers. Our previous studies has identified several imprinted genes with elevated aberrant allelic expressions in lung cancer. A diagnostic model based on the epigenetic imprinting biomarkers achieved 99.1% sensitivity and 92.1% specificity. In this study, we will first verify the epigenetic imprinting biomarkers in bronchoalveolar lavage, and refine the previously developed diagnostic model specifically for lavage samples. The diagnostic model will be independently validated in a group of prospectively enrolled cases. This study will help to distinguish benign and malignant pulmonary nodules presurgically, and improve the early diagnosis of lung cancer.

Inclusion Criteria:

• Age ≥ 18 years old, and ≤ 75 years old;
• Chest CT showed pulmonary nodule with diameter<3cm;
• Subjects voluntarily participated and signed the informed consent form.

Exclusion Criteria:

• Active massive hemoptysis;
• Severe heart and lung dysfunction;
• Severe arrhythmia;
• Extreme exhaustion of general condition;
• Coagulation dysfunction;
• Acute attack of asthma;
• Aortic aneurysm.

Patients with pulmonary nodules and meet the criteria of bronchoscopy examination