Endobronchial ultrasound (EBUS) bronchoscopy is commonly used to sample lymph nodes in patients with suspected or known lung cancer to determine the stage of the disease. Accurate staging is essential as it directly impacts treatment decisions and prognosis. During EBUS procedures, needles are often reused across multiple lymph node stations and are typically flushed with saline between samples. This raises the concern that residual tumor cells may contaminate the samples and could potentially incorrectly upstage disease.

This prospective study will evaluate the current technique used during EBUS procedures to determine if more intensive cleaning leads to reduced cellular contamination without affecting diagnostics. Patients undergoing an EBUS procedure for diagnosis with a large mass and a high probability of malignancy will be selected for the study. Rapid On-Site Examination (ROSE) will be used at the bedside to determine the presence of abnormal cells. Following the final pass, before moving to the next station, the needle will be flushed with saline as normal and then flushed again into another container to evaluate the presence of residual cells. The outcome may help EBUS needle handling practices and improve lung cancer staging accuracy.

No additional invasive procedures are performed as part of this study; all analyses utilize material obtained during routine EBUS needle flushing, with no added needle sticks or alteration of clinical care.

EBUS guided transbronchial needle aspiration (TBNA) is a cornerstone in lung cancer staging. Accurate nodal staging under the TNM 9th edition guidelines is essential. Prior work has demonstrated that EBUS needle contamination can occur. A prospective multicenter study published in Archivos de Bronconeumologia demonstrates residual malignant cells despite repeated saline flushes with increasing flush volumes. A prospective observational study by Berim et al. showed malignant and non-malignant cellular debris can persist after multiple cleaning steps. Repeated flushing reduced but did not eliminate the contaminants, suggesting the current practice of flushing with saline may be insufficient to prevent contamination. The above studies demonstrate that contamination does exist in EBUS needle aspiration though there is no universal consensus on how to address contamination risk. The proposed project would identify cytologic contamination present in our current practices, without any additional risk from a procedural standpoint to the patient. This project would also examine the presence of malignant cells despite additional flushing.

Inclusion Criteria:

• Adults aged 18 years or older
• Patients undergoing standard-of-care EBUS bronchoscopy for evaluation of suspected lung malignancy
• Patients undergoing sampling of 2 or more lymph node stations during EBUS bronchoscopy
• Ability to provide informed consent

Exclusion Criteria:

• Age less than 18
• Recent (1 month or less) radiation or procedural manipulation of lymph node stations that may significantly change lymph node architecture

Individual participant data, such as age and gender, that are utilized in results for publication will be shared.