Endobronchial Ultrasound-guided Diagnosis of Occult Lung Adenocarcinoma with Normal Chest Radiograph

ABSTRACT: Lung adenocarcinoma is the most common histological subtype of lung cancer and typically presents as a peripheral lesion detectable on routine imaging. However, atypical presentations with normal chest radiographs may pose significant diagnostic challenges and delay definitive management. Advanced diagnostic modalities such as high-resolution computed tomography (HRCT), positron emission tomography computed tomography (PET-CT), and endobronchial ultrasound (EBUS) have improved the detection of occult malignancies. We report a case of a 59-year-old female presenting with cough, hemoptysis, and dyspnea. Initial chest radiography was unremarkable despite persistent symptoms. HRCT thorax revealed an abrupt cutoff of the left lower lobe bronchus with distal collapse, raising suspicion of an endobronchial lesion. Bronchoscopy with bronchoalveolar lavage was inconclusive. PET-CT demonstrated a metabolically active mass in the left lower lobe without nodal involvement. EBUS-guided fine-needle biopsy confirmed lung adenocarcinoma, with immunohistochemistry positive for thyroid transcription factor-1. The patient was staged as Stage IIB lung cancer and was planned for neoadjuvant chemotherapy followed by surgical intervention. The case highlights the diagnostic superiority of EBUS in evaluating radiologically occult malignancies. Normal chest radiographs do not exclude significant pulmonary pathology. A systematic diagnostic approach incorporating advanced imaging and minimally invasive tissue sampling techniques, such as EBUS, is crucial for early detection and improved outcomes in lung cancer.