Metastatic Lung Adenocarcinoma Presenting With Cavitary and Consolidative Lung Findings: A Diagnostic Dilemma

<b>Introduction:</b> Lung cancer is the leading cause of cancer-related mortality, with non-small cell lung cancer (NSCLC) accounting for 85% of cases. Lung adenocarcinoma, the most common subtype, can mimic benign conditions like pneumonia, lung abscess, and interstitial lung disease due to its varied radiologic presentations and associated inflammation and fibrosis. This similarity can delay diagnosis, emphasizing the need for imaging and histopathological confirmation. <b>Case Presentation:</b> A 58-year-old male with a significant smoking history, hypertension, and GERD presented with a 5-month history of episodic epigastric pain, exacerbated by heavy meals, along with progressive respiratory symptoms, including shortness of breath, dry cough, and a 20-kg weight loss over 3 months. Upper endoscopy revealed gastric ulcers, a hiatal hernia, esophageal mucosal changes consistent with GERD, and <i>Helicobacter pylori</i> infection on biopsy, which was treated with triple therapy, resolving his gastrointestinal symptoms. However, his respiratory symptoms worsened, with increased dyspnea at rest, pleuritic chest pain, and a persistent cough. Chest CT showed multiple cavitating lung nodules, architectural distortion predominantly in the upper lobes, a large irregular lesion in the right lower lobe, and enlarged paratracheal, subcarinal, and distal paraesophageal lymph nodes. The patient was transferred to our facility for further evaluation. Whole-body CT revealed widespread bilateral cavitary lesions, lymphadenopathy, and a small hiatal hernia. Bronchoscopy with biopsy confirmed metastatic lung adenocarcinoma, with histopathology showing moderately differentiated adenocarcinoma, positive for TTF-1 and Napsin A and negative for PAX8. Cytology from bronchoalveolar lavage also confirmed malignancy, and PD-L1 immunostaining showed weak positivity in 15%-20% of tumor cells. The patient was diagnosed with metastatic lung adenocarcinoma and initiated on carboplatin and pemetrexed chemotherapy. Molecular testing was planned, and he was discharged for follow-up care. <b>Conclusion:</b> Our case of a 58-year-old male with cavitating lung nodules, significant weight loss, and progressive respiratory symptoms, initially misattributed to gastrointestinal disease, highlights the diagnostic complexity of lung adenocarcinoma. The biopsy-confirmed diagnosis of metastatic adenocarcinoma underscores the need for clinicians to maintain a high index of suspicion for malignancy in patients with atypical or nonspecific presentations. Early tissue diagnosis is crucial for timely treatment and improved outcomes, especially in cases involving cavitary lesions or persistent, unexplained symptoms.