Abstract Background Malignant pleural mesothelioma (MPM) is an aggressive neoplasm originating from mesothelial cells, most commonly associated with asbestos exposure. Diagnosis often begins with imaging and pleural fluid analysis, followed by pleuroscopy or surgical biopsy. However, diagnostic yield can be limited by tumor location especially when lesions are medial, diaphragmatic, or posterior, and thus not easily accessed by pleuroscopy. In such cases,surgical approaches like video-assisted thoracoscopic surgery play a critical role in obtaining a definitive diagnosis. Case Presentation A 70-year-old man with a significant history of asbestos exposure presented with progressive dyspnea, leftsided chest discomfort, and unintentional weight loss. Imaging revealed a large left pleural effusion with near-complete lung collapse, bilateral pleural plaques, and focal FDG uptake along the medial pleura on PET-CT. Pleuralfluid analysis showed an exudative effusion (protein 5.3 g/dL, LDH 351 U/L, glucose 89 mg/dL) with 78% lymphocytes, but cytology was non-diagnostic for malignancy. Due to the medial lesion’s poor accessibility by pleuroscopy, video-assisted thoracoscopic surgery was performed, revealing a firm mass along the inferior pulmonary ligament. Biopsy confirmed epithelioid malignant pleural mesothelioma, positive for calretinin, WT-1, and D2-40, with BAP1 loss. Patient declined extrapleural pneumonectomy and opted for systemic chemotherapy and radiation. Discussion This case highlights the diagnostic challenges posed by MPM, particularly when lesions are located in regions inaccessible to routine diagnostics such as pleural fluid analysis and pleuroscopy. Pleural fluid cytology has a diagnostic yield of approximately 30-60% in mesothelioma, and pleuroscopy increases that yield to 90%, provided the lesion is visible and accessible.The inferior pulmonary ligament, a pleural reflection anchoring the lower lobe of the lung, is not typically visible during single-port pleuroscopy, limiting biopsy in that region. In our patient, PET-CT imaging was instrumental in identifying metabolically active pleural disease that could not be accessed via pleuroscopy, thus prompting a shift to VATS. Several studies have emphasized the importance of early surgical referral when imaging suggests atypical pleural thickening or medial pleural masses. VATS not only facilitates full visualization of the pleura but also allows for definitive tissue sampling, critical for early diagnosis and timely oncologic management. This case emphasizes the diagnostic limitations of cytology and pleuroscopy when evaluating medially located pleural lesions such as those involving the inferior pulmonary ligament. VATS should be considered early in patients with inaccessible pleural lesions, especially when imaging suggests possible malignancy. Prompt diagnosis can lead to timely initiation of treatment and improved outcomes in malignant pleural mesothelioma. This abstract is funded by: None
Parchuri et al. (Fri,) studied this question.