Lung Ultrasound for Pleural Effusion in Cancer Patients: Advanced Ultrasound for Pleural Lesions—A Narrative Review

<b>Background:</b> Pleural effusion (PE) is a frequent complication in patients with malignancies and is often associated with poor prognosis. Lung ultrasound (LUS) has become an indispensable bedside tool for detecting, characterizing, and guiding the management of pleural effusions. <b>Methods:</b> This narrative review summarizes the current evidence on the diagnostic performance of LUS for PE in cancer patients, emphasizing recent advances in functional ultrasound techniques. <b>Results:</b> B-mode LUS can detect small-volume effusions and estimate their volume. Sonographic features such as echogenicity, septations, and pleural abnormalities can help differentiate transudative from exudative effusions. Shear-wave elastography and contrast-enhanced ultrasound provide additional functional information on tissue stiffness and perfusion. This information may help distinguish between malignant and benign pleural lesions and facilitate targeted biopsy when cytology is nondiagnostic. Compared with computed tomography, LUS offers superior evaluation of juxtadiaphragmatic and pleural surface abnormalities. It facilitates safe, real-time thoracocentesis. Recent innovations, including improved quality, affordable handheld ultrasound systems and artificial intelligence-based analysis, are expected to further enhance diagnostic precision and accessibility. <b>Conclusions:</b> Although LUS is a sensitive and versatile tool for assessing PE in cancer patients, it has limited diagnostic accuracy in distinguishing between benign and malignant effusions. Advanced techniques, such as shear-wave elastography and contrast-enhanced ultrasound, may further support the differentiation of malignant and benign diseases. Ongoing technological advances are likely to enhance the diagnostic accuracy and accessibility of lung ultrasound.