The Role of Contrast-Enhanced Ultrasound in the Differential Diagnosis of Malignant and Benign Subpleural Lung Lesions

Background: The application of transthoracic contrast-enhanced ultrasound (CEUS) to the study of peripheral lung lesions is still a topic of debate. The main objective of this review was to evaluate the diagnostic accuracy of CEUS in the diagnosis of malignant subpleural pulmonary consolidations and, therefore, differentiate them from benign ones. Methods: Papers published before December 2023 were detected through a search of PubMed, Cochrane library, and Embase. The pooled specificity and sensitivity, summary receiver operating characteristic (SROC) curve and diagnostic odds ratio (DOR) were used. Results: CEUS is characterized by a pooled sensitivity of 0.95 (95% CI: 0.93-0.97) and a pooled specificity of 0.93 (95% CI: 0.90-0.95) in differentiating benign and malignant subpleural lung diseases; the AUC of SROC was 0.97. Homogeneous CE was characterized by a pooled sensitivity of 0.43 (95% CI: 0.40-0.45) and the pooled specificity of 0.49 (95% CI: 0.46-0.52). Non-homogeneous CE displayed a pooled sensitivity of 0.57 (95% CI: 0.55-0.60) and a pooled specificity of 0.51 (95% CI: 0.48-0.54). The lack of CE displayed a pooled sensitivity of 0.01 (95% CI: 0.00-0.06) and a pooled specificity of 0.76 (95% CI: 0.64-0.85). Marked CE displayed a pooled sensitivity of 0.41 (95% CI: 0.37-0.44) and a pooled specificity of 0.54 (95% CI: 0.50-0.58). Non-marked CE displayed a pooled sensitivity of 0.59 (95% CI: 0.56-0.63) and a pooled specificity of 0.46 (95% CI: 0.42-0.50). The early AT displayed a pooled sensitivity of 0.04 (95% CI: 0.02-0.08) and a pooled specificity of 0.83 (95% CI: 0.77-0.87). The early wash out displayed a pooled sensitivity of 0.61 (95% CI: 0.48-0.72) and a pooled specificity of 0.98 (95% CI: 0.92-1.00). The delayed wash out displayed a pooled sensitivity of 0.15 (95% CI: 0.10-0.20) and a pooled specificity of 0.69 (95% CI: 0.62-0.75). Conclusions: CEUS is characterized by excellent diagnostic accuracy for the diagnosis of the malignancy of subpleural lung lesions. By separately analyzing the CEUS findings, the diagnostic accuracy values are considerably lower and not significant in some cases. The simultaneous evaluation of multiple CEUS features allows us to reach an excellent diagnostic accuracy. Non-homogeneous CE with early wash out are the most indicative features of malignancy of a lung lesion.