To assess the performance of conventional ultrasound (US) and contrast-enhanced ultrasonography (CEUS) in the differential diagnosis of focal pleural thickening lesions.

Between January 2016 and December 2021, patients with focal pleural thickening who were referred for surgery or biopsy at Peking University Third Hospital were included. All patients were divided into either a benign group or a malignant group according to the results of pathology and clinical follow-up. The diagnostic results of the two methods and the clinical data of patients in the two groups were compared. Receiver operating characteristics (ROC) curve analysis was performed to calculate the differential diagnosis efficiency of the two methods.

Thirty-six patients were ultimately included. Based on histopathological results, the lesions were classified into two groups: benign (n=18) and malignant lesions (n=18). Age and gender did not differ significantly between the two groups (P＞0.05). The length of pleural thickening lesions in the malignant group was significantly shorter than that in the benign group [(2.65±1.49) cm vs (5.36±2.98) cm, P=0.002]. CEUS results also showed a statistically significant difference (P=0.027) between the two groups: iso-high enhancement mainly occurred in the malignant group (16/18, 88.9%), while low-no enhancement mainly occurred in the benign group (9/18, 50%). The area under the ROC curve (AUC) of the length of pleural thickening was 0.804, and the optimal cut-off value was 4.75. The AUC of iso-high enhancement was 0.694. The AUC of the two indicators (length and enhancement) combined reached up to 0.816. The sensitivity, specificity, and accuracy were 99.4%, 66.7%, and 80.0% respectively, and the Youden index was 1.611.

Using the maximum length of the lesion on US and the degree of enhancement on CEUS, we can effectively distinguish benign and malignant lesions of focal pleural thickening. The combined use of the two methods not only improves the efficiency of diagnosis, but also provides more valuable information for subsequent needle biopsy, clinical diagnosis, and medical treatment.