Different characteristics of pleural abnormalities on computed tomography between tuberculous and malignant pleural effusions

Background: Computed tomography (CT) is the mainstay imaging modality for suspected pleural malignancy. Tuberculous pleural effusion (TPE) can present with various pleural abnormalities. However, few studies have evaluated the different characteristics of pleural abnormalities on chest CT between TPE and malignant pleural effusion (MPE). Methods: Pleural abnormalities on contrast-enhanced CT in 277 and 289 patients with confirmed TPE and MPE diagnoses, respectively, were retrospectively assessed and compared between the two groups. Discriminating factors and diagnostic performance for MPE were evaluated using multivariate analysis and receiver operating characteristic curves. Results: Focal pleural thickening was present in 44 (16%) cases of TPEs and 202 (70%) of MPEs. Further characterization of focal pleural thickening showed that MPEs had a significantly greater number, larger maximal thickness, and more nodular contour form, compared to TPEs. On the other hand, diffuse and circumferential pleural thickening were significantly more common in TPEs. In multivariate analysis, independent predictors for MPE included focally thickened pleurae ≥7, maximum thickness ≥6 mm, nodular contour pattern, and the absence of diffuse pleural thickening. Out of all the individual or combined predictors for MPE, the presence of any one of the three sub-parameters of focal pleural thickening provided the best diagnostic yield with 66% sensitivity and 92% specificity. Conclusion: Although focal pleural thickening in TPE mimics that in MPE, the features of MPE are significantly different from those of TPE in terms of size, number, and contour. These different characteristics may help differentiate MPE from TPE in patients with suspected MPE.