Objective Thoracoscopic Criteria in Differentiation between Benign and Malignant Pleural Effusions

Thoracoscopy is the "gold standard" diagnostic modality for investigation of suspected pleural malignancy. It is postulated that meticulous assessment of the pleural cavity may be adequate to indicate malignancy through the macroscopic findings of nodules, pleural thickening, and lymphangitis. We attempted to critically assess this practice, by precisely defining objective macroscopic criteria which might differentiate benign from malignant pleural diseases according to intrapleural pattern and anatomical location, and thereby to explore the predilection of abnormalities to specific sites on pleural surfaces.

A structured review of recorded video footage from medical thoracoscopy procedures in 96 patients was conducted by 2 independent assessors. Abnormalities were scored on agreed, objective criteria for the presence of nodules, lymphangitis and inflammation on each of the costoparietal, visceral and diaphragmatic surfaces. The costoparietal pleura was divided into 6 levels (apical, middle, and inferior surfaces of the lateral and posterior parietal pleura). The anterior surface of the costoparietal pleura was excluded from analysis after interim review as this surface was rarely seen.

In the benign group, inflammation was the predominant finding in 65% (n = 33; costoparietal), 44% (n = 21; visceral), and 42% (n = 15; diaphragmatic). Nodules were detected in 24% (n = 12; costoparietal), 8% (n = 4; visceral), and 8% (n = 3; diaphragmatic). The most affected surfaces with inflammation were the middle lateral (60%) and the inferior lateral (57.8%) parts of the costoparietal pleura. In the malignant group, nodules were the predominant finding according to surface in 73% (n = 33; costoparietal), 32% (n = 13; visceral) and 48% (n = 17; diaphragmatic). Inflammation was detected in 44% (n = 20; costoparietal), 25% (n = 10; visceral), and 29% (n = 10; diaphragmatic). The most affected surfaces with nodules were the middle lateral (67.4%) and inferior lateral (66.7%) costoparietal pleural surfaces.

This is the first detailed, anatomical description of abnormalities in the pleural space during thoracoscopy. While nodules were the predominant pattern in malignant pleural effusion, they were detected in 24% of benign diagnoses. Detection of nodules in >1 area of the costoparietal pleura was in favor of a malignant diagnosis. Inflammation was the predominant pattern in benign pleural effusion. Our results suggest that macroscopic nodules in malignant diagnoses have a predilection for the middle and inferior surfaces of the lateral costoparietal pleura.