Non-Specific Pleuritis After Medical Thoracoscopy: The Portrait of an Open Issue and Practical Hints for Its Management

<b>Background/Objectives:</b> Up to one third of pleural biopsies performed during medical thoracoscopy (MT) are labelled as non-specific pleuritis (NSP). The histological diagnosis of NSP has long been worrisome for pulmonologists, with the potential to evolve into a life-threatening condition. The aim of this study was to identify clinical and biological predictors for patients with a diagnosis of NSP to guide clinical decisions. <b>Methods</b>: Baseline, procedural and follow-up data of NSP patients were retrospectively analysed to identify potential outcome predictors. <b>Results</b>: Of the 272 patients who underwent MT, 192 (71%) were diagnosed with malignancies, 9 (3%) with benign diseases and 71 (26%) with NSP. At follow-up, 17% were diagnosed with malignant disease and 21% with a benign condition and 62% remained idiopathic. A thoracoscopist's evaluation of the pleural appearance reported a PPV of 28% and an NPV of 91% to predict malignancy. Patients with a subsequent diagnosis of malignancy tended to have a higher volume of fluid drained than those with persistently idiopathic NSP [2.7 litres (L) vs. 1.6 L <i>p</i> = 0.06]. A lymphocytic pleural effusion was more common in the malignant and idiopathic groups (63% and 60%, respectively) than the benign group (16%; <i>p</i> = 0.06 and <i>p</i> = 0.01). The three groups had a similar rate of effusion recurrence. Overall survival was higher in patients with idiopathic pleural effusion than in those with malignant (<i>p</i> = 0.04) or benign disease (<i>p</i> = 0.008). <b>Conclusions</b>: NSP diagnosis hides a malignancy in one in five cases, underlying the importance of closely following up these patients. The volume of drained pleural fluid, cell count and thoracoscopist's impression may guide clinicians in the challenging management of patients with NSP.