What is the significance of non-specific pleuritis? A trick question

Non-specific pleuritis (NSP) is defined as fibrinous or inflammatory pleuritis which cannot be attributed to a specific benign or malignant etiology. It can be diagnosed in biopsies in up to 30% of cases of exudative pleuritis after thoracoscopy, with a mean of 19.2%. In 66 out of 469 (14.2%) patients in combined series, a malignant pleural disease (mostly mesothelioma) was found during a follow-up of at least 21 months. Most likely, a follow-up time of 12 months is sufficient, although the current routine is a follow-up of 2 years. Because of a benign course in 85% of patients with NSP, a repeated invasive procedure after thoracoscopy is only indicated in a limited group of patients. The most important indications for a repeated pleural biopsy are persistent chest pain, recurrent pleural effusion, radiologic findings suggestive for malignant pleural disease.