Introduction:
Non-specific pleuritis (NSP) is a fibrinous or inflammatory pleurisy that is not attributable to a benign or malign etiology. The long-term follow-up results of patients diagnosed with NSP following video- assisted thoracoscopic surgery (VATS) were investigated in this study.

Material and methods:
This investigation focused on 593 patients with exudative pleural effusion who underwent VATS between 2011 and 2014. Of the 137 patients diagnosed with NSP, a total of 39 patients were excluded from the study.

Results:
Out of the 98 patients, 78 were male (80%) with their mean age being 52.2 ±15.9 years. The mean follow-up period was 1919 ±744 days. Of these patients, 70 (71.4%) had no specific diagnosis, while 28 patients (28.6%) did have specific diagnoses. Malignancy was detected in seven (7.1%) of those with specific diagnoses, with most of the diagnoses of malignancy detected within the first 36 months. Malignant diseases included mesothelioma (n = 2), lung cancer (n = 2), chronic lymphocytic leukemia (n = 1), soft tissue sarcoma (n = 1), and multiple myeloma (n = 1). Chest radiographs of malignant patients showed that statistically significantly larger amounts of fluid (40% vs. 6.9%, p = 0.026), pleural plaque (20% vs. 1.1%, p = 0.020) and nodules (20% vs. 7.7%, p = 0.020) were detected compared to patients with a benign course.

Conclusions:
Most patients diagnosed with NSP after VATS had a benign disease course. There was a probability of malignancy, although it was low. Mesothelioma and other malignancies could be seen within the first 36 months after the biopsy. Apart from mesothelioma, other malignancies should also be considered, and further follow-up recommended for patients with a large amount of fluid, plaque and nodules found in the initial VATS images.