Materials and Methods: In this study, 545 pleural fluid aspiration materials that resulted as Bolu Abant İzzet Baysal University İzzet Baysal Training and Research Hospital between 2014 and 2020 were evaluated retrospectively. The evaluation results were divided into four groups as inconclusive, negative for malignancy, suspected malignancy, and malignant cytology. The biopsy diagnoses of 64 cases were grouped as inadequate, benign, and malignant. Sensitivity and specificity values were calculated by looking at the relationship between cytology and biopsy diagnoses.

Results: According to the cytology diagnoses, 435 cases (79.8%) were negative for malignancy, 43 cases (7.9%) were malignant, 32 cases (5.9%) were suspected of malignancy, and 35 cases (6.4%) were inconclusive. When the diagnoses of the cases with both cytology and biopsy analyses were compared, the sensitivity of the cytology was 96.7%, the specificity was 91.2%, the positive predictive value was 90.6%, and the negative predictive value was 96.7%. The biopsy and cytology results were found to be compatible (p < 0.05)

Conclusions: Pleural effusion develops due to different etiologies, and the cytological examination of pleural fluid is an important diagnostic method for malignancy. In our region, the most common cause of pleural effusion is benign pathologies which are consistent with data in the literature. The correlations between cytology- and biopsy-based diagnosis results were found high. Keywords : Pleural effusion, malignancy, pleural effusion cytology, pathology, retrospective