A 2‐year retrospective study on pleural effusions: A cancer centre experience

Background Cytopathological examination of pleural effusions is a fast and minimally invasive method for verification of the presence of neoplastic cells. We report our 2‐year experience using a categorised diagnostic system and reporting risks of malignancy (ROMs) for each defined category. Methods Cytological reports of patients between November 2016 and October 2018 were collected, with results primarily classified into a five‐tiered classification scheme. Immunohistochemistry markers used in cytology and their results were also recorded. Final agreement to histology and overall test performance was calculated for cases with available concomitant (up to 3 months) pleural biopsies. Results A total of 519 samples from 385 patients were collected, being 29 (5.6%) classified as non‐diagnostic, 291 (56%) as negative, 28 (5.4%) as atypical, 30 (5.8%) as suspicious and 141 (27.2%) as positive. Most requested markers were calretinin, TTF1, Ber‐EP4 and Gata‐3, being conclusive in 45 (76.3%) cases. Total cyto‐histological agreement was achieved in 49 (80.3%) specimens, with an overall sensitivity and specificity of 69.4% and 93.3%, respectively. Positive predictive value was 96.2% and negative predictive value was of 56%. ROM for each diagnostic category was 50% for non‐diagnostic, 44% for negative, 50% for atypical, 83.3% for suspicious and 96.2% for positive. Conclusions Our 2‐year retrospective study has shown a high specificity and positive predictive value for pleural cytology. The use of a five‐tiered system has also shown to be highly effective, with a concordantly progressive higher ROM for the assigned diagnostic categories. Our 2‐year retrospective study on pleural effusions has shown a high specificity and PPV for cytology, being an excellent test for rapid analysis of effusions. The use of a five‐tiered system has also shown to be effective, with a progressively higher risk of malignancies (ROM) for diagnostic categories. To the best of our knowledge, this is the first retrospective study on pleural effusions reporting ROM for assigned diagnostic categories. This study could serve as a first report of many studies handling such important issue, and helping support the development of the upcoming International System for Reporting Serous Fluid Cytopathology.