The use of immunocytochemistry to diagnose the etiology of malignant pleural effusion.

The appearance of malignant pleural effusion (PE) is often the first and only symptom of a malignant tumor (MT). In these conditions, the morphological verification of cancer is important for the planning of systemic antitumor treatment. Aims and Objectives: to determine the potential of immunocytochemical methods in the differential diagnosis of malignant PE. Methods: during the period from 2012 to 2017, we observed 234 patients with malignant PE and MT with unknown primary tumor site. All patients underwent a cytomorphological examination of the PE during the diagnosis. 81 patients in thoracic surgery depatment underwent videothorascopy (VTS) with biopsy of the parietal pleura. 93 patients (54 - outpatients) underwent transthoracic needle biopsy of the parietal pleura. On 60 patients (55 - outpatients), an immunocytochemical study of PE was performed. The sensitivity, specificity of the diagnosis in the groups and also its accuracy were assessed. Results: cytomorphological examination of PE was not sufficiently effective. Triplicate cytologic examination detected tumor cells in 76% of cases. Only 16% were able to determine the primary site of the MT. The most effective method was VTS with pleural biopsy: sensitivity 98%, specificity 99%, accuracy 99%. Transthoracic biopsy of the pleura using the Abrams needle showed significantly less diagnostic value: sensitivity 68%, specificity 73%, accuracy 70%. The immunocytochemical method was not inferior to VTS in detecting the primary tumor site: 95% sensitivity, specificity 99,6%, accuracy 95%. Conclusion: an immunocytochemical study is a reliable tool in the diagnosis of malignant PE, and can be succcessfully used in outpatient settings.