Diagnostic benefits of the combined use of liquid-based cytology, cell block, and carcinoembryonic antigen immunocytochemistry in malignant pleural effusion

Background: Malignant pleural effusion (MPE) is a common complication of cancer cell metastasis to the pleura. Discrimination between MPE and benign pleural effusion is necessary to design treatment strategies. Cytology is important for the diagnosis of MPE. Carcinoembryonic antigen (CEA) is an epithelial biomarker with a strong staining pattern in adenocarcinomas. Here, the diagnostic performances of liquid-based cytology (LBC), cell block (CB) preparation, and CEA immunostaining for the detection of malignancy in effusion cytology were compared in a large case series. Methods: In a single institution, 1,014 cytology samples from 862 patients were retrospectively collected and reviewed between January 2013 and November 2015. Ethanol-fixed, paraffin embedded CB of pleural effusions was analyzed by CEA immunostaining. Diagnostic values were compared among LBC, CB, CEA immunostaining, and the combination of two methods. Results: The sensitivity and specificity of the CB preparation were 94.3% and 98.7%, respectively, compared with 81.3% and 99.4% for LBC preparations, respectively. Combination of LBC and CB increased sensitivity by 98.3%. Although the accuracy of CEA staining itself was moderate (sensitivity, 89.8%), the combined use of CB and CEA tumor marker increased the detection rate of malignancy (sensitivity, 100%; specificity, 100%), compared with that of cytology (LBC or CB) alone. Conclusions: The sensitivity and specificity for the diagnosis of MPE could be improved by integrating the CB and CEA staining into LBC in routine clinical practice to improve diagnostic accuracy.