Improvement of malignant serous effusions diagnosis by quantitative analysis of molecular claudin 4 expression

Claudin gene expression is frequently altered in human cancers. Our aim was to improve the cytology diagnosis of malignancy in serous fluids with the quantification of claudins compared with various classic molecular markers using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) method. Peritoneal or pleural effusions of 56 patients were assessed as malignant from histological analysis and 19 as benign. Claudin 4 was the most significantly upregulated (68%) marker in patients with malignant effusions. In cytologically negative malignant effusions, claudin 4 was found increased in 8/18 fluids. Quantitative RT-PCR is a sensitive method for the detection of free cancer cells in serous effusions.