: This study aims to evaluate the mRNA expression of cyclooxygenase-2 (Cox-2) in ascites caused by various diseases and its usefulness in differential diagnosis between malignant and benign ascites.

A total of 52 ascitic fluid samples collected from patients in Ghaem Hospital of Mashhad University of Medical Sciences and divided into two experimental groups: benign ascites group (n=26) and malignant ascites group (n=26). Reverse transcriptase polymerase chain reaction (RT- PCR) was used for determining the presence of Cox-2 mRNA in samples.

There was a mail predominance (1.88 to 1) and the mean age of patients was 56.94±12.04 years (range 30 to 80 years). There was no significant difference between the two groups with respect to age and sex. Cox-2 mRNA was detected in 4 of 26 benign ascites (15.4%) and 15 of 26 malignant ascites (57.7%) (P= 0.003). The sensitivity, specificity, positive and negative predictive values of Cox2 for differentiating malignant from benign ascites were 57.7%, 84.6%, 78.9% and 66.7%, respectively.

: Cox2 mRNA expression assessed by RT-PCR could be a useful method in the differential diagnosis and screening of malignant ascites.