Ascitic fluid cell block with immunocytochemistry for the diagnosis of advanced tubo-ovarian cancer: a retrospective study

Abstract Background Differentiating advanced tubo-ovarian cancer from other malignancies in patients presenting with ascites and pelvic masses remains a critical clinical challenge. While liquid-based cytology (LBC) and serum tumor markers such as CA125 and CEA are commonly used, their diagnostic accuracy is limited. Ascitic fluid cell block (ACB) combined with immunocytochemistry (ICC) has emerged as a promising alternative, yet its comparative performance against conventional approaches—including LBC and the CA125/CEA ratio—has not been systematically evaluated in large cohorts. Methods In this retrospective study, we compared the diagnostic performance of four strategies: LBC alone, a CA125/CEA ratio > 25, LBC combined with CA125/CEA ratio > 25, and ACB combined with ICC. All methods were evaluated against histopathological findings from surgical or biopsy specimens as the reference standard. Analyses included patients with confirmed malignant ascites; a subset with complete ascitic fluid testing data was used for the primary evaluation of ACB combined with ICC. Results ACB combined with ICC demonstrated almost perfect agreement with histopathology (Cohen’s κ = 0.90). This method achieved 100% sensitivity, 81.8% specificity, a 99.2% positive predictive value, a 100% negative predictive value, and an overall diagnostic accuracy of 99.2%. Receiver operating characteristic analysis confirmed that ACB combined with ICC had significantly superior discriminative ability compared to all other evaluated methods (all P < 0.001). Conclusion ACB combined with ICC shows near-perfect concordance with histopathological diagnosis (HIS) and exceptional diagnostic accuracy for identifying tubo-ovarian carcinoma. These results support its role as a reliable pre-treatment diagnostic tool, particularly in clinical scenarios where tissue confirmation is delayed or contraindicated, and when timely decisions regarding neoadjuvant chemotherapy are required.