Study of risk of malignancy index in the pre-operative evaluation of patients with ovarian tumour

Background: Ovarian tumours present a significant diagnostic challenge because their clinical features often mimic benign conditions, resulting in delayed recognition of malignancy. Early and reliable differentiation between benign and malignant adnexal masses is essential to ensure appropriate referral, optimal surgical planning and improved outcomes. The Risk of Malignancy Index (RMI), which integrates menopausal status, ultrasound characteristics and serum CA-125 levels, is a simple tool designed to enhance pre-operative discrimination.Aim: To evaluate the diagnostic accuracy of the Risk of Malignancy Index at a cut-off value of 100 in distinguishing benign from malignant ovarian tumours and to assess its relationship with clinical, ultrasonographic and biochemical variables.Materials and Methods: This prospective observational study included 150 women presenting with adnexal masses who underwent surgery at a tertiary-care centre between July 2023 and December 2024. All patients received a detailed clinical assessment, ultrasonographic evaluation and serum CA-125 measurement. The RMI was calculated using the RMI-1 formula (RMI = U × M × CA-125). Histopathology served as the reference standard for diagnosis. Statistical analysis included sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and ROC curve construction.Results: Among the 150 women, 83.3% had benign tumours and 16.7% had malignant tumours. Benign lesions, particularly cystadenomas, follicular cysts and dermoid cysts, were more prevalent, while epithelial ovarian carcinoma was the most common malignancy. Malignancy was significantly associated with older age, postmenopausal status, larger tumour size and elevated CA-125 levels. An RMI cut-off of 100 demonstrated a sensitivity of 95.0%, specificity of 92.0%, PPV of 85.7% and NPV of 88.9%. ROC analysis confirmed excellent overall discriminatory performance. Higher RMI categories strongly correlated with malignant histology.Conclusion: The RMI is a reliable, cost-effective and practical tool for pre-operative assessment of ovarian masses. An RMI cut-off of 100 demonstrated high diagnostic accuracy, making it a valuable guide for triaging patients, optimising referral pathways and reducing unnecessary extensive surgery in benign cases. Routine clinical use of the RMI may significantly improve early identification and management of ovarian malignancies.