Diagnostic Accuracy of Combined Mammography and Ultrasound in the Detection of Malignant Breast Lesions Using Bi-RADS Classification Taking Histopathology as the Gold Standard

Abstract

Introduction: Breast cancer is the leading cause of cancer in women with an estimated 2.3 million new cases worldwide and a high mortality rate. The incidence of breast cancer has been increasing worldwide in the past few years with a similar trend of escalation in Pakistan. The age-standardized incidence rate of breast cancer in Pakistan is 104 per one million and the mortality rate is 65 per one million population. Limited studies have been done to evaluate the diagnostic accuracy of combined mammography and ultrasound with BI-RADS scoring in the detection of breast cancer and positive predictive value of its morphological descriptors in Pakistan. Objective: Our study aims to determine the diagnostic accuracy of combined mammography and ultrasound in the detection of malignant breast lesions using BI-RADS classification taking histopathology as the gold standard and positive predictive value of its morphological descriptors. Materials and Methods: This was a retrospective, cross-sectional analysis. All the patients presented with breast-related symptoms and for screening in whom mammography with complimentary ultrasound was performed were included. Mammography protocol includes image acquisition in craniocaudal and mediolateral oblique views. On ultrasound, all quadrants of the breast, retroaerolar region, and axilla were assessed. Patient stratification was done based on the age, clinical symptoms, and positive malignant lesions on histopathology; and frequency and percentage were calculated. Sensitivity, Specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), and diagnostic accuracy was calculated. PPV of individual morphological descriptors were also calculated. The association of various morphological descriptors with malignancy was analyzed using a chi-square chart. p-value of less than 0.05 was considered significant. Results: In 69 patients with suspicious imaging findings, 89.9% patients presented with breast lumps, 34.8% patients had pain, and 11.6% patients had nipple discharge. 8.7% had nipple retraction and 10.1% had skin changes. 52.2 % patients were post-menopausal and 46.1% patients were premenopausal. On histopathology, 88.4% patients had malignant disease and 11.5% were having benign lesions. The mean age of patients with malignant masses was 50.9 years+13.1 SD. No significant statical difference is noted between younger and older groups. The mean size of the malignant mass was 3.0 cm+1.8 SD. The sensitivity of combined mammogram and ultrasound was calculated to be 98.3%, specificity was 25.0%, PPV was 90.9%, NPV was 66.6% and diagnostic accuracy was 89.9%. Conclusion: We conclude that the combined mammography and ultrasound serve as an important diagnostic tool, both for screening purpose as well as in patients with breast related symptoms for the diagnosis of breast cancer. Moreover, the morphological descriptors of malignancy on mammography and ultrasound as described by BI-RADS lexicon are reliable indicators of malignancy in patients with breast lesions.