Radiological Red Flags of Triple Negative Breast Cancer on Mammography and Ultrasonography: A Case-control Study

Introduction: Breast cancer is the most common cause of cancer related mortality in Indian women. Aim: To evaluate the imaging characters of Triple Negative Breast Cancer (TNBC) on Mammography and Ultrasonography (USG), with the major goal of identifying imaging predictors of TNBC. Materials and Methods: The present retrospective case-control study was conducted at AIIMS, Rishikesh, Uttarakhand, India, over a period of one year from September 2018 to August 2019. The imaging findings of 50 cases of histopathologically proven TNBC were retrospectively evaluated by two breast radiologists. This was compared with 50 age matched blindly chosen cases of non-TNBC. The statistically significant imaging characters of TNBC were identified by Chi-square test. The imaging predictors of TNBC were identified by regression analysis. Results: The most common mammographic presentation of TNBC was mass without calcification (64%) with round/oval shape (54%) and lobulated margins (38%). The most common ultrasonographic presentation was hypoechoic mass (76%) with round/oval shape (52%) and lobulated margins (44%) with Posterior Acoustic Enhancement (PAE) (54%). PAE (p<0.0001: Area Under Curve (AUC): 0.6200) on USG was the single strongest imaging predictor of TNBC, followed by lobulated margins on mammography (p<0.001: AUC: 0.6300). On multivariate analysis, a lobulated, hypoechoic mass with PAE was found to be the most statistically confident predictor of TNBC on imaging. Conclusion: TNBC has specific imaging features on both mammography and USG which may be used as utility tools in early diagnosis. A round, lobulated mass on both modalities with hypoechogenicity and PAE on USG are definite red flags for TNBC on imaging.