The comparative accuracy of ultrasound and mammography in the detection of breast cancer

AIM: This study was performed to determine the accuracy of ultrasound (USG) as compared to mammography (MMG) in detecting breast cancer.

METHODS: This was a review of patients who had breast imaging and biopsy during an 18-month period. Details of patients who underwent breast biopsy were obtained from the department biopsy record books and imaging request forms. Details of breast imaging findings and histology of lesions biopsied were obtained from the hospital Integrated Radiology Information System (IRIS). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of USG and MMG were calculated with histology as the gold standard.

RESULTS: A total of 326 breast lesions were biopsied. Histology results revealed the presence of 74 breast cancers and 252 benign lesions. USG had a sensitivity of 82%, specificity of 84%, PPV = 60%, NPV = 94% and an accuracy of 84%. MMG had a sensitivity of 49%, specificity of 89%, PPV = 53%, NPV = 88% and an accuracy of 81%. A total of 161 lesions which were imaged with both modalities were analyzed to determine the significance in the differences in sensitivity and specificity between USG and MMG. Sensitivity of USG (75%) was significantly higher than sensitivity of MMG (44%) (X(2)1=6.905, p=0.014). Specificity of MMG (91%) was significantly higher than specificity of USG (79%) (X(2)1=27.114, p<0.001). Compared with MMG, the sensitivity of USG was 50% (95% CI 10%-90%) higher in women aged less than 50 years (X(2)1=0.000, p=1.000) and 27% (95% CI 19%-36%) higher in women aged 50 years and above (X(2)1=5.866, p=0.015). Compared with MMG, the sensitivity of USG was 40% (95% CI 10%-70%) higher in women with dense breasts (X(2)1=0.234, p=0.628) and 27% (95% CI 9%-46%) higher in women with non-dense breasts (X(2)1=4.585, p=0.032).

CONCLUSION: Accuracy of USG was higher compared with MMG. USG was more sensitive than MMG regardless of age group. However, MMG was more specific in those aged 50 years and older. USG was more sensitive and MMG was more specific regardless of breast density. In this study, 20% of breast cancers detected were occult on MMG and seen only on USG.