Objectives: The standard of care for imaging of breast pathology has historically been mammography and sonography. MRI is a modern addition and adjunct in the assessment of breast disease. Some studies have shown that MRI more closely predicts tumor size while others have shown ultrasound to be more accurate than mammography, MRI or physical exam. We looked to examine the differences in imaging modalities and their ability to predict the size in relation to the pathologic size after excision with focus on pathologic subtypes.
Methods: We analyzed patient records across a 4-year period from 2017-2021 who were treated surgically for breast cancer at our facility. We excluded patients that underwent neoadjuvant chemotherapy. We then used a retrospective chart review to identify the imaging each patient received and collected the measurements that were recorded of the tumors by the radiologist for available mammography, ultrasound and MRI; pathology report measurements of the final specimens were used to compare. We subdivided the results by pathologic subtypes including invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC) and ductal carcinoma in situ (DCIS).
Results: 658 total patients met criteria for analysis. 323 had available mammography, 393 had available US and 231 had available MRI. Mammography overestimated tumor size by 0.67 mm (p = 0.463) while US underestimated tumor size by 1.45 mm (p < 0.05) and MRI overestimated tumor size by 3.06 mm (p < 0.05). When broken down, mammography overestimated specimens with DCIS by 1.93 mm (p=0.15), US underestimated by 0.56 (0.55) and MRI overestimated by 5.77 mm (p < 0.01). Mammography overestimated specimens of IDC mammography by 0.38 mm (p=0.77) while US underestimated by 1.22 mm (p=0.18) and MRI overestimated by 2.22 mm (0.16). With specimens of ILC all 3 imaging modalities underestimated tumor size.
Conclusion: Mammography and MRI consistently overestimated tumor size with the exception of ILC while US underestimated tumor size on all pathologic subtypes. MRI significantly overestimated tumor size in DCIS by 5.77 mm. All three imaging modalities were accurate in measurement of IDC tumors with no statistically significant difference in tumor size and pathology. All 3 imaging modalities underestimated tumor size in ILC, although only US significantly underestimated by 7.64 mm. It is important to understand the limitations of breast imaging when making surgical decisions. Mammography was the most accurate imaging modality for all pathologic subtypes and never had a statistically significant difference from actual tumor size.
