Comparison of Breast Tumor Size Measurement Using Ultrasound and Mammography with Pathologic Report Following Mastectomy or Lumpectomy

One of the most important factors in determining prognosis and therapeutic plan in patients with breast cancer is tumor size. Our aim in this study was to compare the estimated tumor size in two common imaging modalities, ultrasound and mammography with pathologic assessment.

In this cross sectional study, we analyzed 287 patients with breast cancer diagnosis whose pathologic specimen was reported in pathology department of Omid hospital (Isfahan, Iran) from March 2015 to March 2020. The difference in tumor size were evaluated based on imaging and pathological reports. Then, we classified them in three groups as concordant, underestimated, and overestimated for which the effect of various factors such as age, tumor type, T stage and molecular subtype on accuracy of each modality was assessed.

Concordance rate was 58.3% in ultrasonography and 51.7% in mammography. Ultrasonography and mammography respectively underestimated the tumor size in 30.6% and 31%, and overestimated in 11.1% and 17.2% of cases indicating no statistically significant difference between the two modalities. Ultrasonography and mammography underestimate large tumors more commonly than small tumors. For tumors smaller than 20 mm and HER2- tumors, ultrasonography is more accurate than mammography. Also, mammography estimates the size of Luminal A tumors compared to ultrasound.

There was no significant difference between the accuracy of ultrasonography and mammography measurement of tumor size, but inherent factors such as T stage, her2 expression and molecular subtype influence this issue.