Diffusion-weighted imaging of breast invasive lobular carcinoma: comparison with invasive carcinoma of no special type using a histogram analysis

Background: To investigate the imaging findings and visibility of breast invasive lobular carcinoma (ILC) on diffusion-weighted imaging (DWI) and compare quantitative apparent diffusion coefficient (ADC) metrics of ILC and invasive carcinoma of no special type (NST) using a histogram analysis. Methods: We performed an observational retrospective study of 629 consecutive women with pathologically proven ILC and invasive ductal carcinoma of NST, who underwent 3-T MRI including DWI, between January 2017 and August 2020. Results: After propensity score matching, 71 women were allocated to each group. On DWI, 9 (12.7%) lesions of ILC and 4 (5.6%) invasive carcinomas of the NST were not visualized. For the tumor visibility on DWI, tumor size, tumor ADC value, and background diffusion grade were significantly associated with the visibility score in both groups (all P<0.05), whereas the mean background ADC value was not significant (P>0.05). The mean ADC (1.226x10(-3) vs. 1.051x10(-3) mm(2)/s, P<0.001), median ADC (1.222x10(-3) vs. 1.051x10(-3) mm(2)/s, P=0.002), maximum ADC (1.758x10(-3) vs. 1.504x10(-3) mm(2)/s, P<0.001), minimum ADC (0.717x10(-3) vs. 0.649x10(-3) mm(2)/s, P=0.003), 90th percentile ADC (1.506x10(-3) vs. 1.292x10(-3) mm(2)/s, P<0.001) and 10th percentile ADC (0.956x10(-3) vs. 0.818x10(-3) mm(2)/s, P=0.008) were higher in ILC than in invasive carcinoma of NST. Additionally, the ADC difference value of the TLC was higher than that of invasive carcinoma of NST (1.04x10(-3) vs. 0.855x10(-3) mm(2)/s, P=0.027). Conclusions: On DWI, the visibility of ILC was lower compared to invasive carcinoma of NST. ILC showed higher quantitative ADC values and higher ADC difference values.