Triple-negative invasive breast cancer on dynamic contrast-enhanced and diffusion-weighted MR imaging: Comparison with other breast cancer subtypes

Objectives To determine the MRI features of triple-negative invasive breast cancer (TNBC) on dynamic contrastenhanced MR imaging (DCE-MRI) and diffusion-weighted MR imaging (DWI) in comparison with ER-positive/HER2- negative (ER+) and HER2-positive cancer (HER2+). Methods A total of 271 invasive cancers in 269 patients undergoing preoperative MRI and surgery were included. Two radiologists retrospectively assessed morphological and kinetic characteristics on DCE-MRI and tumour detectability on DWI. Apparent diffusion coefficient (ADC) values of lesions were measured. Clinical and MRI features of the three subtypes were compared. Results Compared with ER+ (n0119) and HER2+ (n094), larger size, round/oval mass shape, smooth mass margin, and rim enhancement on DCE-MRI were significantly associated with TNBC (n058; P<0.0001). On DWI, mean ADC value (×10 ^-3 mm ²/s) of TNBC (1.03) was higher than the mean ADC values for ER+ and HER2+ (0.89 and 0.84; P<0.0001). There was no difference in tumour detectability (P00.099). Tumour size (P00.009), mass margin (smooth, P<0.0001; irregular, P00.020), and ADC values (P00.002) on DCEMRI and DWI were independent features of TNBC. Conclusions In addition to the morphological features, higher ADC values on DWI were independently associated with TNBC and could be useful in differentiating TNBC from ER+ and HER2+. Key Points ̇ Triple-negative breast cancers (TNBC) lack oestrogen/progesterone receptors and HER2 expression/amplification. ̇ TNBCs are larger, better defined and more necrotic than conventional cancers. ̇ On MRI, necrosis yields high T2-weighted signal intensity and ADCs. ̇ High ADC values can be useful in diagnosing TNBC.