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 contrast-enhanced 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+ (n = 119) and HER2+ (n = 94), larger size, round/oval mass shape, smooth mass margin, and rim enhancement on DCE-MRI were significantly associated with TNBC (n = 58; 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 (P = 0.099). Tumour size (P = 0.009), mass margin (smooth, P < 0.0001; irregular, P = 0.020), and ADC values (P = 0.002) on DCE-MRI 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.