Abstract: Objective To explore the relationship of diffusion weighted imaging (DWI) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) quantitative parameters with molecular subtypes of breast cancer, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2), and Ki-67 expression. 
Methods In total, 116 patients with breast cancer were selected, and all patients received DWI DCE-MRI examination. Different molecular subtypes of breast cancer were analyzed, and differences in ER, PR, HER-2, Ki-67 expression tissue apparent diffusion coefficient (ADC) values, volumetric transfer constants (Ktrans), and reverse rate constants (Kep) were analyzed. 
Results The ADC value of patients with clinical stage Ⅲ-Ⅳ was (0.92±0.23) × 10-3 mm2/s, which was significantly lower than that of patients with stage Ⅰ-Ⅱ breast cancer (P＜0.05), while Ktrans was (1.47±0.22) min-1, which was significantly higher than that of patients with stage Ⅰ-Ⅱ breast cancer (P＜0.05). The ADC value of patients with triple negative type was (0.87±0.19) × 10-3 mm2/s, which was significantly lower than that of Luminal A type, Luminal B type and Her-2 type (P＜0.05). The Ktrans of the triple negative type was (1.94±0.28) min-1, which was significantly higher than that of the Luminal A type, Luminal B type and Her-2 type (P＜0.05). The Kep of triple negative type was (1.76±0.21) min-1, which was significantly higher than Luminal A type and Luminal B type (P＜0.05). The ADC value of ER negative expression tissue was (0.96±0.21) ×10-3 mm2/s, which was significantly lower than that of ER positive expression tissue (P＜0.05). The ADC value of Ki-67 high expression tissue was (0.99±0.19) × 10-3 mm2/s, which was significantly lower than that of Ki-67 low expression tissue (P＜0.05). The Ktrans and Kep values of ER negative expression tissues were (1.41±0.26) min-1 and (1.63±0.26) min-1, respectively, which were significantly higher than those of ER positive expression tissues (P＜0.05). The Ktrans and Kep values of PR negative expression tissues were (1.53±0.27) min-1 and (1.68±0.25) min-1, respectively, which were significantly higher than those of PR positive expression tissues (P＜0.05). The Ktrans of Ki-67 high expression tissue was (1.30±0.22) min-1, which was significantly higher than that of Ki-67 low expression tissue (P＜0.05). There was no significant difference in ADC values and DEC-MRI quantitative parameters among different HER-2 expression tissues (P＞0.05). 
Conclusion DWI and DCE-MRI quantitative parameters are correlated with molecular subtypes, ER, PR and Ki-67 expression of breast cancer, but are not significantly correlated with Her-2 expression, which is worthy of further study. 

Key words: breast neoplasms, magnetic resonance imaging, diagnosis