Utility of MRI in diagnosis of molecular subtypes of breast cancer

Background: Breast cancer is a collection of diseases defined by distinct pathological (e.g., ductal, lobular, mucinous) and molecular characteristics (e.g., ER and PR, HER2 amplification, and more recently transcriptome-based classifications such as luminal and basal cancers). Molecular subtyping is beneficial for the diagnosis and individualized treatment of breast cancer.MRI is a supplemental technique to mammography and ultrasonography for the evaluation of breast lesions and to predict molecular subtypes of breast cancer. Studies have highlighted the value of DCE-MRI in reflecting the anatomic and functional properties of tumors and facilitating treatment.  Objectives: The aim of this work was to assess the utility of MRI as an accurate method for detection of molecular subtypes of breast cancer. Patients and Methods: a retrospective clinical study of 2-years enrollment duration. The study was conducted at Radiology Department, Assuit University Hospitals on 50 lesions, patient age ranging from 23 to 66 years old with mean age was (46.9 ± SD) years. MR imaging studies were performed using a 1.5 T Magnetom Vision scanner with dedicated bilateral phased-array breast coil (Siemens, Erlangen, Germany). MRI sequences were 1. Axial T1WI. 2. Axial T2WI. 3. Axial STIR. 4. Axial DWI and ADC. 5. DCE-MRI. Results: The study included 50 lesions; 21 lesions were Luminal A, 15 lesions were Luminal B, 10 lesions were HER2+, and 4 lesions were TN. Histopathology 39 lesions were IDC-NOS, 1 lesion was IDC (medullary type), 7 lesions were mixed pathology IDC + DCIS, and 3 lesions were ILC. As regard the correlation between the histopathological type and grade, both were specific in differentiation between the molecular subtypes. According to the MRI findings it was found that T2 Intratumoral signal intensity, STIR, and the margin of the lesion were highly specific in differentiation, both L.N status and number were found that they were highly specific in differentiation (p <0.001), while size of the lesion, T1WI signal, ADC values were found that they were non-specific in differentiation between the molecular subtypes of breast cancer. Conclusion: Breast MRI may help in assessing different molecular subtypes of breast cancer.