الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Breast cancer is a heterogeneous disease with many histological and molecular subtypes that have a different response to therapy and prognosis. Traditional criteria for treatment choices were the size of the tumor, histological grade, lymph node involvement, local invasion, and distant metastasis. However, patients with the same stage of cancer and similar histopathological characteristics may show different clinical behavior and prognosis. Advances in gene expression analysis with DNA microarray technology have provided new molecular subtypes; Luminal A, Luminal B, Human epidermal growth factor receptor 2 (HER2) enriched & triple-negative (basal-like), immunohistochemical (IHC) staining is a reliable surrogate for these subtypes [26], [127].
Luminal A subtype is associated with a low proliferation index (Ki-67), accounts about for 50-60% of all breast cancers, and has the best prognosis. Luminal B subtype is associated with a high expression of the Ki-67 proliferation index, accounting for 20 % of all breast cancer, and has a poor prognosis as compared to Luminal A. Luminal B characteristically do not over express HER2/ neu, but approximately 30% of them will be HER2 enriched, HER2+ subtypes account for 10% of all breast cancers and are characterized by the absence of hormone receptors and high expression of the HER2/neu gene. Triple-negative subtype accounts for 7-16% of all breast cancers and is characterized by the absence of expression of hormone receptors and HER2+, associated with a high expression of cytokeratin genes of high molecular weight. This subtype is associated with less differentiated invasive carcinoma and accounts for about 70% of breast cancers on BRCA-1 mutated females. HER2+ and Triple negative subtypes show a good response to chemotherapy but have the worst overall survival [142], [143].
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is an efficient imaging technique in evaluating breast cancer patients for preoperative surgical planning and treatment choices. The correlation of imaging findings with molecular subtypes of breast cancer is an emerging area of recent studies [122].
The aim of this study is to assess the utility of MRI as an accurate method for detection of molecular subtypes of breast cancer by reaching our standard parameters for detection of these molecular subtypes.
Our study included 71 female patients with 206 lesions, included patients who diagnosed as breast cancer and had complete medical records, that include: ultrasonography, soft tissue mammography, MRI, biopsy with histopathology and immunohistochemistry.
MRI breast study includes both conventional and functional methods with basic standard technique as T1WI, T2WI, STIR axial &sagittal sequences, functional MRI including DWI (specifically ADC values) and further DCE-MRI to characterize different patterns of enhancement either mass or non-mass enhancement following ACR BI-RADS-MRI lexicon classification, and including different specific kinetic curves of enhancement (TIC) and color coded maps.
Luminal A which were more common in our study presented as a mass lesion with an irregular or spiculated margin, lower ADC values and heterogeneous enhancement with type II or III TIC, MRI showed moderate agreement by Cohen’s Kappa test, however luminal B subtype shared common imaging findings with luminal A , its margin was irregular or spiculated with heterogeneous enhancement, but it was commonly presented as non-mass enhancement as HER2+ tumors, and also exhibited central breakdown with low ADC values in the solid areas and higher ADC values in the degenerated areas, this variability in the radiological findings of luminal B tumors could be due to the fact that they shared estrogen receptor positivity with the luminal A and they also share HER2-positivity with the HER2 subtype tumors.
HER2+ tumors were the most to be presented as non-mass enhancement, the presense of multifocality, multicentricity and bilaterality as well as axillary adenopathy could help in diagnosis and they showed type III TIC with fast kinetics.
MRI showed substantial agreement by Cohen’s Kappa test in both luminal B and HER2+ subtypes.
TN subtype showed some specific features as smooth margins, a high T2 signal intensity and rim enhancement post contrast, with higher ADC values and TIC is variable nearly equally between II and III with few cases showed type I TIC, TNBC was diagnosed by DCE-MRI nearly in all cases and had a perfect agreement by Cohen’s Kappa test, thus we can diagnose TN tumors by DCE-MRI better than mammography and ultrasonography which give overlapping criteria with benign lesions, and also we can easily differentiate TN tumors from other breast cancer molecular subtypes by DCE-MRI.
Conclusion
MRI helps in differentiating molecular subtypes of breast cancer with perfect agreement in its use in diagnosis of TN tumors by combining conventional and functional MRI features, substantial agreement for the use of MRI noted in both luminal B and HER2+ tumors while luminal A tumors had a moderate agreement, further studies are recommended to use MRI as an accurate method for diagnosing TN breast cancer.