The purpose of this study is to determine the relationship of the SWE elastic modulus and the molecular types of breast cancer .

Breast cancer is the most common cancer of women world wide, and it is the second leading cause of death following lung cancer. Treatment options for breast cancer have changed in recent years; primary conventional surgery is no longer considered the most appropriate option for every patient.

The Age, molecular subtype, spread of the tumor, axillary lymph node status(as it is the first site to be metastasized by breast cancer through the lymphatic vessels) , and patient preference are the main determinants of breast cancer treatment, and a multidisciplinary approach is necessary.

With the development of molecular biology, it has been recognized that breast cancer has large biological diversity and high heterogeneity, which result in different morphological subtypes. According to immunehistochemical indexes such as estrogen receptor (ER), progesterone receptor (PR),proliferating cell nuclear antigen (Ki-67), and human epidermal growth factor receptor-2 (HER-2), clinicians determine 4 main molecular subtypes of breast cancer : -luminal A (ER+ or PR+, HER2-, andKi67 < 15%).

• luminal B (ER+ or PR+, HER2-/+,and Ki67 > 15%).
• triple negative (ER-, PR-, andHER2-).
• HER2+ (ER-, PR-, and HER2+). Determination of the molecular subtype of is the most important factor in systemic breast cancer treatment ; for example, it is generally preferred to use endocrine therapy in cases of hormone receptor positivity, anti-HER2 drugs in cases of human epidermal growth factor receptor2 (HER2) positivity, and chemotherapy in triple-negative patients.

The molecular subtype also determines recurrence and prognosis. For example, the triple negative subtype shows recurrence more frequently than other subtypes, while the luminal A subtype has a better prognosis.

Ultrasound (US) is an important modality for the detection and characterization of breast masses; it is also the first guiding method to be chosen for percutaneous biopsies in daily practice. Elastography is us based imaging modality recently developed to measure the elasticity of tissues using sound waves. Two-dimensional shear-wave elastography (SWE) is a newly emerging elastography technique, which can display tissue stiffness in a quantified form to obtain the biological information of the primary lesion . At present, many studies have verified the diagnostic value of SWE for benign and malignant lesions in breasts . The technique has been widely employed to check the thyroid, pancreas, kidney, prostate, liver, and other organs while few studies about axillary node metastasis (ANM) and its application for the molecular classification of breast cancer were reported .

The purpose of this study is to determine the relationship of the SWE elastic modulus and the molecular types of breast cancer .

Inclusion Criteria:

• Women who were diagnosed with invasive breast cancer and did not receive neoadjuvant treatment and who previously did not have an operation on the same breast or axillary fossa .

Exclusion Criteria:

• Women who were diagnosed with non-invasive breast cancer and who receive neoadjuvant treatment and who previously had an operation on the same breast or axillary fossa .
• patients who expressed their oppositionto the use of their personal data.

Based on determining the main outcome variable ,the estimated minimum required sample size is 60 patients.

The sample size was calculated using Epi-info version 7 software, based on the following assumptions:

Main outcome variable is correlate various pattern of non mass lesions with histopathology for further management. Based on previos accuracy is 81%. Based on this percentage confidence limits of 6% and a confidence level=80%.