Hypoechoic nodule at 12 o’clock in the right breast may be caused by breast hyperplasia, breast fibroadenoma, breast malignant tumor and so on. 1. Mammary hyperplasia: a benign breast disease caused by abnormal development and degeneration of the mammary gland. The main symptoms are breast pain, lumps or nodules. 2. Breast Fibroadenoma: Breast fibroblasts are abnormally sensitive to estrogen and overgrowth occurs leading to the formation of fibroadenoma. Fibroadenoma can be manifested as easily palpable subcutaneous nodules. 3. Breast malignant tumor: Breast lump is a common symptom in the early stage of breast cancer. When the cancer cells infiltrate into the skin and grow, scattered hard skin nodules can be formed around the main lesion, which may also be accompanied by breast skin dimpling and orange peel-like changes. Nodules in the breast may also be caused by breast inflammation, trauma, etc. Corresponding examination should be conducted to clarify the condition and actively cooperate with the treatment to avoid delaying the condition.