Solid nodules in the left breast may be physiological, cystic hyperplasia of the breast, fibroadenoma of the breast, breast cancer and so on. 1. Physiological nodules, most commonly seen in pubertal development, estrogen level increases, appearing breast hard lump-like changes, is a normal physiological phenomenon, does not need special treatment. 2. Breast cystic hyperplasia, which occurs in women of childbearing age, is characterized by cyclic pain in the breasts and the formation of hyperplastic nodules. The degree of pain and the size of the nodules change with the menstrual cycle, i.e., the pain is aggravated during menstruation and relieved after menstruation. 3. Breast fibroma, which is more common in young people, manifests as a lump in the breast and can be painful. On physical examination, the surface of the lesion is smooth, with clear boundaries and good mobility. Ultrasonography will find a lump with intact periphery, if the lesion increases gradually, surgical excision can be chosen as the treatment method. 4. Breast cancer, with no obvious characteristic manifestation in early stage, in advanced stage, irregular shape, hard and poor mobility lumps can be touched in the breast, accompanied by orange peel sign or dimple sign, once diagnosed, radical surgery for breast cancer should be actively carried out. Solid nodule on the left side of the breast should also be considered for other reasons such as breast trauma, mastitis, etc. It is recommended that patients with solid nodules in the breast should go to the hospital in time and be treated accordingly under the professional guidance of the doctor.