The numbness of the right hand after 4 years of breast cancer surgery may be caused by poor blood circulation, cerebrovascular blockage, cervical spine disease, tumor recurrence and metastasis. 1. Poor blood circulation: if the patient’s hand or arm is in the state of pressure for a long time, the blood may not circulate well, which will lead to the symptoms of weak and numb hand in the long run. 2. Cerebrovascular blockage: if the cerebrovascular blockage, the blood in the brain may not be able to be supplied to the limbs in time, and the symptom of weak and numb hands may occur for a long time, so the patient’s weak and numb right hand after breast cancer surgery may be caused by cerebrovascular blockage. 3. Cervical spine disease: if the patient suffers from cervical spine disease, the ligamentum flavum and posterior ligamentum behind the cervical vertebrae may compress the spinal cord, and the patient will have the symptom of weakness of limbs, so the lack of strength and numbness of the right hand of the patient after breast cancer surgery may be caused by cervical spine disease. 4. Tumor recurrence and metastasis: it is also possible that the recurrence of breast cancer and metastasis may compress the tissues and lead to the obstacle of venous return, which may cause the numbness of the right hand. It is recommended that patients should go to the hospital in time when their right hand becomes numb after 4 years of breast cancer surgery, and then follow the doctor’s instruction to receive treatment after finding out the reason.