Hi, There are several potential causes of pain in the underarm and breast area that radiates through the arm. Some possible causes include: * Muscle strain: Strain or injury to the muscles in the chest or arm can cause pain in the breast and underarm area that radiates down the arm. * Costochondritis: Costochondritis is an inflammation of the cartilage that connects the ribs to the breastbone. It can cause pain in the chest and underarm area that may radiate down the arm. * Breast conditions: Certain breast conditions, such as mastitis or breast abscess, can cause pain in the breast and underarm area. * Lymph node enlargement: Enlarged lymph nodes in the underarm area can cause pain that radiates to the arm. * Nerve compression: Nerve compression or damage in the chest or arm can cause pain that radiates down the arm. In addition to the pain, the symptoms of dizziness, lightheadedness, and nausea could be related to a separate medical issue. Some potential causes of these symptoms include: * Low blood pressure: Low blood pressure can cause dizziness, lightheadedness, and nausea. * Inner ear problems: Inner ear problems, such as labyrinthitis or Meniere s disease, can cause dizziness and nausea. * Anxiety: Anxiety can cause dizziness, lightheadedness, and nausea. It is recommended to seek medical attention from a healthcare provider to determine the underlying cause of your symptoms and receive appropriate treatment. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician