There are many factors affecting axillary pain. Axillary pain may not necessarily be caused by breast enlargement, but breast enlargement can cause axillary pain, and the underlying cause of its development is painful discomfort due to impaired lymphatic return to the axilla caused by breast enlargement, which then causes reactive enlargement of the axillary lymph nodes. It is caused by reactive inflammation of the axillary lymph nodes.
Apart from mastopathy, other causes such as lymphatic reticulocytoma, acute mastitis and boils can also cause axillary pain.