Breast enlargement does not usually cause enlarged lymph nodes under the armpits. Large lymph nodes under the armpit can be a result of a breast infection and possibly breast cancer. Breast enlargement is usually referred to as hyperplasia of the breast. Breast hyperplasia is usually palpable nodules, breast nodules are hard and pushable, it may be associated with menstrual cycle, and it is usually not accompanied by enlarged lymph nodes under the armpit. If the underarm to lymph nodes are enlarged, then it may be a bacterial infection, such as acute mastitis, which is common in primiparous women, mainly due to incorrect breastfeeding during breastfeeding. If bacteria multiply in the milk and cause an immune response, it may cause the lymph nodes under the armpit to swell. Besides, breast cancer may also cause enlarged lymph nodes under the armpits when the cancer cells metastasize to the armpits. If the lymph nodes under the armpit are enlarged, you should pay attention to it, and if there are manifestations such as bloody nipple overflow and cellulite sign, then you should consult a doctor as soon as possible so as not to delay your condition.