What would cause reoccurring swollen lymph nodes under your armpits?

Lymphadenopathy: Studies show that approximately 1.1% of primary care patients presenting with lymphadenopathy have malignancy. The axillary lymph nodes drain the breast, chest wall and upper extremity. Lymphadenopathy that is persistent >3 weeks should be investigated. Most causes of axillary lymphadenopathy are reactive in nature. A full medical history and physical exam should be performed.