Different causes of swollen lymph nodes
You can have swollen lymph nodes for several reasons, which include strep throat, an ear infection, or an immune system disease. Cancer can also cause swollen lymph nodes. Lymphoma [6] is a form of cancer that begins in the lymph nodes. You must know that cancer cells can also spread from other parts of the body to lymph nodes, especially the ones that are closest to the primary tumor.
In some cases, breast cancer may spread to the lymph nodes under the arm or near the collarbone. Once in the lymph system, cancer cells can move through the lymph vessels to distant parts of the body, where they can form new tumors (metastasis).