Very small 1cm swollen lymph nodes under arms. been there for a year or so. very soft and moveable. no infection. why is this?

Fatty tumor: Likely it is a lipoma which is a benign fatty tumor. If it bothers you or if it grows or changes characteristic then have it removed.

Could be normal: Several lymph nodes are present in your axilla. In thin patients these lymph nodes can be easily felt. The presence of a lymph node is not an abnormality. Should it change in size, become firm and immobile, or if you have other worries about it, see your friendly doctor.