Breast cancer in adolescents is enormously rare. Lymphoma must always be considered with enlargement of the lymph nodes, although in the vast majority of such cases, lymph nodes that are enlarged due to lymphoma are not significantly painful.
While this painful lump is not highly likely to be related to cancer, as I cannot examine you, it is best to have your doctor take a look, just to be on the safe side.
Sincerely,
Robert A. Wascher, MD, FACS
www.doctorwascher.com
Author, "A Cancer Prevention Guide for the Human Race"