It sounds like an abscess
formation, or cellulitis.
Cellulitis is an
d it's characterized by redness, swelling, warmth, an
d pain or tenderness.
You should see a dermatologist who will treat it by draining it an
d most probably followed by a course of an
Even though I don't believe that this has an
ything to do with breast can
cer,however I urge you to consult a doctor soon an
d get it treated to prevent further complications.