80% of breast lumps are benign. A cyst, by definition, is fluid filled. I think (not sure officially) that they are less likely to be cancerous if it is a cyst. Cancer tends to be solid, but not always.) Best thing is to have a biopsy to be sure. Either have a needle remove some fluid or just have it out.
I have not tried this, but I hear that reducing or eliminating caffeine can have a big impact on breast pain, as well as herbal supplements of evening primrose. Please ask a doctor before doing anything though.
Hang in there, odds are well in your favor!