First of all, pain in the breast is rarely associated with cancer,if the lump has disappeared, it could simply mean a cyclical fluctuations in hormone levels, which could be effecting your breast tissue.Cysts tend to enlarge and shrink before and after menstruation.
Even though the lump has gone,it could still reappear before your next menstrual cycle.
Seeing a breast Surgeon is important because first of all, he/she will explain to you in details what the radiologist has stated on your tests report and also if further investigation is needed.
Since you have a family history of BC, I would advise you to keep the appointment as scheduled.It might be really nothing to worry about..but it's always better to make sure.
Best wishes and good luck..