From my own personal experience:
I've always been gyno prone, and have had small lumps/swellings for years, even whilst off gear for years.
Back on earlier this year with Test/tren/deca/winny, got gyno bad pretty quickly, knew it was down to deca/tren, so bought some femara, and took 1/4 table for a week, and nearly all the swelling had gone, remarkable stuff. Therefore, i know it was prog induced Gyno, and for next cycle, i'll run a VERY low dose of Arimidex every couple of days with the deca or tren, if it flares up, i'll do the femara to cut it dead in it's tracks.