1 year question after breast reduction; marble sized knot at the Center of the T closure?

1 year post op after breast reduction I have a marble sized knot at the Center of the T closure. I had it ultrasound which they wanted to do a biopsy. The needle aspiration came back fluid filled sisk with fatty narcosis. Grown this yr from 1.4 cm to 2.3 cm, now I will do core biopsy next wk. is it normal after having breast reduction surgery to start having lumps that grow? What is happening to cause this