Confused

So I have been lurking around these boards for a while now. You ladies are warriors.

A couple months ago I found 2 new lumps on my left breast. Went to doctor, diagnostic mammogram and ultrasound done. During my conversation with the radiologist he mentioned an area in my left breast that has been growing over the past 4 years now but just kinda dismissed it. The ultrasound found 2 cysts which is what I felt. Due to pain they were aspirated on the 31st by the same radiologist.

Back history...I'm 54, had a complete hysterectomy, with ovaries, 16 years ago. Have been on the same estrogen only, same dosage, hormones for 16 years. In 2010 I had a breast reduction from a very large DD to a C cup.

The mammo before my surgery in 2010 showed an area of density in each breast. In 2015 my mammo showed no density in right breast and a small area of density in my left. Which I had no idea about any of this.

After my aspiration I asked the radiologist again about what he saw and the fact that its growing. Radiologist showed me my mammo from 2010, 2015, 2016, 2017 and 2018. On the last 4 mammos the "parachymal density" has grown quite a bit. Very visible and obvious. He agreed with me that these areas were removed with my surgery. ONLY after I asked him about it he thought I should have another mammo in 3 months to see if it is still growing. (His report on my mammo has now changed to birads 3 with parachymal density that is growing)

I'm a bit confused as to his concern when I questioned him about it. I'm also confused as to why this area is growing. There has been no hormone changes, no weight gain or loss, no other factors for this density growth from what info I can find. I found info on parachymal density but not why its steady growing and what that means. Will this area be more likely to develop into cancer.

Anyone know anything about this?