I Had A Breast Biopsy Of A Cyst...it Started As

I had a breast biopsy of a cyst...it started as a simple cyst, at least that is what I was told. A year later, it grew 4mm and appeared to be solid. During the biopsy, the radiologist noticed that it still appeared to be hollow with "debris". He was hopeful that it was just a complex cyst. Turns out, it is invasive mammary carcinoma.
1. Is this carcinoma the same as IDC? 2. Can it really be this without being a solid tumor?