Hi Cat and welcome. Its a bummer you had to go in for a second surgery but at least that should get to the very bottom of the cancer and you can feel less frightened about the possibility it might come back.
I had the mastectomy left side straight up but the lymph node came back positive so I had the axillary clearance to make sure it hadn't gone into any more nodes. Luckily it hadn't gone to any more nodes and I was left wondering why the surgeon didn't take say 5 or 6 nodes at the initial surgery and save me a second surgery. I am still a bit cranky about that but never mind, what's done is done.
They would already know what type of cancer it was and if it is ER etc positive or not and that will play a part in what further treatments you will have and what chemo type will maximise the success in mopping up any stray cells floating about. Radiation therapy may be required and probably hormone therapy as well.
It was explained to me that all the specialists from a few hospitals get together online with the results and they plan a strategy for further treatment from there. Its a slow process and get used to lots of appointments in the future. You get good at amusing yourself in waiting rooms. Then one day Voila, no more appointments and for a while you will feel lost and not know what to do with yourself lol.