Help me to understand and make friends with my lymph nodes :)

Good questions--and here is what I know from being a patient.

Does it mean that there's a likelihood my breast cancer hasn't spread anywhere else?
No spread to lymph nodes is a good sign, but there is really no way of knowing with total certainty when/if breast cancer will spread.

Does it mean that it likely didn't spread TO my breast from somewhere else?
That would be unusual, and if so, it would not be breast cancer but a cancer from its place of origin. Did anyone imply that might be the case? I think your oncologist could give this a direct answer.

AIs are recommended for me and I plan to give them a try just to see.
My own experience with letrozole (an AI) has been good. I also didn't have chemo, due to kidney disease and other co-morbities. My diagnosis was 3 years ago, when I was 68, and I have no side effects from letrozole.

All best going forward. It can be hard to sort through decisions--I know from experience!

Good questions!
I’ll try answering your first one based on my experience and what my doctors told me. I’ve had breast cancer twice. The first was about 10 years ago when I was 42. Super low grade, hormone positive, left breast only. No BRCA or family history. Had a double mastectomy, clear margins and a sentinel node biopsy that was clear. No radiation or chemo was recommended, but I was prescribed Tamoxifen. I researched Tamoxifen and became concerned that other health concerns could develop from it—especially ones that ran in my family. At the time, I was told that I had a 6% chance of the BC returning. I rolled the dice and declined Tamoxifen.
Fast forward 8 years—the breast cancer returned. Same stuff, left axilla (arm pit area) slightly higher grade (as is typical, I’m told), all in the lymph nodes. Because the cancer came back in my lymph nodes, it was recommended that I under go chemo, then radiation and take an AI. I did all that and have continued with the AI.
When I asked my doctors about the mechanism of reoccurrence (Why did the BC return when I had no breasts and when my sentinel node was clear?), I was told that it was impossible to know precisely what happened. But one doctor told me what was possible. She said that one cell from BC #1 could have traveled past the sentinel node and lay dormant for years. BC #2 happened when the cell decided to wake up and start multiplying. It just takes one cell.
I think it is logical to conclude that if you have clear sentinel nodes that you are less likely for reoccurrence. But it’s not a guarantee. As another doctor told me, cancer doesn’t follow logic. We can observe patterns of its behavior and that can help determine treatment.
Wishing you the best of health as you complete your radiation treatments!

Wow after reading post from monimoa thought at first was reading my history however older than you I think. But so similar - my hormone positive breast cancer showed up in my lymph nodes under my left arm area 20+ years later, even with aggressive treatment with double mastectomy, clear nodes and tamoxifen for 5 years returned as stage 3. My current surgeon said it is nearly impossible to get ever cancer cell - but the surprise was the recurrence in the lymph nodes after so many years. Currently on a hormone inhibitor and after 6 month there was significant reduction of cancer activity showing on the MRI. I then had surgery where they removed 27 nodes and 11 nodes still showed with cancer cells. After surgery also had 16 rounds of radiation for mop up. Now my oncologists want me to take CDK 4/6 for 2 or 3 years - I did try Verzenio for 1 month - made me very sick with negative blood tests. I stopped the drug. I have major questions about "cancer" treatments and why oncology is so determined to weaken/destroyed my immunity when it is already struggling with a cancer return/my immunity had kept the cancer in remission for years - guess with age our immune system declines but seems a better treatment would involve strengthening my immune system instead of destroying it. I feel if I allow oncology to further destroy my own immune system - once treatments finish my cancer will return with a vengeance and have no ability to fight it. I visit my oncologist next week and have questions about getting my immune system up to speed - hope they might offer me Anktiva now a FDA-approved immunotherapy designed to activate the body's natural immune system to target and attack cancer cells. Would love to hear if others are looking in to similar therapy/treatments.

I've never heard of Anktiva but I'll be asking my oncologist about it! Thank you for sharing and good luck to you.