Regarding Isolated tumour cells. I had the same thing, and couldn't figure out why I was still classified as having only 2 nodes affected, when I had these others floating around. Didn't these count? Anyway, I researched this, and I'm showing my findings below. Long and short is, that they do not count in the staging. They are tiny and can only be shown under a microscope, so I assume they will get wiped out with chemo. So don't worry too much about them!
6.4. Isolated Tumour Cells
Isolated tumour cells (ITC) are single tumour cells or small clusters of cells not more than 0.2 mm in greatest dimension that are usually detected by immunohistochemistry or molecular methods, but which may be verified with H and E stains. ITCs do not typically show evidence of metastatic activity (e.g., proliferation or stromal reaction) or penetration of vascular or lymphatic sinus walls. Cases with ITC in lymph nodes or at distant sites should be classified as N0 or M0, respectively.