Very nice post with very correct detailing however there are different ways of staging and it doesn't necessarily have to be bigger in size before it can be classified as stage 2.

The method of staging you have used is called TNM staging. In TNM staging, when you have a lymph node involved, irrespective of the size it qualifies for stage 3

Also, I feel the factors that lead to cancer cannot be generalized ... As there are some carcinomas that affect children more than adults and also some sex than the other.
What do you think ?

I have never seen carcinoma been discussed this way tho as regards classifying invasive ductal carcinoma and also squamous cell carcinoma..

This was a really educative post and I think your classification is another stand of things.