Our doctor told us that if you're under age 45 at diagnosis, you can't be higher than Stage II. This is for differentiated papillary.
If you Google "thyroid cancer staging" an ACS site will come up first. It has a great page explaining the stages.
Excerpt:
Patients Younger than 45 Years
Stage I: Any T,
any N, M0: The tumor can be any size and may or may not
have spread to lymph nodes. It has not spread to distant sites.
Stage II: Any T,
any N, M1: The tumor can be any size and may or may not
have spread to lymph nodes. It has spread to distant sites.
Kelli