Lobular is sneaky and difficult to assess--tumours are often larger, or more numerous, than first thought.
Scan and tests are stressful and nothing is without some element of risk--no-body likes being in a machine with chemicals swishing through their veins--but it sounds like you are being offered a thorough assessment. Which is pretty sensible given the form of the disease you have won in life's crappiest lottery.
Don't worry too much about the grading business; the main game is your medical team figuring out exactly what is going on and what can be done about it. This stuff is confusing and confronting and it takes a while to get used to a whole new language. It also requires a level of trust which doesn't come naturally to some people. Hang in there. Mxx