Contact the ANA and ask them for their informational brochures; they are free for the asking.
Also, encourage Bobby to join - or at last lurk on - the Forum.
Being diagnosed with an AN is shocking, but it's nice to know that there are others who have been there and it's also nice to interact with others who have had/have the same issues.
Sometimes the Forum can be a bit scary, so make sure you and Bobby take things with a grain of salt and keep in mind that everyone's experience is somewhat unique.
Based strictly on the size of Bobby's AN, he should have the options of watching & waiting, surgery, or radiation; but location is also a factor when it comes to treatment.
Whatever he chooses to do, I can't stress enough that it's a personal choice and he needs to make his own decision - after educating himself.
It's also vitally important to find a doctor who has lots of experience in treating ANs. There is a list of doctors/facilities on the ANA's main webpage that are considered Centers of Excellence. The ANA does not endorse them, but they have passed a rigorous set of "rules" to become Centers of Excellence. This isn't to say that a doctor/facility not on the list isn't qualified, but it's a great starting point.
Best,
Jan