Most types of thyroid cancer are very treatable indeed, but some can be bad.
The worst is anaplastic thryoid cancer which has a median survival time from diagnosis of four to five months; it's one of the most aggressive cancers people can get.
It's rare, but unfortunately, it tends to be more common in older people.
Best wishes for him.
Yeah, I agree with you on anaplastic thyroid cancer. I'm trained in otolaryngology-head and neck surgery. Usually you do a trach on anaplastic because it is invasive of the airway. The other thyroid cancers usually compress the airway extrinsically, after they get really big.
If it's anaplastic, he's a goner.