It turns out that Iago does have lung cancer. I cannot believe we're going through this again with another loved one. The vet has no idea how long he has or how he got lung cancer. She offered us a variety of treatments but it comes down to the fact that none of them will really get him "better" and probably won't enhance his quality of life. She said if it were her dog, she would just take it one week at a time.
He has a calcified tumor on his lung that has probably been there for a while. He also has three masses in his neck that are a result of the lung cancer. They are the ones we will have to worry about as they grow, two are on or near his larynx so they will eventually interfere with his breathing. I guess we'll be having some difficult decisions to make when it gets to that point. For now, we're just going to keep loving him like we've always done and hope we have some good time that we can all continue to spend together.
Here's one more picture of our cute guy. This was taken in the City House a few years ago on The Son's first Christmas. Iago thought this gift was for him. Silly doggie!