On Easter night my wife and I were dropping off our Bullmastiff, Luna, at her Grandma's house for a trip out to see my father who is not doing too well at 85. Before we left Luna started coughing up blood and we rushed her to the emergency vet. Turns out she had advanced lung cancer, the x-ray was completely white. We took her to our vet on Monday and made the decision to put her down. She was happy and appeared to be pain free at the time. Our vet told us that at 10 years old she was the equivalent of 90 for her breed and that chemotherapy would not be a good option. It would make her suffer and had very low probability to help with the cancer that advanced. This was our second dog and second Bullmastiff and was just as tough as the first time. Truly the only bad thing about having a dog is that this moment will inevitably arrive.
Here is her last pic, that morning at the vet, she was as happy as always to go and see all her friends there.