Thanks for your quick reply.
A biopsy is the only way to tell for sure if the bone growth is osteosarcoma, or some other type of tumor, or a fungal infection. Certainly, osteosarcoma is the most common type of bone growth in dogs, especially large breed dogs like yours.
If it truly is osteosarcoma, you will get the longest average survival time with amputation and chemotherapy. Amputation will get rid of the pain, and dogs do very well after amputation. Average survival time after diagnosis is 4-5 months, whether or not amputation is done. So, you can just give pain medication that your veterinarian may prescribe, but it won't completely get rid of the pain like an amputation would do. If you have amputation and chemotherapy performed, the average survival time increased quite a bit - from close to 1 year, to potentially over 3 years in some cases. Side effects of chemotherapy in dogs is not nearly as severe as it is in people, so dogs tolerate it better. It's good that your veterinarian did not see any sign of cancer in the lungs at this time, but we know that when osteosarcoma is diagnosed, it generally has already spread, even if it can't be seen on X-rays yet.
So, overall, I would highly recommend at least amputation of the affected leg, to try and make Tequila as comfortable as possible. And if you are able to do it, chemotherapy really has the potential to extend her life quite bit.
I really encourage you to read a great article on osteosarcoma in dogs here.
I hope this helps. Let me know if I can assist further.
Dr. Dave