Thanks for the kind responses! I guess I never did post about Frankie's issues.

A few months ago she developed a knot on her back left knee and I assumed it was from wrestling with Riley. Unfortunately the knot grew rapidly into a mass so I took her to the vet to have it removed and biopsied. The initial word after having it removed was that it was a fatty tumor and the entire mass was removed.

Unfortunately the biopsy wasn't so good. The removed mass was a peripheral nerve sheath tumor. We've been in and out a few times now and the vets are not sure that enough tissue was removed and this kind of cancer has an extremely high re-occurrence rate. Luckily it is relatively low grade so that chance of it metastasizing is relatively low.

Right now I opted to not perform another surgery because there is still the chance that it was all removed the first time. Technically if it returns it should be in the same general location, so I've been checking her daily and if it does come back then we'll go in for the surgery with wider and deeper margins. If it comes back and they're not able to remove enough tissue due to her tight skin on the knee then we'll consider other options. Hopefully it will simply not return and we'll go about our happy hiking ways .