Thank you all for your responses.  Today is surgery day.  We've been waiting for this day for almost a week.  Nilla was admitted to the ICU last Tuesday and for the past 6 days the vets have been preparing her for surgery.  The complication was that mast cell tumors release histamines and heparin.  The histamines caused the tumor to be the size of a naval orange as well as caused her entire leg from paw to hip to swell three times the normal size.  The surgeon said they could not perform surgery with the tissue so swollen.  The other issue was the tumor was releasing heparin, which is a blood thinner.  The site of the tumor had broken through the skin and she was dripping blood that would not clot.  She required a blood transfusion and medication to counter the effects of the heparin.  Without that, she would have bled out during surgery.  She has been on IV pain meds, IV fluids, and nasal feedings, as well as steroids for the past 6 days.  Hopefully after today's surgery she can begin the healing process.  We are staying cautiously optimistic about her recovery, but at almost 13, she had already lost a lot of muscle mass in her rear quarters and the surgeon told us that while most dogs do well on three legs, we need to be prepared that her remaining rear leg may not be as strong as it needs to be to help her get around easily.  I ended up purchasing the Ruffwear Webmaster harness with the brush guard -- I hope that provides enough support to her.  If not we will opt for more sling-like support.  And yes, Nilla has been dealing with anorexia for the past several months.  She contract giardia over the winter and ever since then has been a lab who doesn't love food.  She will sometimes go several days barely eating, while other times she will happily gobble up her meals.  We recently switched her from dry kibble to canned food, which helped somewhat, but even with the tasty wet food, she would often eat 3/4 of the food and walk away.  She dropped from 64 pounds in the winter to 58 pounds right before hospital admission.  Needless to say, we're going through a lot with her, but we are committed and determined to do whatever it takes to give her a quality life.  Her most favorite thing to do is to roll in the mud.  If she can get to a point where she can wallow and roll in mud again, this will all be worth it.  I feel so lucky to have a group like Tripawds to teach us, guide us, listen to us, and support us.