Thanks again to all for your input. 

Due to my own experience, that is knowing that reading slides is somewhat subjective, 
I suggested the sample go to another pathologist and the 2nd outcome says that its not necessarily sarcoma but infection and some necrosis in the wrist joint of the front left leg.

Whatever it is,  sarcoma/cancer or infection, it has caused damage to the joint again prompting the vet to suggest that amputation would be a strong possiblitiy.

I am not hopeful this bun will do well missing a front leg, but i did hear of one that is doing fine. 

The saga continues. Again thanks for all your concern.