Skin sample's travel

I received a copy of the laboratory report from my vet clinic today.

There is a detailed description of the sample with the precise terminology doctors always use. 
Margins: Incomplete excision. Diagnosis: Skin and subcutaneous tissue: Fibrosarcoma. Behaviour: Malignant. Prognosis: Guarded.

She is not in pain, but due to the collar, very uncomfortable so much so that she does not eat unless I free her from the collar. I did so, and she ate some, but I had to put it back to prevent her from scratching. However, I was told that in a day or two I should be able to take the collar away for good. 

I feel guilty for having selfishly prolonged her life.