Vuvlar tumor in a cat.

Hello,

2 weeks ago i had my russian blue sterilised cat (elderly not sure how old as she came to me as a stray but she was at least 15) put to sleep, 8 weeks before she was diagnosed with a vulval tumour and had it surgically removed, and came home from the op perfectly well. 3 weeks later her appetite dropped right off (several times she would approach her food but walk away again) and she became very lethargic, for last 4 weeks of her life she spent most of her time lying in the same spot in my spare bedroom or in my wardrobe, i put her on my bed at night. she had an ultrasound done and she had enlarged lymph nodes in her stomach and fluid in her stomach,the specialist did an aspiration from the back of the abdomen and
she had secondary cancer . the vet gave her injection of convenial but did not encourage her appetite so so exactly 8 weeks after being diagnosed with the tumour i had her put to sleep as i didn't want her to suffer any more. i can't find out very much about feline vulval tumours i would like to know are they always fatal and is it true it is very rare?

Thank You
Lisa