19 year old cat gone really down hill

My cat is 19. Up until now she has been very mobile and has no real problems.
She was always a big girl- 5.8kg last August. She had to lose some weight to have some teeth out in Feb. She got to 5kg. She then starring rapidly losing weight and is now 4kg.
Over the last 2 weeks she has been on steroids. The vet think she has cancer.
All the blood tests have come back fine.
She has had 6 seizures since Jan last year. 3 last year and 3 this year.no side effects from these and recovers within a few mins.
Over the past week she has lost most of her hair underneath her and has lost loads of strength therefore is struggling to walk.
She is hardly eating (when first on steroids she ate and drank loads)
She is drinking a bit.
Today she has had 2 wees and some cat milk and some water. Yesterday she had a few chunks of food and water.
She's not grooming and hasn't for 2 weeks.
The vet seems to have written her off.
I'm wondering to get a second opinion? She's on nothing apart from the steroids and today I haven't given her them because I want to give her a few days off them.
Amy advice or help?

It must be so hard to see your older cat's health change so much in what is quite a short space of time.  

Has your vet done tests other than standard blood ones, or is there some other reason they suspect cancer?   Did they talk you through what they were giving the steroids for and what they hoped you would see once they had been given?

19 is a 'good' age for any cat to achieve, but that is not to say they can not see a good few more if they are comfortable and happy in their life and are with people who care for them.  If you have got the impression that your vet is making assumptions based on age alone you may well be sensible in seeking a second opinion, but the first thing I would do is talk with your current vet about the details of what they believe is going on and how they have come to that conclusion.   If you then want to look at more options to help strengthen your cat and see her healthier and eating and drinking better ask them whether they think this is possible.   If not, why not. Then if you still feel uncomfortable about the vet care your cat is receiving you are well placed to talk with another vet and see how they would approach the situation.

Very often decisions are difficult, unclear, and come down to the quality of life your cat has.  If you still feel, once you have talked again with your vet and possibly also sought a second opinion, that the vet's view is not to do more, you might find the following article helpful in terms of whether you feel the need to put more pressure on vets for more intervention.
[article="29662"]When Is It Time Making The Difficult Decision  [/article]
Before I brought Mouse in to my home I had 2 older cats, one reaching almost 18 years and the other almost 22.  No matter how many years you have with them it never seems to be enough, and as the time passes by all that happens is they wrap them self more and more around your heart.   I wish you well in finding out what is happening for your cat, and reaching a comfortable understanding and agreement with your vet.

Thank you so much for reply.
Initially vet wondered about tyroid because of the weight lose. That blood test came back ok as did liver and kidneys.
She then thought brain tumour due to the seizures. Then when I saw her Tuesday she thinks lymphatic cancer due to the hair lose and slightly scabby skin. No other tests have been done. She could have mri but I don't want to put her through that.
She gave me steroids to try to put weight on her. This did increase her appetite for a week but now she hardly eats at all - only cat milk and water today.
I wonder whether another vet will help. It would have to be a home visit as I'm not taking her as she hates it.
I sleep next to her now and kiss her goodnight every night just in case.
I'm so upset.
I don't want to stop fighting for her and I feel no one is helping my baby girl

Was the fur loss before or after the vet gave her steroids?   I think steroids can cause some cats to loose fur.  

Have you tried her with different foods / textures to try and keep her eating. Because of her age, if she does not take in enough calories your cat can very rapidly become sick with fatty liver disease and this in itself make her feel sick and not want to eat.   What ever it is you can get her to take in it is worth trying, even if it is tuna or baby food rather than cat food - as long as there is no garlic in it.

She had some hair lose before the steroids but for a week it's completely gone from her stomach and paws.
Have tried all kinds of foods on her. Haven't tried baby food so will try that.

Just tried her on baby food and she wasn't interested. She's now hardly drinking water either.
I got her off the couch to try and get her to use her legs and she acted like she was frightened and weed.
I'm heartbroken

We lost her tonight. I'm heartbroken

     I am so sorry for your loss @sampoppy.   When fur family reaches the wonderful age of 19 with you it shows how precious and loved they are, and the hole you feel in your home is massive.  Keeping her as comfortable and calm as you could and not distressing her with lots of veterinary visits and tests can be desperately hard to do but is often the kindest and loving thing and I honestly believe you did everything she would have wanted and was best for her.  

You may not be able to see her or feel her fur but she is for ever going to be wrapped around your heart, and over time I hope you will be able to find comfort in thinking of her and remembering your time together. 

I'm very sorry for your loss. Telling you she lived to a good age doesn't help but she did.
You have my deepest sympathy.