First, you will want to take Ava to your vet to get a proper
diagnosis.
Anything appearing to be growing on a cat is worrisome and I cannot
stand it until I get to the vet.

That said, what Ava has is probably something called Linear Granuloma,
not as bad as it sounds, not at all life threatening, but annoying to
the cat as the
little bumps apparently itch. It is part of a syndrome that is related
to allergic reactions. See this web site that someone here sent me to:

http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2002&PID=2544

I noticed bumps in a straight line on the back of my cat's legs,
running
along a tendon, or appearing to. The vet just felt her legs and told
me she had Eosinophilic Skin Disease--the rarest type appears in lines
and is sometimes referred to as "linear granuloma."

Cheeky also has asthma. My vet has elected to treat both her
ESD and asthma with shots of a steroid called Depo Medrol--but there
are other treatments and you should be aware of the fact that these
steroids have side effects such as the development of diabetes in cats
so disposed and other problems. You will want your vet to explain all
the options and all the side effects. Cheeks gets away with 3-4 shots
a year, and it keeps the bumps and the asthma away. It is my
understanding that nobody has proven that this condition (ESD) is in
any way life threatening or something that can shorten your cat's
life. But you need to have her seen.

Good luck and let us know what the vet says.