These pink bumps are kind of a "What should I do?" situation. If there's little change in it and kitty seems well...you can take the risk it will stay benign.
But these lumps are signs of several forms of tumour/cancer, as well as hypertrophic cardiomyopathy.
Here, I'll put a link that describes symptoms of the above...(if it will work, sometimes they won't show). But if kitty is acting sick, you will have to get him checked and possibly treated.
www.acay.com.au/~j-kivits/feline.html
(this is a layman's description of disease progression. You didn't go into detail, thought it may save you time of describing other symptoms)
we... my cat not welll....some red color bubble is on its tummy...what [url=http://www.paintyourlife.com/galleries/cat-portraits.asp][b]cat portraits[/b][/url] should i do know....please help me too in this matter..i am too worried
Hate to say this but don't waste your money unless it grows unusually large or changes color or shape. My himalayan has the same growth and when it was smaller I asked my vet and she reassured me that it was probably nothing and to just watch it. It has grown a little in the past few years and she keeps telling me not to worry about it. It is shiny pink and the size of a BB pellet. It is also around her neck.
You should have him checked and have the lump biopsied if necessary. It could be a cancerous growth and it would be good to know if it's malignant or can turn malignant.