As above... there is a very small - very small - almost miniscule - risk that a FNA can cause spread of a cancer. However, it could only cause spread into where the needle passes through - the skin.. and frankly, that's not really a problem. The cancer spreading to deeper blood vessels and lymph nodes is the problem! So FNAs are often done to determine what a growth may be., and they are a very safe test.
sometimes you see people with a lump they have had for ages and finally get checked only deteriorate after the lump is biopsied!
-- this is because the person had the lump for "ages", and once it got big enough for them to decide to see a doctor, and have it checked, the cancer was quite advanced.
If you have a lump that is growing rapidly, in an awkward spot or is just annoying/doesn't look good - you will likely want it removed anyway, so there is little point going ahead with the FNA. They can remove the whole lump and then test samples to see if it was cancer, and if so, they can arrange further scans etc to see if it had spread. So - if you are happy to put up with the lump, go the FNA. If it's negative, you can just ignore it. If you want it removed either way, might as well just get that done right away.
You'll be injected with local anaesthetic (which stings.. but only for a few seconds!) and then they will do the biopsy. You will feel pressure as the needle goes in, but should not feel any pain. If you feel sharp pain - tell your doctor! Some people need more local anaesthetic than others, so if you tell your doctor you're in pain, he/she can inject a bit more anaesthetic for you. It shouldn't hurt!