Tiny buttons like that are a pain when dialing and texting. I have the t290a phone and the buttons are INCREDIBLY SMALL!!!
The whole brain tumor thing is so old, the likeliness of you getting a tumor BECAUSE of your cell phone is next to impossible. If you ALREADY have a tumor it's a bit different I think. If you don't have brain tumors...I wouldn't worry at all.
http://www.nokiausa.com/phones?showp...tby=1&resort=1 - Have a look there, they make many non-flip style phones. I'm thinking about getting one as well...