Honestly, no.
( 1 ) It's self expression to let go of pressure and stress. It's better to say rather than do something physical.
( 2 ) It wasn't insulting. Yeah, you insulted cancer, but you basically said, "cancer is bad", which is good.
( 3 ) With parenting, you aren't supposed to yell at your kids so suddenly for something that small.
But, besides that, she's not completely in the wrong, though. You shouldn't swear, just, because swear words have a special magic to them to instantly offend, worry and anger people who come in contact of hearing or seeing them, whether they're used in that way or not. To use swear words, you can't throw them around so easily like that or else something worse could happen besides your mom yelling at you. But, beyond that, you should take it down just so your mother doesn't get more angered and feel forced to unleash worser punishment. Don't think of it as a loss, just think of it as you being the better person, seeing that your mom can't control herself, possibly, due to stress from her job and work at home, so you have to be the better person and act calm for the both of you.