Nightly News | January 23, 2014
>>> finally tonight, they were already best friends , two boys in first grade, they were all but inseparable, and like all best friends everywhere, when something went wrong they had each other's backs. we learned about their story from st. louis, and tonight, nbc's rehema ellis has their remarkable story.
>> reporter: vincent butterfield and jack gossick are best friends in missouri with a very special bond. sure, they play. and tell silly jokes.
>> why does the chicken cross the playground.
>> reporter: the answer?
>> to get to the other side.
>> reporter: but in all the child's play, they're teaching a very grown-up lesson about the power of friendship. last june, zach was diagnosed with an acute form of leukemia.
>> as a parent you want to make sure nothing bad ever happens to your child and when something does, you want to be able to fix it and i couldn't. and it was horrible.
>> reporter: despite frequent trips to the hospital he continued going to school.
>> he is the strongest kid that i know.
>> reporter: vincent stayed by his side, learning all about his friend's cancer.
>> it is when the white blood cells and the red blood cells fight.
>> reporter: vincent wanted to help.
>> i took some yarn, then crocheted, he knitted scarves and gave the money to me.
>> reporter: he raised about $200, and then vincent did something else.
>> he came in and had a cap on and said i have a surprise, he pulls off his stocking cap and here i see he shaved his head.
>> reporter: he didn't want zach worried about what others might say.
>> and it made zach feel like he is not the only one without any hair.
>> reporter: zach 's cancer is in remission now. as for their friendship?
>> a beautiful thing.
>> reporter: a beautiful thing. they say will last a very long time.
>> i would say forever.
>> like a bff?
>> reporter: rehema ellis, nbc news, new