My Brother Can't Be Sick.

My brother didn't even tell me.  My  mother did.  She called to update me because my brother is dealing with it his own way.  He's acting like it's nothing.  Like it can't even turn out to be something.  He's joking about it, and laughing, and I get why he is doing it, but I don't know why he didn't tell me?
My brother is one of my best friends.  He is 30, has 2 little girls and a wife.  Lately he has had some issues with blood clots in his legs and has had to inject blood thinners into his stomach.  He was off work for awhile.  Then they sent him for a look at his chest, to check his heart due to all this blood clot jazz. 
And they found a mass on his lungs.
He has smoked since he was 14.  But he is in the process of quitting.  Before all this.  He has an RX for Champex, and he was going to get it at the end of this month, that's when his coverage would pay for it.
He just went for another test.  It could be nothing.  It could be something simple like a cyst that they can remove with surgery. 
Or it could be cancer.
My brother, my best friend, could be dying.  And he didn't even tell me. Our mother did.  He kept it a secret!