my dad got diagnosed with an extremely rare blood cancer

he has only just turned 59 an d has been diagonsed with something called systematic  mastocytosis they have said its extremely rare and there is no treatment that can help i am so devestated my dad is my world he has brought me up all on his own since i was 4 ive now just turned 26 and have 2 kids his grandkids love him so much   how do i cope my dad says he has come to terms with it but dnt mean i have.