Have A Diagnosis Code D72.819 Decreased WBC Count Unspecified, Medical

have a diagnosis code D72.819 Decreased WBC count Unspecified, medical is /primary MD sending me to a oncologist which I thought was a doctor of studing tumors Primary never said anything to me be an apt person called up to make an appt. with me WHY what are they looking for? I'm scared
I don't have the money on s.s.i. 500 for the month I'm sorry to have brothered you with my question I will what till I can call them on Monday and say whats going on!!!!! thank you any way.