I'm so sorry to hear this. I know how crushing that news can be. The denial is likely due to one of two reasons.

The review by the physician team led them to determine that Mayo Clinic cannot offer treatment that differs from what you are already receiving. Mayo’s goal is to provide the best care each patient needs, but does not want you to incur additional costs for evaluation or travel if local options are available.

Or it may be that the department has few available appointments. Unfortunately because Mayo Clinic has more requests for appointments than available openings, other factors come into play. Appointments at Mayo Clinic are prioritized on the basis of medical need. Availability depends on the nature and urgency of the problem and Mayo Clinic's ability to help (as determined by a Mayo Clinic physician team).

Did you self refer or did your hematologist make the referral?