italianburrito,
Your father presumably has a high blast count in his bone marrow as well as in his peripheral blood, and that's part of an MDS diagnosis. Abnormal cell morphology (shape and appearance) are also evaluated.
A certain percentage of MDS patients have normal cytogenetics. According to
this article by Dr. Sekeres at the Cleveland Clinic, it's 20% to 50%, depending on the type of test performed. From the article:
Cytogenetic abnormalities are found in approximately 50% of MDS patients using conventional karyotyping techniques, and in up to 80% using single nucleotide polymorphism array technology.
My wife's situation was different. She was lucky not to have excess blasts (MDS-RA, not RAEB), but unlucky to have abnormal cytogenetics. She was cured by a transplant.
Hearing that your father has a lowered risk level is very positive news. I hope they can get his blast count down with minimal side effects from Vidaza.