Why don't all cases of myelodysplastic syndromes turn into acute myeloid leukemia?

Why don't all cases of myelodysplastic syndromes turn into acute myeloid leukemia?
Do patients who have myelodysplastic syndromes progress to acute myeloid leukemia all have the same type of acute myeloid leukemia?
Genetic Mutations and Cytogenetics Explained: What Patients Need to Know