The myelodysplastic syndromes with excess blasts are broken down into two groups based on the number of blasts in the bone marrow and peripheral blood:
| Criteria | MDS-EB1 | MDS-EB2 |
| Bone marrow aspirate blast count (count>500cells) | 5–9% | 10–19% |
| Peripheral smear blast count (count >200 cells) | 2–4% | 5–19% |
| Auer Rods | absent | might be present |
Some exceptions exist, particularly genetic changes that may put them in Acute Myeloid Leukemia (AML), even if the blasts are slightly fewer than 20% (20% typically places the disorder in the acute leukemia classification). Also, with the 2016 WHO classification, the bone marrow blast count is a percentage of all nucleated cells and is no longer a percentage of just non-erythroid cells. Another thing to note is that fibrosis can occur in the bone marrow in MDS-EB.
Our patient falls into the MDS-EB2 category. Over half of all MDS-EB patients show cytogenetic abnormalities. The most common include: del(5q), -7, del(7q) (our patient), +8, and del(20q). Slightly less than 50% do not have cytogenetic changes but rather various point mutations. Also, cytogenetic abnormalities and point mutations can be found in the same patient.
