Bone marrow morphology predicts additional chromosomal abnormalities in patients with myelodysplastic syndrome with del(5q).

The current World Health Organization classification considers myelodysplastic syndrome with isolated del(5q) a distinct entity owing to its characteristic clinical and pathologic features. Recently, several studies have examined survival, leukemic transformation, and various prognostic factors in these patients. However, there is a lack of detailed comparative pathologic analysis of myelodysplastic syndrome cases in which del(5q) is present in association with additional cytogenetic abnormalities. We studied 26 cases of myelodysplastic syndrome at initial diagnosis with 5q- alone, 5q- plus 1 additional abnormality, and 5q- as part of a complex karyotype. Four of 17 patients had evidence of JAK2 V617F mutation. In contrast to cases of myelodysplastic syndrome with isolated 5q-, patients with additional abnormalities had normal mean corpuscular volume and decreased platelet counts (P < .001). Based on bone marrow examination, they were significantly more likely to have increased cellularity, trilineage dysplasia, lower proportion of small hypolobated megakaryocytes, higher number of blasts, and fibrosis. The presence of these morphologic features can be used to distinguish these more aggressive cases from those with myelodysplastic syndrome with isolated 5q- and a more benign clinical course.