Primary myelofibrosis is the most frequent myeloproliferative neoplasm associated with del(5q): Clinicopathologic comparison of del(5q)-positive and -negative cases

Among 23 cases of myeloproliferative neoplasms (MPNs) with an associated del(5q) seen at our institution, 14 (61%) fulfilled diagnostic criteria for primary myelofibrosis (PMF). Other diagnoses included polycythemia vera (PV; n = 2), essential thrombocythemia (ET; n = 1), post-ET myelofibrosis (n = 1), systemic mastocytosis (SM; n = 1), and MPN, unclassifiable (n = 4). Compared to their del(5q)-negative counterparts, del(5q)-positive PMF cases were significantly more anemic (p < 0.001) and thrombocytopenic (p < 0.001). However, survival and leukemic transformation rates appear to be similar between the two groups. del(5q)-positive PMF was histologically characterized by a mixture of both small and monolobated megakaryocytes as well as large and bizarre megakaryocytes. When used, lenalidomide therapy induced hematological and cytogenetic remissions in del(5q)-positive PMF. The current study identifies PMF as another del(5q)-associated myeloid malignancy with characteristic megakaryocyte morphology.