Clinical importance of bone marrow monocytic nodules in patients with myelodysplasia: retrospective analysis of 21 cases.

Bone marrow monocytic nodules (MNs) can occur in various myeloid disorders. This retrospective review identified 21 patients with myelodysplasia who had unusual and distinct MNs. Eight patients had chronic myelomonocytic leukemia (CMML); 4 had acute myeloid leukemia (AML); and 9 had myelodysplastic/myeloproliferative diseases. In each case, the cells forming MNs expressed strong CD68. MNs appeared to persist even after aggressive chemotherapy, including conventional chemotherapy for 2 AML patients and high-dose chemotherapy preceding allogeneic bone marrow transplantation for 1 CMML patient. Thirteen of 21 patients (62%) died, and acute leukemic transformation was the main cause of death in 3 of 8 patients with CMML. The median survival of the 20 patients with appropriate follow-up was 9.8 months. Our findings demonstrate that MNs are associated with CMML, AML, myelodysplastic syndromes, and myeloproliferative diseases and suggest that MNs are resistant to intensive chemotherapy and patients with bone marrow MNs have a poor prognosis.