Thrombocytosis as a Presenting Feature in Myelodysplastic Syndromes (MDS) in Adults - 40 Year Experience from a Single Institution in the USA.

Thrombocytosis at presentation is uncommon in the myelodysplastic syndromes (MDS), and its influence on the clinical course of the disease and on prognosis is uncertain. To determine the clinical course and long-term outcomes of patients (pts) with thrombocytosis at initial diagnosis of MDS, we conducted a retrospective analysis of 503 pts diagnosed with MDS between Jan 1966 and July 2006 at the Minneapolis VA Medical Center. Original bone marrow and peripheral blood slides and reports were reviewed with a hematopathologist (H.M.) in all pts with high platelet counts (> 400 × 10³/μL) and evidence of dysplasia. Clinico-pathological correlation was obtained by chart review. Patients with inadequate data, secondary causes of thrombocytosis, transient thrombocytosis, and those without evidence of dysplasia were excluded. Of 503 pts, 41 (8.2%) were found to have thrombocytosis at presentation. Their median age was 74 years. The spleen was enlarged (by imaging) in 6 pts. Peripheral blood counts (mean; range) at diagnosis were: hemoglobin (10.9 g/dL; 7.4 – 17.1), absolute neutrophils (7.9 × 10³/μL; 0.8 – 30.7) and platelets (627 × 10³/μL; 402 – 1231). The cases were re-classified according to the WHO classification of myeloid disorders as follows: chronic myelomonocytic leukemia-1 (CMML-1) = 17 (41%), refractory anemia with ringed sideroblasts and thrombocytosis (RARS-T) = 13 (32%) and others = 11 (27%; including 2 pts each with RA, MDS/myeloproliferative disorder-unclassified [MDS/MPD-U] and 5q- syndrome, and 1 pt each with RA with excess blasts [RAEB-1], therapy related MDS [tMDS], refractory cytopenia with multilineage dysplasia [RCMD], MDS-U and atypical chronic myeloid leukemia [Aty CML]). Bone marrow fibrosis was increased in 3 pts with CMML-1 and 1 with RARS-T, and was normal or only focally increased in all other pts. The IPSS risk category was Low in 15 pts, Int-1 in 3 pts and Int-2 in 2 pts. Cytogenetic data was not available in the other pts. Jak-2 mutation analysis was positive in 2 pts with RARS-T, negative in 1 pt each with RARS-T and MDS/MPD-U, and is pending in others. On follow-up, 2 pts with CMML-1 and 1 pt with Aty CML transformed to acute myeloid leukemia (AML) and both pts with 5q- syndrome transformed to CMML-2. Two pts with RARS-T progressed to RAEB-2 and 1 pt with CMML-1 progressed to CMML-2. One pt with CMML-1 developed marked myelofibrosis. Marked thrombocytosis required hydroxyurea treatment in 5 pts. One MDS-U pt received 5-azacytidine. Four of 41 (10%) pts experienced major bleeding events; 3 were receiving aspirin. Five pts required ongoing red cell transfusions. The median survival (MS) was 36 months in RARS-T, 60 months in CMML-1 and 27 months in others; the MS of all 41 pts was 48 months. Causes of death were AML in 3 pts, cytopenias due to MDS in 6 pts and unrelated/unknown in 21 pts. Eleven pts are currently alive. In conclusion, the majority of pts presenting with myelodysplasia and thrombocytosis fall in the MDS/MPD category of the new WHO classification (most commonly CMML or RARS-T), be older, and have low-risk features (IPSS Low or Int-1). The risks of spontaneous bleeding, transformation to AML, progression of disease or myelofibrosis are low, and the overall prognosis is relatively favorable. Platelet counts may reach levels requiring cytoreductive therapy. This study helps better understand the natural history and prognosis of this varied spectrum of MDS and overlap syndromes.