Clonal evolution in essential thrombocythemia

Essential thombocythemia is a myeloproliferative disorder characterized by an increased production of platelets and marrow megakaryocytes. It is generally believed to be a clonal disorder involving a multipotent stem cell for granulocytes, erythrocytes and platelets. To date, no consistant chromosomal rearrangement has been associated with this disease. We present a case in clonal evolution, having one population of cells with a complex rearrangement involving duplication of chromosome 11 dup(11)(q13q25) in 50% of the dividing marrow population. A second population of cells that evolved from the first population, representing the remaining 50% of the marrow cells, had the derivative 11 with the duplication on the q arm plus an additional translocation with chromosome 17q on the p arm, der(11)t(11;17)(q15;q21) dup(11)(q13q25). Whole chromosome 11 and whole chromosome 17 painting probes (Oncor, Gaitersburg, MD) were applied to verify the 11 duplication and the 17 translocation and to determine the percentage of each clone in the marrow population. It is essential to determine the percentage of each clone to assess disease progression. It is also important to identify the derivative 11 in this case for the myeloproliferative disorders have a tendency to progress to acute nonlymphatic leukemia (ANLL) and the involvement of chromosome 11more » in that disease is well-documented.« less