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9 - Grade/differentiation unknown, not stated, or not applicable
Juvenile chronic myelomonocytic leukemia
A rare form of childhood leukemia in which cancer cells often spread into tissues such as the skin, lung and intestines.
JMML is a clonal hematopoietic disorder of childhood that is characterized by proliferation principally of the granulocytic and monocytic lineages. Erythroid and megakaryocytic abnormalities frequently present, in keeping with evidence that JMML arises from a BM stem cell with multilineage potential in the myeloid series.
The peripheral blood and bone marrow are always involved; proliferation of the granulocytic and monocytic lineages. Blasts plus promonocytes account for <20% of PB and BM. Leukemic infiltrates are common in the skin. The physician will test to confirm that the Philadelphia chromosome and the BCR-ABL1 fusion gene are absent. Most patients present with constitutional symptoms or evidence of infection. There is generally marked hepatosplenomegaly. Occasionally spleen size is normal at diagnosis but rapidly increases thereafter. Although JMML rarely transforms into Acute leukemia, it is a rapidly-fatal disease for most children if left untreated. The median survival time without allogeneic stem cell transplant is about one year. In the absence of effective treatment most children die from organ failure, such as respiratory failure, due to leukemic infiltration. Stem cell transplant can cure about half of the patients.