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9 - Grade/differentiation unknown, not stated, or not applicable
This leukemia meets the criteria for assignment to both T and myeloid lineage, but in which blast lack genetic abnormalities. Most cases have blasts with no distinguishing features, morphologically resembling ALL, or have dimorphic populations, with one resembling lymphoblasts and the other resembling myeloblasts
(This code is effective for cases diagnosed 2010 and later. For cases diagnosed prior to 2010 see code 9801/3.) Although this leukemia meets the criteria for assignment to both T and myeloid lineage, the blasts lack the genetic abnormalities. This is a rare leukemia accounting for less than 1% of leukemias. It is relatively more frequent in children but is seen in both children and adults. There are no unique clinical features for this leukemia.