AML - NPM1 Mutated:

The immunophenotype is variable. Acute myeloid leukemia with mutated NPM1 can have mainly myeloid blasts or manifests as acute myelomonocytic (see case 3) and monocytic leukemia (see case 2). The myeloid blasts in cases without significant monocytic differentiation are often medium-sized with high NC ratio.

Typical immunophenotype for myeloid blasts (see case 1):

  • Blasts often show expression of CD117
  • CD34 expression is negative or partial variably expressed in a subset of blasts
  • Often bright expression of CD33 and variable (often dim) expression of CD13
  • HLA-DR can be negative in some cases. Such cases may immunophenotypically mimic APL (CD117+, CD34-, HLA-DR-, CD33 bright), but blasts do not show high side scatter as seen in APL and usually do not show CD64 expression.

Case 1: with mainly myeloid blasts; CD117+ blasts in blue; CD34+ blasts in red; monocytes are largely absent.

NPM1_mutated_1 NPM1_mutated_2 NPM1_mutated_3 NPM1_mutated_4 NPM1_mutated_5

Case 2: with mainly monocytic cells at variable stages of maturation; small percentage of CD117+ cells; monocytes in green.

NPM1_mutated_6 NPM1_mutated_7 NPM1_mutated_8

Case 3: with myelomonocytic immunophenotype; CD117+ blasts are largely positive for CD34 in this case; CD117+ blasts in blue; CD34+ blasts in red; monocytes in green.

NPM1_mutated_9 NPM1_mutated_10 NPM1_mutated_11 NPM1_mutated_12 NPM1_mutated_13

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