Acute myeloid leukaemia (AML) with mutated NPM1 carries mutations that usually involve exon 12 of NPM1. Here are some key points to remember.
1. There is a female predominance in this type of AML.
2. There is a strong association between both acute myelomonocytic and acute monocytic leukaemia and NPM1 mutation.
3. Charactistic cup-shaped blasts are seen.
4. Immunophenotype: AML with mutated NPM1 is characterized by high CD33 expression and variable (often low) CD13 expression.
5. Immunophenotype: KIT (CD117), CD123, and CD110 expression are common.
6. Immunophenotype: HLA―DR and CD 34 is often negative.
7. Two major subgroups of AML with mutated NPM1 have been described: one with an immature myeloid immunophenotypic profile and one with a monocytic (CD36+, CD64+, CD14+) immunophenotypic profile.
8. Immunohistochemical detection of cytoplasmic NPM1 is predictive of NPM1 mutations. Remember that normally NPM-1 is expressed as nucleolar positivity.
9. Cases with a normal karyotype, in the absence of FLT3―ITD mutation, have a characteristically favourable prognosis.
10. AML with mutated NPM1, normal karyotype and absence of FLT3 internal tandem duplication mutation has characteristically favorable prognosis
Additionally According to WHO 2022- 5th edition this is one of the Acute myeloid leukemias which can be diagnosed irrespective of blast count.
What are the subtypes of AML which do not require blast count of 20 %
REFERENCES
- Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. 5th ed; 2022.
- Falini B, Nicoletti I, Martelli MF, Mecucci C. Acute myeloid leukemia carrying cytoplasmic/mutated nucleophosmin (NPMc + AML): biologic and clinical features. Haematologica. 2007;92(4):519-532. Available from: https://haematologica.org/article/view/4404
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