Posted in Hematopathology

10 Key points to remember in NPM-1 mutated AML (Acute myeloid leukemia)

Acute myeloid leukaemia (AML) with mutated NPM1 carries mutations that usually involve exon 12 of NPM1. Here are some key points to remember.

10 Key points to remember in NPM-1 mutated AML (Acute myeloid leukemia)
Cup shaped blasts in NPM-1 mutated AML

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 character­ ized by high CD33 expression and vari­able (often low) CD13 expression.

5. Immunophenotype: KIT (CD117), CD123, and CD110 expres­ sion are common.

10 Key points to remember in NPM-1 mutated AML (Acute myeloid leukemia)
Immunophenotyping of AML with NPM-1 mutations

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.

A diagnostic algorithm to diagnose AML with NPM-1 mutations. Cytogenetic testing is performed when cytoplasmic staining is observed (30-35%)

9. Cases with a normal karyotype, in the absence of FLT3―ITD mutation, have a characteristically favourable prognosis.

10. Co-occurrence of NPM1, FLT3-ITD, and DNMT3A muta­ tions has been associated with a particu­larly poor outcome.

Hope you remember these key points for your boards!