Posted in Hematopathology

5 Differences between hyper granular (M3) and microgranular (M3v) variants of acute promyelocytic leukemia ( APML)

Differences between hypergranular (M3) and microgranular (M3v) variants of acute promyelocytic leukemia ( APML)

Acute Promyelocytic leukemia is an unique syndrome different from other forms of acute myeloid leukemia (AML).

From clinical symptoms such as disseminated intravascular coagulation (DIC) to unique chromosomal translocation – t(15;17) the list is endless.

Acute promyelocytic leukemia has two common variants- hypergranular (M3) and microgranular (M3v). It is essential to differentate the two variants because of prognostic purposes.

Let’s see a few key 🔑 differences between them.

1.White blood cell counts

M3v, that is the microgranular variant has a higher white blood cell count compared to hypergranular variant (M3).

2. Shape of the nucleus

M3v or the microgranular variety has a bilobed/butterfly shaped nucleus. The hypergranular variant has round to oval nucleus.

3. Auer rods

Auer rods may be present in M3v, but is very less compared to those present in the hypergranular variant. As the name suggests, hypergranular variant has large densely packed granules.

4. Immunophenotyping

HLA-DR and CD34 are often positive in the microgranular variant in contrast to the hypergranular variant.

5. Associated mutations

M3v- microgranular variant is associated with FLT3-ITD mutations whereas, the hypergranular variant (M3) is not associated with FLT3-ITD mutations.

Why should you differentiate?

Presence of high white blood cell counts and FLT3-ITD mutations garner a poor prognosis, hence it is necessary to distinguish between hypergranular variant of APML and microgranular variant of APML.

Classic sliding morphology of microgranular APML blasts with FLT3-ITD mutation.
Courtesy: Society of hemepath page: FACEBOOK

Watch the video for quick summary-

Differences in hypergranular and microgranular variant of APML
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