AML and ALL differentiating features.

Hello awesomeites !

Today let us find out the difference between AML and ALL on the basis of cell morphology, cytochemistry and immunophenotyping.

So, Acute Leukemia is the presence of blasts >=20% either in peripheral blood or bone marrow.

Myeloblasts in AML and Lymphoblasts in ALL are the two main types. 

Cell morphology:

Myeloblasts:  The characteristic feature is the presence of Auer rods with moderate amount of cytoplasm and cytoplasmic granules and multiple nucleoli

Lymphoblasts:  They have a scanty cytoplasm no granules and nucleoli are not present

Many a times differentiating the two on morphological basis isn’t feasible. So we take the help of cytochemistry.

Cytochemistry:

Myeloblasts:  are myeloperoxidase(MPO) and Sudan black B (SBB) positive

                         Monoblasts which are a part of the myeloid lineage are nonspecific esterase (NSE) positive

Lymphoblasts:  are periodic acid Schiff (PAS) positive

MPO stains the enzyme within the azurophilic granules and is the most specific while SBB stains the lipid membrane of the azurophilic granules and is most sensitive for myeloid differentiation .

Even after this if we aren’t able to differentiate then we take the help of immunophenotyping

 
Immunophenotyping:

It is performed by flow cytometry.

The sample either bone marrow or peripheral blood is stained with antibodies and the cells are allowed to fall freely in a single file across a beam of laser (this is the over simplified version of it :P).

The laser used is Blue laser of wavelength 488nm. When the laser beam hits the cells some of it gets scattered to the sides and is known as the side scatter which is a measure if the granularity of the cells. While the rest of the beams travel in the same line without deviation and is called as the forward scatter and is a measure of the size of the cells.

Neutrophils are the cells with the highest side scatter.

Staining of the cells with antibodies helps in subtyping acute leukemias on the basis of CD markers.

Here is a list of CD markers on varies cells of myeloid and lymphoid lineage

B cell markers:

CD19: present on all B cells

CD10: immature B cells

CD20: mature B cells

T cell markers:

CD3: present on all T cells

CD4 CD8 CD2 CD5 CD7 are some of the other markers present on various T cells

Myeloid markers: CD13 CD33 CD117

Stem cell markers: CD34

Monocyte markers: CD14 CD64

NK cell markers: CD16 CD56

CD45 is present on all leucocytes a.k.a pan leucocyte marker 

That’s all for now, hope this helps in better understanding of AML and ALL!

Keep calm and keep studying!

Stay awesome!

-          Ashish G. Gokhale