Myeloid/Leukemia confusion

[bdc142]

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Hi all,
I'm getting very confused about 'myeloblasts'.

1) Pathoma classifies 'myeloblast' as the progenitor of neutrophils, basophils, and eoisonophils and 'monoblast' as the progenitor for monocytes/macrophages. However, Sattar also says/contradicts himself by saying that GM-CFU or G-CFU can be used as a treatment for neutropenia (implying that monocytes + granulocytes have a common progenitor)
2) Goljan has a chart in his book (pg 280 4e), where there is no myeloblast at all, and where GM-CFU gives off to both neutrophils AND monocytes (implying a different classification than Pathoma...see point 1)
3) Robbins (pg 591) does not have a myeloblast at all, and has a different lineage of hematopoieses than both Goljan and Pathoma!

Can anyone clarify this term for me? And especially in regards to myeloblastic leukemias / disorders? Are myeloproliferative disorders referring to the 'myeloid stem cell' or 'myeloblast' (whatever this is)? Why does AML refer to 'myeloblast' if it has subtypes involving megakaryoblasts (M7)? Shouldn't myeoblast only refer to granulocytes?

Any help is appreciated! I'm dying here.

 

[Ionian]

I had wrote a document in which I corrected errors I found in robbins, and Saters books/videos.

Lucky you I covered this point. Satter sent me an email back and approved the following; (read in full and I believe it will give you some clarity!!)



3. Clarification: Acute Myeloid Leukemia (AML) is neoplastic accumultation of Myeloid Blasts in the bone marrow.

“Blasts” are precursor cells in the bone marrow.

“Myeloid Blasts” are thus any precursor cells of the Myeloid Stem Cell Line. (see below)

Myeloblasts specifically refer to precursor cells destined to become Promyelocytes, and subsequently Granulocytes.


· Robbins Basic Pathology (9th ed.)

Chapter 11. Page 444.

“By definition, in AML myeloid blasts or promyelocytes make up more than 20% of the bone marrowcellular component. Myeloblasts (precursors of granulocytes)… etc.”



· Pathoma [pg 56 2nd edtion, terms have been updated in the new edition, videos and discussion (below) remain valid]

Chapter 6. White Blood Cell Disorders. Pg 54. III. Acute Myeloid Leukemia

“A. Neoplastic Accumulation of myeloblasts (>20%) in the bone marrow.” [1st edition only]


Potentially confusing, as this seems to say all AMLs will give rise to a proliferation of pre-granulocytes. It’s important to make the distinction because AMLs can be subclassified by those cell types which are Myeloperoxidase + (if originating from Myeloblasts) or MPO- (arising from other blasts lines). This entry in pathoma might seem to say then AML is solely due to a proliferation of granulocyte precursors, thus AML is always MPO+, which is not the case.


On Quotes from the “Acute Leukemia” Video: [Still relevant to the current videos]

i. In this beginning of this video he reviews hematopeoisis with a drawing, and specifically says “myeloid blast” and subsequently uses the term interchangeably (i.e., incorrectly) with “Myeloblasts”, but occasionally emphasizes “Myeloid…Blast” again.


ii. “One of the key markers for a Myeloid Blast is the presence of myeloperoxidase”

It should be noted that the myeloperoxidase reaction is useful in distinguishing AML from ALL, but many subtypes of AML are infact MPO-. M2/M3 or “AML with maturation” and “Acute Promyelocytic” respectively are the only MPO+ AMLs. (This is also made clear in Rapid Review pathology 3rd Edition Revised Reprint pg. 234)


Pay close attention to his slides as which continually switch between “Myeloid Blasts” and “Myeloblasts” and make the appropriate distinctions given above. At one point he does correctly associate MPO+ with “Myeloblasts” (and not Myeloid Blasts) on his slides.


Bottom Line: “Myloid-Blasts” are precursors to many linages giving rise to Myeloblasts (pre-granulocytes) or Megakaryoblast (pre-megakaryocyte) for example.


Note: Another Potential point of confusion arises in the contex of “Acute Myeloblastic Leukemia” in this form “Myeloblastic” is colloquial for Myeloid Blasts (and not Myeloblasts as it may seem).

Acute Myelogenous Leukemia = Acute Myeloid Leukemia =Acute Myeloblastic Leukemia


To Further Confuse you: Note that in Chronic Myelogenous Leukemia (CML), Myeloblasts (pre-granulocytes) become MPO-, i.e. they lack Auer Rods.

 

[bdc142]

Lonian, thanks! That helped explained it! Those darned scientists and their terrible naming scheme -_-

Any chance I could get a hold on that document where you corrected those errors? I'd really appreciate it!