We don't find all monocytic leukemias to be Sudan black B positive,
but I agree that they are usually non-specific esterase positive.
As for our cut-off for calling MPO positive, we use 3% for
cytochemistry and 20% for immunophenotyping; but most cases that are
MPO negative are negative in all of the cells. We use other myeloid
antigen expression, including CD13, CD15, CD33, CD14, CD65 and CD117,
to diagnosis cases as AML that are myeloperoxidase negative and use
the EGIL criteria to diagnose biphenotypic acute leukemia in the
absence of myeloperoxidase. In fact, we do not always look for MPO by
flow in cases that are cytochemistry negative MPO and express numerous
other myeloid-associated antigens in the absence of
lymphoid-associated antigen, because the detection of MPO in that
setting would not alter our diagnosis of AML-M0. Of course, ever lab
develops their own approach to the evaluation of leukemic specimens.
Thanks for your comments.
______________________________ Reply Separator _________________________________
Subject: R:I: Further CD45-negative acute leukemia
Author: Adriano Venditti <avendtti@pelagus.it> at INTERNET
Date: 1/22/98 6:29 PM
I partially agree with you; it is true that some monocytic
leukemia are anti-MPO negative but they are usually positive for non-specific
esterase and more importantly they are sudan B black positive. M0 are, by
definition, negative for cytochemistry. Another point regards the use of cut-off
value to qualify an AML as anti-MPO negative. What are the criteria you use to
distinguish an anti-MPO negative AML from a positive one? We have arbitrarily
set a cut-off value of 10%. Using this value no M0 and a very few monocytic
leukemia were found to be anti-MPO negative. It is obvious that a correct
diagnosis results from the accurate evaluation of data coming from all the
available diagnostic steps.
Da: Daniel Arber[SMTP:darber@smtplink.Coh.ORG]
Inviato: lunedì 19 gennaio 1998 17.13
A: Cytometry Mailing List
Oggetto: Re: I: Further CD45-negative acute leukemia
If you require myeloperoxidase to call a leukemia biphenotypic, you
will miss some cases of mixed lymphoid/ monocytic leukemias. As you
know, some monocytic leukemias are myeloperoxidase negative. As for
AML-M0, we continue to see M0 leukemias that are myeloperoxidase
negative by immunologic methods and would still diagnose them as M0 if
there are other myeloid-associated antigens present and no
lymphoid-specific antigens expressed.
Dan Arber
City of Hope
______________________________ Reply Separator _________________________________
Subject: I: Further CD45-negative acute leukemia
Author: Adriano Venditti <avendtti@pelagus.it> at INTERNET
Date: 1/16/98 7:59 PM
-----Messaggio originale-----
Da: Adriano Venditti [SMTP:avendtti@pelagus.it]
Inviato: venerdì 16 gennaio 1998 19.50
A: Cytometry Mailing List
Oggetto: R:Further CD45-negative acute leukemia
I think we need to have a common language when talking about "biphenotypic
leukemia". This definition, in my opinion is a little bit confusing as it
refers to a broad spectrum of leukemias; from those with a minimal phenotypic
deviation to the so called "genuine" biphenotypic leukemia. The case presented
by Chang sounds like an ALL with phenotypic deviation as suggested by the
expression of CD13 and CD33. On the other hand, the diagnosis of "genuine"
biphenotypic leukemia requires the presence of MPO (as revealed by moabs or at
ultrastructural level) and that of cytoplasmic CD3 or CD22/CD79a. So I would
classified the leukemia presented by Chang as a "genuine" biphenotypic leukemia
if it expressed MPO plus cytoplasmic CD22 or CD79a. At the moment it
remains an
ALL with deviant expression of myeloid antigens. In this view I do not agree
with Daniel when he says that MPO is not essential for the diagnosis of
biphenotypic leukemia. We have, in several publications (Br J Haematol 1994,
Blood 1997, Ann Haematol 1997), demonstrated that indeed it is essential for the
diagnosis of minimal differentiated acute myeloid leukemia (AML-M0) which
sometimes lacks CD13 or CD33. Again, we need a common language and more
importantly, strict criteria to define a biphenotypic leukemia which is, in my
opinion, a different condition than the simple deviant expression of antigens
belonging to other lineages.
----------
Da: Daniel Arber[SMTP:darber@smtplink.Coh.ORG]
Inviato: mercoledì 14 gennaio 1998 22.35
A: Cytometry Mailing List
Oggetto: Re: Further CD45-negative acute leukemia
I would agree that MPO is not essential for a diagnosis of
biphenotypic acute leukemia, but the EGIL scoring recommendation
requires more than two points for myeloid antigens to call a case
biphenotypic. The expression of CD13 and CD33 are worth a total of 2
points and another myeloid marker would be needed before calling the
case biphenotypic.
Dan Arber
City of Hope
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