45
OCTOBER 16-18, 2011 • PORTLAND, OR
P9
A Scoring System for Immunophenotypic
Distinction between Acute Myelogenous Leukemia
with Thymic Markers [AML(T)] and T-Acute
Lymphoblastic Leukemia with Myeloid Markers
[T-ALL(M)] Using a Primary Antibody Panel
Amar Dasgupta, Vishal Mehrotra, Archana Vazifdar,
Manisha Ramani
Sections of Hematology & Flow Cytometry, Super
Religare Laboratories, Mumbai, India
Blasts in 20-40 % cases of AML and in 20-30%
cases of T-ALL express T-lymphoid and myeloid
antigens respectively, causing diagnostic dilemma.
The high cost of a step-wise immunophenotyping of
hematolymphoid neoplasms prompted us to develop a
scoring system for clear distinction between these two
entities based on the antigenic features of these cells
using a primary antibody panel. One thousand eight
hundred seventy-four cases of acute leukemia were
immunophenotyped using a comprehensive panel of
antibodies. Cytochemical MPO was tested in all cases
expressing translineage markers while cytoplasmic (c)
CD3 and cMPO were checked in 40/187 (21%) these
cases for confrmation of T-lymphoid and/or myeloid
phenotype respectively One hundred forty-four out of
791 cases of AML (18%) and 43 out of 128 cases of
T-ALL (34%) showed the presence of T-lymphoid and
myeloid markers respectively. “Myeloid” phenotype of
blasts in AML(T) was suggested by HLA-DR positivity
(135/144, 94%) (Score 1); CD117 expression
(127/144, 88%) (Score 0.5); CD13 (131/144, 91%)
(Score 1) and absence of CD5 (140/144, 99%) (Score
1) and of CD10 (142/144, 99%) (Score 1). In contrast,
“T-lymphoid” phenotype in T-ALL(M) was indicated
by normal intensity CD45 expression (100%), HLA-
DR negativity (33/43; 77%), CD5 expression (28/43;
65%) and a high incidence of CD 13 negativity (35/43;
81%). All cases of AML(T) yielded a score of =/>4.5
while it was =/<3.5 for T-ALL(M) cases. Cases of true
mixed lineage (myeloid/T-lymphoid) leukemia had
a score between 3.5 and 4.5. The above approach
represents a more objective and accurate system for
distinguishing AML(T) from T-ALL(M).
POSTER ABSTRACTS