Vol 43 # 2 June 2011 - Kma.org.kw

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Pattern of Chromosomal Abnormalities in Pediatric Acute Lymphoblastic Leukemia (ALL)
June 2011
Fig. 3: G-Banded male karyotype in ALL patient showing multiple
whole chromosomal deletions such as deletion of Chr 2, 3, 4, 12, 13,
15, 16, 17&Y (arrow). This is an example of numerical chromosomal
abnormality in ALL [37, X, hypodiploidy and aneuploidy] (G-T-G
Banding, 40X).
cytogenetic techniques such as fluorescence in-situ
hybridization (FISH). The FISH technique have become
an integral part of cytogenetic analysis and must be
regarded as complementary, not replacement tools [27,
28]
.
The t (12; 21) (p13, q22) is the most common
structural abnormality among pediatric B - ALL and
carries a favorable prognosis. However, this can be
missed by routine low resolution G-banding technique
and hence remain cryptic [8] . In a recent study, by using
conventional cytogenetics and FISH technique [28] , t (12;
21) (q13; q 22) was found to be the most common (22%),
followed in frequency, by 9p abnormalities (10%), t
(1;19) (8%), t (9; 22) (8%), and 11q23 abnormality (5%).
Rare translocations such as t (5;12), t (14,19), t (12;16),
Fig. 4: Metaphase spread of chromosomes in a male child with
ALL showing altered chromosome 22 following translocation
[Philadelphia chromosome (Ph1) (arrow)] (46, XY). Detailed
structural abnormalities of chromosome 9 is not appreciated at this
resolution (Giemsa stain, 40X). Due to low resolution GTG banding
technique, Ph1 chromosome may be missed in up to 2-3% cases.
der (1) t (1,12), and t(5,15) were the rare structural
abnormality noted. Comparable to our observations,
translocation t (9; 22) was the most common structural
abnormality detected in other studies from Taiwan
and India [14, 29, 30] .
Barring the age factor, clinical parameters
such as male gender, organomegaly, high TLC,
thrombocytopenia, and ALL-L2 phenotype were
more common in our patients at the time of first
admission. These findings were in accordance with
poor cytogenetic parameters such as hypodiploidy
and translocations [t (10; 14), t (9; 22), etc] and thus,
predictive of adverse outcome in our study.
The mechanism of various numerical abnormalities
in leukemia is complex and least understood [31] .
Fig. 5: G-Banded karyotype in a female child of ALL showing primary
structural abnormality in the form of translocation between long
arms of chromosome 9 and 22 [t (9; 22)] (arrow). The chromosome 22
after the rearrangement is known as the Philadelphia chromosome
(46, XX, G-T-G Banding).
Fig. 6: Secondary chromosomal abnormalities in ALL blasts
characterized by stickiness between the chromosomes leading
to poor quality of chromosome separation by hypotonic saline
treatment during routine G-banding technique (Giemsa, 40X)