Near-Triploid and Near-Tetraploid Acute Lymphoblastic Leukemia of Childhood
By Ching-Hon Pui, Andrew J. Carroll, David Head, Susana C. Raimondi, Jonathan J. Shuster, William M. Crist,
Michael P. Link, Michael J. Borowitz, Frederick G. Behm, Vita J. Land, Michael B. Nash,
D. Jeanette Pullen, and A. Thomas Look
Cytogenetic and DNA flow cytometric analyses of leukemic
cells from 1,971 children with newly diagnosed acute
lymphoblastic leukemia (ALL) identified stem lines with
modal chromosome numbers greater than 65 in 26 patients
(1.3%). Near-triploidy (66 to 73 chromosomes) was found
in six cases and near-tetraploidy (82 to 94 chromosomes)
in 20. A striking morphologic finding was the presence of
clumped chromatin with grooved nuclei or Rieder cell
formation in 20 cases. Other than a slight excess of the
pre-B immunophenotype, the near-triploid cases did not
appear to differ substantially from the general ALL population in clinical features. In contrast, near-tetraploid cases
were more often associated with a T-cell immunopheno-
type (47% v 14%. P < .001) and L2 morphology (30% v
22%. P < .01),and were older at diagnosis (medianage, 8.6
Y 4.8 years, P = .01) than cases with other ploidies.
Moreover, an unusually high proportion of near-tetraploid
cases tested (6 of 15) expressed one or more of the
myeloid-associated antigens CD13, CD15, and CD33. Despite the use of contemporary intensive chemotherapyand
short follow-up for most patients, 6 of the 20 neartetraploid cases have relapsed or died. This study suggests
that the near-tetraploid subtype differs from other cases of
hyperdiploid >50 ALL, which have been associated with a
favorable prognosis.
0 1990 by The American Society of Hematology.
B
admitted to Total Therapy Studies X and XII6 at St Jude Children’s
Research Hospital (SJCRH; Memphis, TN) between 1981 and
1988, and 1,369 were enrolled in Pediatric Oncology Group (POG)
studies 8602” and 8704” from 1986 to 1989. Bone marrow
specimens from patients enrolled in the POG studies were shipped to
the University of Alabama at Birmingham (UAB) for chromosome
analysis and to SJCRH for flow cytometric studies. All patients were
advised of the procedures and their attendant risks, in accord with
institutional guidelines; informed consent was obtained in each
instance.
LAST CELL PLOIDY A N D D N A content have important prognostic implications in childhood acute lymphoblastic leukemia (ALL).’ Of the major ploidy subgroups
studied to date, A L L with hyperdiploidy >50 chromosomes
has the most favorable prognosis.*-’ Modal chromosome
numbers of hyperdiploid >50 A L L cases are tightly distributed around a median of 55.’ Cases with more than 65
chromosomes are rare, and the clinical characteristics and
treatment outcome of near-triploid or near-tetraploid ALL
have been described only in single case report^.^.'^ With the
use of cytogenetic and DNA flow cytometric analysis in a
large cohort of children with newly diagnosed ALL, we
identified 26 cases that had a leukemic stem line with greater
than 65 chromosomes. Our study suggests that neartetraploid cases represent a unique subgroup of ALL, characterized by a preponderance of T-cell immunophenotype,
specific morphologic features, and, possibly, a poorer prognosis.
MATERIALS AND METHODS
Blast cells from a total of 1,971 patients with ALL were
successfully studied for their karyotype. Of these patients, 602 were
Blast Cell Morphologic Studies
Cases were classifiedaccording to French-American-British (FAB)
criteria,” based on bone marrow cell morphology and cytochemical
staining characteristics. Because FAB classification was not available for the cases with other ploidies admitted during the same
period, we compared the distribution of L1 versus L2 in neartetraploid cases with that among children enrolled in POG clinical
trial ALinC 13. Wright-Giemsa-stained slides were also reviewed
for the percentage of large blasts (defined by size twice that of a
small lymphocyte); the presence of clumped chromatin; irregularly,
partially or completely (Rieder cell) cleaved nucleus (greater than
10%of cells); and vacuolated cytoplasm (greater than 3 vacuoles per
cell in greater than 20% of cells).
Blast Cell Immunophenotyping
From the Departments of Hematology-Oncology and Pathology
and Laboratory Medicine. St Jude Children’s Research Hospital;
the Department of Pediatrics, University of Tennessee, Memphis,
College of Medicine; and the Pediatric Oncology Group, St Louis,
MO.
Submitted January 19, 1990; accepted April 4, 1990.
Supported in part by the following grants awarded by the
National Cancer Institute: CA-20180, CA-21765, CA-31566, CA05587, CA-15525, CA-30969. CA-15989. CA-21939, and CA33603, and by the American Lebanese Syrian Associated Charities
(ALSAC).
Address reprint requests to Ching-Hon Pui, MD, Department of
Hematology-Oncology, St Jude Children’s Research Hospital, 332
N Lauderdale. PO Box 31 8. Memphis. TN 381 01.
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be hereby marked
“advertisement” in accordance with 18 U.S.C.section I734 solely to
indicate this fact.
0 I990 by The American Society of Hematology.
0006-4971f9Of7603-0018$3.00/0
590
Bone marrow cells were separated on a Ficoll-Hypaque gradient.
Immunophenotyping was performed in three separate laboratories
(SJCRH; Stanford University School of Medicine, CA; and Duke
University Medical Center, Durham, NC) using slightly different
panels. Cell-surface antigens were detected with a standard indirect
immunofluorescenceassay using monoclonal antibodies (MoAbs) to
lymphoid-associated antigens, including CDl, CD2, CD3, CD4,
CDS, CD7, CD8, CDlO (common ALL antigen, CALLA), CD19,
CD20, CD21, and CD22, and to myeloid-associatedantigens (CD13,
CD15, and CD33). Cells were also tested for surface (sIg) and
cytoplasmic immunoglobulin (cIg). Cells were analyzed for fluorescent activity by fluorescencemicroscopy or flow cytometry. Lymphoblasts were classified as T (CD2+, CDS+, CD7+), B (sIg+), pre-B
(cIg+), or early pre-B (CD19+ and/or CD22+, CD2-, CDY,
CD7-, clg-, sIg-), as previously
Chromosome Analysis
Bone marrow samples from the patients studied at SJCRH were
processed immediately after collection by the direct method of
B h d , VOI 76,
N O 3 (August 1). 1990: pp 590-596
59 1
NEAR-TRIPLOID AND NEAR-TETRAPLOID ALL
Williams et
Samples from POG institutions other than SJCRH
were placed in RPMI 1640 supplementedwith 15%fetal calf serum
and shipped overnight to the UAB cytogenetic laboratory. On
arrival, samples were placed in short-term (24-hour) cult~re.~’
Routine methods were used for culture harvest, slide preparation,
and GTG-banding. Chromosome abnormalities were classified according to the International System for Human Cytogenetic
Nomenclat~re.’~
DNA Content Determination
Leukemic marrow samples were stained with a DNA-specific dye,
propidium iodide, and analyzed by flow cytometry, as previously
de~cribed.,~
Results were expressed as the DNA index (ratio of
DNA content in leukemic Go/G, cells to that in normal diploid
G,/G, cells), a measure that correlates closely with chromosome
number. Multiple leukemic lines within a single case were arbitrarily
designated first and second, based on DNA content per cell (lowest
content = first line). The percentages of cells in the Go/G,, S , and
G, + M phases were determined by analyses using the computer
program PEAK.26In cases with two leukemic lines, the percentage of
S phase was determined for the higher ploidy line.
Statistical Analysis
Differences in the distribution of clinical and biologic features
between near-tetraploid cases and those with other ploidies were
tested by the two-tailed Fisher exact test or the Pearson chi-square
test for categorical variables, and by the Wilcoxon test for continuous variables. Correlation between the percentages of large blasts
and of blast cells in S phase among near-tetraploid cases was tested
by the Spearman rank-order analysis.
RESULTS
Of the 1,97 1 cases studied, 26 (1.3%) were found to have a
leukemic stem line with greater than 65 chromosomes by
karyotypic analysis or flow cytometry. In three of the 24
cases in which hyperdiploidy >65 was identified by chromosome analysis, flow cytometry was not performed (see Table
1). There were two cases in which the near-tetraploid line
was detected by flow cytometric analysis, but karyotypic
study showed only residual normal cell metaphases. Among
the remaining 21 cases, the D N A index and the karyotype
ploidy determination were closely correlated.
For comparison of cytogenetic and clinical features, the 26
cases were divided into two subgroups: near-triploid (66 to 73
chromosomes, cases 1 through 6) and near-tetraploid (82 to
94 chromosomes, cases 7 through 26).
Karyotypic Findings
Near-triploid subgroup. The modal chromosome number of the leukemic cell lines in these six cases ranged from
66 to 73. One case (no. 3) had two abnormal leukemic lines
detected by flow cytometric analysis. Structural chromosomal abnormalities were noted in 4 of the 6 cases. Every
chromosome was involved in trisomies, and some in tetrasomies (numbers 8, 10, 11, 14, 18, 21, and sex chromosomes).
Five copies of chromosome 21 were found in two cases and
six copies in another case.
Near-tetraploid subgroup. The modal chromosome num-
bers in these 20 cases ranged from 82 to 94. By flow
cytometric analysis, 11 cases were found to have two leukemic cell lines. Tetrasomies most often involved chromosomes
5, 8, 10, 11, 12, 18, 19, 20, 21, and sex chromosomes. More
than four copies of chromosomes 3 , 5 , 7 , 8 , 17,19, or 21 were
found in some cases. Of the 10 well-banded cases, structural
chromosomal abnormalities were identified in 9, including
deletions in 6 cases and translocations in 5. Nonrandom
chromosomal abnormalities consisted of del(6q) in three
cases, del(9p) in two, and t(4;11)(q21;q23) in one. Of the
nine identified cases with structural chromosomal abnormalities, six had paired chromosomes containing the same
rearrangements or deletions.
Morphologic Findings
Near-triploid subgroup. Bone marrow slides were adequate for review in 5 of the 6 near-triploid cases. Four of
these five cases had cleaved nuclei with clumped chromatin
and two had vacuolated cytoplasm; only one had L2 morphology, and none contained more than 50% large blast cells
(Table 2).
Near-tetraploid subgroup. Among the 20 near-tetraploid cases, cleaved nuclei were noted in 17 cases, clumped
chromatin in 16, vacuolated cytoplasm in 6, L2 morphology
in 6, and greater than 50% large blasts in 4. The typical
findings of cleaved nucleus with clumped chromatin are
depicted in Figs 1 and 2. The frequency of L2 morphology in
the near-tetraploid cases was significantly higher than that in
other ploidy groups (30% v 22%, P < .01). The L2 blasts
were characterized by low nuc1ear:cytoplasmic ratio and
irregular nuclear shape in all 6 cases, large cell size in 3, and
prominent nucleoli in 2. As expected, L2 cases had significantly higher percentages of large blasts than L1 cases
(median, 52.5% v 13.5%, P = .02). The percentages of blast
cells in S phase did not differ significantly between the L1
and L2 cases (median, 7.3% v 12.7%, P = .23); however, the
percentage of S phase was determined in only three L2 cases.
There was also no correlation between the percentages of
large blasts and the proportion of blasts in S phase in the
near-tetraploid cases (n = 17, r = .2, P = .43).
Clinical Characteristics and Treatment Outcome
Near-triploid subgroup. The three boys and three girls
ranged in age from 2.0 to 11.2 years a t diagnosis (median, 4.5
years). Leukocyte counts ranged from 3 to 38 x 109/L
(median, 11.5 x 109/L); platelet counts from 49 to
320 x 109/L (median, 144 x 109/L); and hemoglobin levels
from 6.3 to 11 g/dL (median, 7.5 g/dL). None of these
patients had a mediastinal mass or central nervous system
(CNS) leukemia at diagnosis. Early pre-B and pre-B ALL
were each found in three cases. None of the five cases tested
(nos. 1 to 5 ) expressed myeloid-associated antigens. All six
patients remain in continuous complete remission from 1 + to
3 1+ months. The number of near-triploid cases was too
small for meaningful statistical comparisons with cases of
other ploidies.
Near-tetraploid subgroup. The 12 male and 8 female
patients ranged in age from 2.8 to 19.2 years (median, 8.6
Age
(y)
3.4
4.3
11.2
2.0
7.0
2
3
4
5
6
W
2.8
13.8
7.4
10.6
16
17.
18
19
+
+
46.XY171
3.0
90
CALLA+ T cell
118
W
6.6
26
46,XX(81
3.6
1.93 (80)
95
CALLA+ pe-8
71
6
7
9
1.87 (26.71, 2.08 (52.91
+
+
+
+
+
93,XY. 7( 19)/46,XY(1I
IF
Death
CNS
+
5+
5+
43
30+
0
8
lo+
1+
13+
22
*PIoddy numbsr repatad p a v ~ o ~ s l y . ~
Abbreviations: W. white: H. hispanic: 0.oriental: 8, black: M, male: F. famals: CALLA, common acute lymphoblastic leukemia antigen: NO. not dona: 7. not interpretable: CNS. central newous system relapse: EM. bone marrow relapse: N. nodal relapse: IF, inductionfailwa.
2
22
F
W
4.8
25
94,XY.+X.+V,+ 1,+ 1 . + 2 . + 2 . + 3 . + 3 . + 3 . + 4 . + 4 , + 5 , + 5 , + 6 . + 7 . c 8 9 , + 1 0 ,
+lo,+ 11,+ 11.C 13.+ 14.C 15.C 16.+ 16.+17.+ 1 7 . f 1 6 . t 18.+ 19.+ 19.+ 19,+20.
+20, 2 1,+21, +22. +4f. +de1~2~1p21~,+2der112~t~12:71~~13:7~~15~/46,XY~3~
0.8
2.02 1801
90
CALLA+ pre-8
226
3.0
M
W
15.4
24'
12.7
1.80(22.81, 2.10 146.6)
60
10,
CALLA- T cell
15
93,XX.+X.+X.+ l.+
1.+2.+2.+3.+3.+4.+4,+5.+5.+8.+8.+8.+8.fB8,+9,+
+10.+11.+11.+12,+12.+13,+13,+14,+14,+15,+15,+16,+16,t17,+17,+18,
16. 19. 19.+20,+20,+21,+2
1. +22. +22.+ 2i17ql(13)/46.XX171
203
13
M
0
15.8
23
1.00 (77.7). 1.91 (10)
7
45
CALLA- T call
352
14
+ 7(10)/46,XY( 11)
+ 7(2)/46,XYll81
92,XY.
8.6
11
F
W
6.2
1.00 (66.2). 1.98 (32.21
92,XY.
+
90
2.5
+
95
22
M
1.93 (58.91
+
CALLA' T cell
+
+
92,XY,+X,+Y,+2.+2.+5.+5.+7,+7,+8.+8.c9.+9,+
lo,+ lo,+ 11,+ 11,+ 12,+12,+ 13.
13.+ 14.+14,+15,+15,+16,+16,+
la,+ 18,+19,+19.+20.+20.+21,+21,+22,
22. 2deN 1l(p321. 2&1(3)(q2 1), 2da(4)t147)(q35:71, Zr(7). Zmw(l3)/
46,XY. -4, -6,deNl )(p321,de1(3)(q211, +der(4)1(4:7)(q35:7) +r(7)(6)/46,XY( 1)
+
XX.del(B)(q15q21I.del(9Np12-p 13111I
9 1,XX. 7(20)/46.XX1201
91.XX+X,+X.+1,+1,+2,+2,+3,+3,+4,+4,+6,+6,+7,+7,+8,+8,+9,+10,+10,+11
+11.+12,+12.+13.+13.+14.114.+16.+16.+18,+16,+17,+17,+18,+18,+19,+19,
+20.+20.+21, +21, +22. +22. +2del(8)~ql5q2l).dell9~1~12pl3)(14)/46.
9 O ~ X X ~ + X ~ + X . + X ~ + 1 ~ + ~ , + 2 , + 3 ~ + 4 ~ + 4 , + 5 , + 5 , + 6 ~ + 6 , + 7 , + 7 ~ + 7 , + 8 , + 8 , +10.
9,+
+lo,+ 11,+12.+ 13,+ 14,+ 14,+ 15.c 16,+ 17,+17,+17,+ 16.f 1 8 . i 19.C 19,+20,
+20. + 2 1.+21.+2 1,+21.+22. + 2 2 , + d e r ~ l ~ t ~ l : 1 3 ~ ~ ~ 3 6 : q l 4 1 ~ 8+21(6)/46,XXl10)
~/47,XX,
2+
94+
31
7
103+
+
CALLA' early prsE
M
21
13+
8
- 17. +der(l7)t(17:7)(q25:7) (9)/46,XY(B)
69.XX. +X. +Y.+7,del111~p13~.~1(6~1q21q2771,
37
M
W
W
9.2
4.6
20
BM
N
EM
1+
88,XX. 7161/46,XX(5)
89,XY. +7(22)/46,XY13)
69,XY. 7(22)/46,XY14)
+
+22(8)/46,XX112)
42
5.6
8.9
+ + +
3+
+
5
6
5
1.00 (59). 1.95 (31.4)
95
early pre-B
CALLAt
19
1.00 (64.3). 1.97 125.4)
75
CALLA- T cell
27
1.96 (66.7)
25.9
11.2
1.00(55.91, 1.92 (31.8)
85
95
14.5
2.00 (82.51
CALLA+ T cell
6.0
12.5
1.00 (44.3).1.92 (40.5)
1.95 (83)
70
95
95
35
5.0
1.92 174)
+
8S,XY,del(6)(ql21. +?I12)/46,XYW
+
24+
31+
20+
30+
I+
1+
(mol
Remission
Duration
12+
+ 7(201/46,XY(20)
+
+
+
+21
Type of
Failure
84,XX.+X.+ 1.+2,+3.+4.+5.+5.+6,+6,+7,+7,+7,+7,+8,+6,+9,+10,+10,+11,+
11,
+12,+ 12,+13,+13,+14,+15.+
16.+ 17.+17,+18.+18.+
19.+ 19,+20,+20,+21,+21.
62,XY.
+
+
+
62.XX.f 1.+2.+4.+4.+5.+5.+5.+6,+7,+7,+
10.+11.+12.+ 12.+ 13.+ 14.+ 14.+ 15. +15.
16,+ 17.+ 18. 18,+ 19,+ 19.+20. +20,+21,+2 1,+22. 22. +2de1~8)lq22),+Zde11911p13).
+der( 1It11:511p 1 3 3 15l,tl1:5)(5: 10Np13:p 15.41 3 ; 1311
~ 15)/ 75,XX. 1, +2. 4. +5. 5, 6. 6,
+7.+10,+11,+12,+12,+13,+14,+
15,+15,+16. +17.+ 18.f 19.+20,+21,+21.+22,
+22. +2de1(611q221, +dsl(9)(p13). +der( 1)t (1:5)(~13.~15).t(1;51~5:
10~(~13:~15q13:~13)
/5)/46,XX(2)
82,XY.+X.+Y.+ 1,+ 1,+2,+3,+4,+5,+6,+6,+7,+8,+8,+10,+
lo,+ 1l.+
1l.+
12,+ 12,
13.+14.
15.f 15.+ 16.+ 16.+ 17.+18.+ la.+ 19.+ 19.+20,+20,+21.+21.+21,
+22,2t(4: 1 1)(q21:q23)( 1 1V46,XYI 1I
+
68.XX.+X,+X.+3,+4,+5,+5,+8,+6,+9.+
lo.+ 11,+ 12,+ 13,+16,+18,+21,+21,+21,
22. inv12)1p36q23),+der( 14)t114:7)lq32:71(18)
73,XX,dup( 1)(q21q441, 7141/46,XXI 1I
+ 18.
+l9,
1 I.+
12,+ 13.+ 14.+15.
12,+ 14.f 14.+ 17.+18. +21,
+21.
203
4.7
3.6
7
9.2
9.3
37
5.9
17
14.3
M
F
W
B
F
W
F
5.3
M
W
16.9
CALLA+
CALLA' pre-E
CALLA' early pre-E
8
256
16
M
15.
CALLA- T cell
190
7
4.6
M
CALLA- T cell
W
7.9
14.
134
W
19.2
13
8
15
9.2
16
F
W
7.1
86
90
CALLA+ pre-8
256
8.8
3.7
M
19.0
85
CALLA- T cell
1.00 1451, 1.82 145.8)
4.5
NO
1.69 (67.2)
NO
95
CALLA+ early pre-8
15.0
10
1.00169.1). 1.75 (26.11
7
38
1.64 132.4). 1.77 (30.81
95
7
CALLA+ p r s 8
NO
2
12
80
NO
1
W
NO
7
CALLA+ eariy pre-8
14,+ 1 7 . 1 18,+20,+21.
68,XY.+X.+Y.+4,+6,+6,+6,+6,+10,+10,+11,+12,+14,+15,+16,+17,+18,+18,
+21.+2 1.+21 .7del~l)(pl1).
+i(7q)(E)/46,XY(12)
10,+10,+11,+
11,+12,+14,+
7.7
+
67.XV,+X,+l,+2.+3.+4,+6,+6,+7,+8,+9,+
+21,+21~12)/46,XY~101
lo.+ 11,+
+ der(9)t(1:8l(q3 l:ql31(9)/46,XY( 11)
68,XX.+X.+1.+2.+3.+3.+4.+6.+8,+6,+6,+7,+9,+ 10.+10.+11.+
19,+21,+22(6)/46,XX(16)
6
5.5
F
11
M
8
6.5
W
4.0
NO
96
CALLA' pre-E
+
66,XY,+X,+4.+5.+6,+7,+8,+8,+
22.de1(9)(qZZI.t(7:1OI(q21:qZ 1),
KawotVpe (no. of metaphases)
9.0
2.9
4.4
% of Leukemic
Cells in S Phase
80
9
1.45 184.51
90
prsE
CALLA'
PrbB
1.46 181.2)
80
CALLA+ eariy pre-E
1.31 (34.21, 1.47 144)
1.46 (81.51
DNA Index
(% of leukemic
cells in Go/G,)
90
CALLA+ early p r s 8
Percent
Blasts
CALLA- early pr-8
16
320
49
98
190
87
233
ImmunophenoNpe
45
9
Platelat
( x 109/L)
7
10
107
M
H
14.8
8
12
W
10.4
F
7
3
F
W
11
F
W
7
10
6.3
6
19
8
M
W
38
15
6
M
M
WEC
Hg
1x 109/L) Iglbl
F
W
W
W
Race Sax
7
Near-tetraploid
4.7
1
Near-triploid
Patient
Table 1. Clinical and Laboratory Findings in Patients With Near-Triploid or Near-Tetraploid ALL
E
--I
m
c
-0
N
(0
593
NEAR-TRIPLOID AND NEAR-TETRAPLOID ALL
Table 2. Morphologic Characteristics of Leukemic Blast Cells in
Patients With Near-Triploid or Near-Tetraploid ALL
Patient
FAB
%
Large
No.
Classification
Blasts.
Near-triploid
1
L2
2
L1
3
L1
4
L1
5
Inadequate
6
L1
33
<5
5
15
?
25
Near-tetraploid
7
L2
8
L1
9
L1
10
L2
11
L1
12
L1
13
L1
14
L1
15
L1
16
L1
17
L2
18
L1
19
L2
20
L1
21
L1
22
L2
23
L2
24
L1
25
L1
26
L1
~~~
18
64
15
60
10
5
45
45
5
10
45
t5
25
35
12
70
70
20
<5
25
Clumped
Chromatin
+
+
-
Cleaved
Nudeus
Vacuolated
Cytoplasm
+t
+
-
+
?
+
+t
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
?
+
-
+
+
+
+t
+
+
+
+
+
+
+
+
+t
+
~
Abbreviation: FAB, French-American-British.
*Size twice that of a small lymphocyte.
tRieder cell formation.
years). They were significantly older than patients with ALL
of all other ploidy groups (median age 4.8 years, P = .Ol),
and 8 of 20 were greater than 10 years at diagnosis. Their
leukocyte counts ranged from 1 to 203 x109/L (median,
8.2 x 109/L); platelet counts from 8 to 352 x109/L (median, 44 x 109/L); and hemoglobin levels from 2 to 15 g/dL
(median, 8 g/dL). None of these values differed significantly
from those of other patients (data not shown). A mediastinal
mass was present in four cases (nos. 18,21,22, and 26), and
initial CNS leukemia in patients 7 and 26. Of the 19 cases
with complete blast cell immunophenotyping, 9 were classified as T-cell (CDl-/CD3-, CDl+/CD3-, and CD3+ in 3
cases each); 5 as pre-B; and 5 as early pre-B-ALL. This
frequency of T-cell ALL was significantly higher than that
found in the patients with other ploidies (47% v 14%,
P < .001). Five cases (nos. 10, 12, 14, 15, and 24) were not
tested for myeloid-associated antigen expression. Of the 15
cases tested, 6 expressed one or two myeloid-associated
markers:case8, CD15;case 11,CD33;case 16,CD13/CD15;
case 19, CD13/CD33; case 22, CD15; and case 23, CD33.
Six patients have relapsed or died; five of these had T-cell
ALL. Most of the patients who remain in remission have
been followed for less than 2 years.
DISCUSSION
The 1.0% frequency of near-tetraploidy in this series
substantiates the rarity of this chromosomal abnormality in
childhood ALL. Even fewer cases would have been detected
had karyotypic analysis been used alone. The Third International Workshop on Chromosomes in Leukemia reported
only one near-tetraploid case among 330 banded cases of
childhood and adult ALL.27 Heerema et all3 found one
near-tetraploid case in their study of 70 newly diagnosed
children with ALL. In our earlier study of 519 newly
diagnosed childhood ALL cases with banded leukemia cell
chromosomes, four cases (0.8%) were near-tetraploid.'
Near-tetraploid cases in this study were significantly more
likely to have a T-cell immunophenotype (47%), and L2
morphology (30%), and to be older at diagnosis (median age,
8.6 years) than the cases with other ploidies. Similarly, of the
six cases of near-tetraploid childhood leukemia previously
reported by other investigators, the median age at diagnosis
was 11 years, three cases had T-cell ALL, and three had L2
morphol~gy.'~'~*'~
Despite contemporary intensive therapy, 6
of our 20 patients have relapsed or died, further, the
follow-up for most of the patients who remain in remission is
short. These differences are particularly striking in comparison with cases of hyperdiploidy >SO, which account for
approximately one fourth of children with newly diagnosed
ALL. The median age of these cases at diagnosis is 3.6 years,
only 3% have a T-cell immunophenotype, and 10% have L2
morphology.' More importantly, hyperdiploid >SO cases
have a favorable prognosis: at least two thirds will become
long-term survivors with contemporary treatment.8*2'*29
Thus,
near-tetraploid ALL should be regarded as a distinct entity
from other hyperdiploid >SO cases.
Near-tetraploid cases appeared to have a high frequency
of myeloid-associated antigen expression. Six of the 15 cases
tested expressed one or more of three myeloid-associated
antigens CD13, CDl5, and CD33. In our earlier study of 372
childhood ALL cases with a comprehensive panel of myeloidassociated MoAbs representing seven cluster groups, 6 1
cases ( 16.4%) expressed myeloid-associated antigen(s) and
31 (8.3%) expressed CD13, CD15, or CD33." In that study,
myeloid-associated antigen expression had no effect on treatment outcome in the context of intensive chemotherapy. Of
the six near-tetraploid cases described here with myeloidassociated antigen expression, one did not achieve remission
and one has relapsed, with relatively short follow-up. Additional studies are needed to determine the prognosis of this
subgroup of patients.
Near-triploidy is an even rarer finding in childhood ALL.
We are aware of only one reported case in a child; this patient
had the Philadelphia chromosome and a T-cell phen~type.'~
In the present study, only 6 of 1,971 children (0.3%) with
newly diagnosed ALL had a near-triploid leukemic cell line.
The initial clinical features of these patients did not appear to
differ substantially from those of reported hyperdiploid >SO
cases,' and all six patients remain in continuous complete
remission. However, 3 of the 6 near-triploid cases had a
pre-B immunophenotype, which was observed in only 16%of
PUI ET
594
AL
F b 1. Bonbmarroww.r
fromuuSrhoWingL1 lymphoM.nr wtth clumpd chromatin
and cloavod nuclei.
Fig 2.
Bono marrow a " r
from a s o 23 rhowfno I2lpphobhm with dumpd chronutinond duwd nud.i.
595
NEAR-TRIPLOID AND NEAR-TETRAPLOID ALL
our previously reported hyperdiploid >50 ALL cases.' Further, only 13 of 70 children with pre-B-ALL had blast cell
hyperdiploidy >50.2'Thus, the clinical and biologic relationship of near-triploid cases to other hyperdiploid >50 cases
remains unclear.
Large blast cells have been described in five cases of
near-tetraploid l e ~ k e m i a . ' ~ .In
~ 'our
. ~ ~study, the presence of
large blast cells or large nuclei was not a prominent feature of
near-tetraploid cases; only 4 of the 20 patients had greater
than 50% large blasts detected in bone marrow smears. This
is not surprising because the volume of a nucleus can be
doubled by a 1.26-fold increase in diameter, a difference that
may not be appreciable visually. Moreover, the size of nuclei
depends on many factors in addition to the DNA content. For
example, the diploid nuclei are larger in myeloblasts than in
lymphoblasts, and L2 lymphoblasts are larger than L1 blasts.
Indeed, of the five previously reported near-tetraploid cases
with large blast cells, four had acute nonlymphoblastic
leukemia and the fifth had L2 ALL.'293'q32
Characteristic
features in our near-triploid and near-tetraploid cases (clumping of the chromatin with cleaving of the nucleus) may
represent an attempt of lymphoblasts to accommodate the
extra DNA.
Endoreduplication of a cell in the diploid range, with or
without subsequent gain or loss of chromosomes, appears to
be the most feasible mechanism to account for neartetraploidy, although fusion of two different diploid cells has
also been ~uggested.~'
The most compelling evidence for the
former explanation is the presence of paired chromosomes
containing the same rearrangements or deletions in 6 of our 9
near-tetraploid cases with structural abnormalities. Detailed
analyses were unsuccessful in the remaining cases because
chromosomes were fuzzy and insufficiently spread, a problem
also encountered by other investigator^.^^.'^ Several mechanisms have been proposed for the development of neartriploidy, including nondisjunction, duplication of hypodiploid cells, loss of chromosomes from tetraploid cells, and
multipolar mitosis of tetraploid cells.I4 The absence of a
hypodiploid line or paired marker chromosomes in our cases
suggests that nondisjunction is the most likely cause.
Results of flow cytometric determination of cellular DNA
content and conventional cytogenetic analysis of ploidy were
closely correlated in this study. DNA content can be determined by flow cytometry for virtually all cases because the
measurements are not affected by the mitotic index of the cell
population. However, flow cytometry does not identify the
specific chromosomal changes, which may have important
prognostic and biologic implications. Thus, the two tests
should be used in tandem in studying patients with leukemia.
Cases identified as having near-tetraploid stem lines by
either method should be categorized separately from the
prognostically favorable hyperdiploid >50 group. Whether
near-triploid cases are clinically and prognostically distinct
from those with hyperdiploidy >50 requires further study.
ACKNOWLEDGMENT
We thank C. Wright for editorial review and P. Vandiveer for
typing the manuscript.
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