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Mutation Research, 247 (1991) 231-240 © 1991 ElsevierSciencePublishers B.V. 0027-5107/91/$03.50 ADONIS 002751079100083E

MUT 00057

Chromosome abnormalities in human cancer and leukemia Avery A. Sandberg Southwest Biomedical Research Institute, Scottsdale, A Z 85251 (U.S.A.)

Keywords: Chromosomeaberration; Cancer; Leukemia

Summary The meaning and application of chromosomal (cytogenetic, karyotypic) changes in human leukemia and cancer have been succinctly reviewed in this article. Thus, the usefulness of these changes in the diagnosis, classification and prognosis of various leukemic conditions and, more recently, of solid tumors is stressed and their application to molecular studies indicated. The meaning of primary (specific) and additional (secondary) karyotypic changes in malignant and benign tumors is discussed. Tables containing the common cytogenetic changes in leukemias and tumors, including benign ones, are included.

The human genome, made up of the 46 normal chromosomes, usually does not tolerate any changes without the appearance of phenotypic and other abnormal manifestations at a general or specific cellular level. The very large number of congenital translocations, deletions, insertions and inversions, and loss or gain of whole chromosomes, are characterized by these cytogenetic anomalies affecting all the cells of the body. However, when only specific cells are affected by appropriate chromosome changes, these may be associated with, or lead to, malignant transformation of such cells. Though it is possible that some neoplastic conditions may be associated with submicroscopic rather than visible primary chromosomal changes not evident even with optimal cytogenetic approaches presently in use, the number of such conditions is probably relatively small. Thus, the bulk of human leukemias and cancers is

Correspondence: Avery A. Sandberg, M.D., Southwest Biomedical Research Institute, 6401 East Thomas Road, Scottsdale, AZ 85251 (U.S.A.).

accompanied by cytogenetic changes (Sandberg, 1990). Chromosome changes in human cancer and leukemia are almost always confined to the affected cells and are not present in the other somatic ceils of the body, e.g., blood lymphocytes and skin fibroblasts. This means that in the case of a tumor, parts of it must be examined cytogenetically in order to ascertain the karyotypic (chromosomal, cytogenetic) changes which may be present. In the case of leukemia, as often as not, it is marrow cells that have to be analyzed, though when necessary circulating blood cells can be examined. However, cytogenetic information thus obtained from blood cells, with very rare exceptions, is not as consistent or optimal as that based on results established in marrow material. A high rate of success in the cytogenetic analysis of leukemic and cancerous cells requires that viable cells or tissue be sent to the laboratory, that this material be processed as expeditiously as possible (e.g., this is particularly true of cells from cases of acute lymphoblastic leukemia), that the tumor material not be contaminated with bacteria

232

or other organisms, and that the material or cells not be fixed. The latter can best be avoided by engaging the full cooperation of the pathologist, who is a key figure in the study of solid tumors, in particular. Thus, in order to obtain comprehensive cytogenetic results in human neoplasia and their meaningful interpretation, the interaction of the clinician, surgeon and pathologist with the cytogeneticist is an essential element. Based on the cytogenetic experience in human cancer and leukemia gained in the decade and a half following the establishment in 1956 of the correct number of chromosomes in human cells and, particularly, on the experience in the decade and a half subsequent to the introduction of banding techniques in 1970, it became apparent that the information gathered could be applied usefully and reliably in the following aspects of cancer and leukemia: (1) diagnosis; (2) classification (including nosology); (3) prognosis; and (4) molecular studies. In the following, examples for each of the areas listed will be given.

Primary (specific) or recurrent changes in cancer and leukemia

chromosome

It is now well established that leukemias, particularly of the acute type, are often characterized by primary (specific) or recurrent chromosomal events that not only are, in all probability, related to the genesis of the disease, but also point to subsets or subtypes in what has been thought to be well-defined entities (Sandberg, 1986). For example, the French-American-British (FAB) classification of the acute leukemias, both for the acute non-lymphocytic (ANLL) and lymphoblastic (ALL) types, has defined entities as based on morphologic, cytochemical and immunologic criteria. Yet, cytogenetically it has been shown that each such entity probably consists of a number of subsets (Tables 1 and 2); each subset is not only characterized by a specific karyotypic change but often also by a median survival, and by cytologic and clinical manifestations peculiar to each subentity. A good example is the M2 type of acute myeloblastic leukemia (AML). At least 3 cyto-

TABLE 1 COMMON A N D / O R SPECIFIC C H R O M O S O M E C H A N G E S IN ACUTE N O N - L Y M P H O C Y T I C L E U K E M I A (ANLL) M1

M2

M3

M4

- 7 +8 del(5c0 - 5 t(9;22)(Ph + )

t(8;21)(q23;q12) -7 +8 del(5q) +4 t(6;9)(p23;q34)

t(15;17) i(17q)

inv/del, t(16) +8 -7 +4 t(10;ll)(p14;q13-14) d e l ( l l ) / t ( l l q 1 3 - 1 4 ) or (11q23)

M5

M6

M7

del,t( 11 q)(ql 3 - 14) +8 t(6;11)(q27;q23) t(9;ll)(p21;22;q23) t(8;16)(pll;pl3) t(10;ll)(p14;q13-14)

-7 +8 del(5q) del(20q)

+21 t(1;3)(p36;q21) a ins(3; 3)(q26 ;q21 q26) ~ inv(3)(p21q26) a

Secondary leukemia

del(5q) -5 del(7q) -7 t(1;7)(pll;pll) +4 a

These changes may be seen in other types of ANLL (e.g., M1 and M2) megakaryocytes a n d / o r platelets.

and are

often associated with abnormalities of the

233

genetically well-defined subentities have been described in this group, i.e., AML with t(8;21), another with t(6;9) and still another with +4. Furthermore, A M L with t(8;21) tends to have a relatively good prognosis as opposed to the very poor prognosis seen in AML with other karyotypic changes. To a lesser degree, what has been said of the M2-type AML is also true for all other types of acute leukemia. Although cytogenetic data in acute leukemia have been used to a limited extent by oncologists caring for patients with these diseases, more widespread use of such data and ultimately the tailoring of therapy to each subset of acute leukemia are developments for the future. Thus, in evaluating survival and other clinical data on acute leukemia en masse on the basis of the FAB classification, one loses sight of the heterogeneity of the entities being considered. There is little doubt that in the future each cytogeneticaUy defined acute leukemic subset or subtype will have to be approached in its own right and treated as a separate entity. The presence of the primary (specific) chromosome change as the sole cytogenetic abnormality in the affected cells, as mentioned above, is much more commonly encountered at diagnosis in

leukemia than in solid tumors. This is possible due to the fact that the clinical (and hence biologic) manifestations of leukemia generally become apparent at a much earlier stage of the disease than do those of solid tumors, and therefore, the neoplastic (leukemic) cells are examined at a time when they contain only the primary karyotypic change. Solid tumors usually contain a host of karyotypic changes making it very difficult to establish the primary (specific) cytogenetic event, in contrast to the leukemias where often only one event is present (Sandberg, 1987; Sandberg et al., 1988). This masking of the primary karyotypic change in solid tumors continues to be a major obstacle in asserting such an event in a significant percentage of solid tumors. However, with time and the study of a large number of tumors of a particular organ, sooner or later tumors are encountered in which a single karyotypic event is present, thus constituting the primary cytogenetic change (Table 3). This appears to be particularly true of epithelial tumors; sarcomas often have a single or a few karyotypic events, thus facilitating the establishment of the primary chromosomal changes in such tumors. A significant percentage of solid tumors have a

TABLE 2 COMMON AND/OR SPECIFIC CHROMOSOME CHANGES IN ACUTE LYMPHOBLASTIC LEUKEMIA (ALL) FAB types L1 and L2

t(l:ll)(p32;q23) t(1;19)(p23;p13) t(Y:llXq21;q23) del(6q) del/t(9p) t(10;14)(q24;qll) t(ll;14)(pl3;qll) del/t(12p) t(9;22)(q34;qll)

near-haploid pre-B ALL pre-B-ALL Early B-precursor ALL, mixed phenotype Common ALL T-ALL or early precursor ALL T-ALL T-ALL Common ALL Early B-precursor common pre-B ALL

F A B type L3

t(2;8)(p12;q24) t(8;14)(q24;q32) t(8;22)(q24;qll) T-cell A L L

t(8;14)(q24;q11) del/t(9p) t(10;14)(q24;qll) t(1;14)(p23;q11)

B-ALL B-ALL B-ALL

(L1) (L1) (L1 and L2) (L1 and L2) (L1 and L2) (L1 and L2) (L1 and L2) (L1 and L2) (L1 and L2)

234

very low mitotic index, necessitating culture of the cells, which may not be successful in all cases or may lead to overgrowth by normal (diploid) cells. The morphology of the chromosomes in solid tumors is more often fuzzy and less than optimal for detailed analysis than that encountered in leukemias. This aspect of solid tumors, however, has largely been overcome by recently introduced innovations in methodologies (Gibas et al., 1984; Trent et al., 1986; Limon et al., 1986). These innovations include a number of steps established in our laboratory, the most crucial of which consists of: exposure of the cells to collagenase throughout the incubation or culture period, the use of a modified hypotonic solution for the swelling of cells, the use of methotrexate for clearer

banding of chromosomes and, most importantly, frequent examination under the microscope of the incubated or cultured cells for their mitotic activity in order to establish the peak of such activity (Gibas et al., 1984; Trent et al., 1986; Limon et al., 1986). Solid tumors are not infrequently infected (particularly those of the gastrointestinal tract, lung and cervix), so that upon culture, even for a brief period of time, the infecting organisms destroy the tumor material or make cytogenetic examination impossible. In addition, for optimal chromosome results, viable tumor tissue is necessary; however, some tumors are necrotic and may not yield sufficient metaphases for analysis. The high success rate of cytogenetic analysis

TABLE 3 SPECIFIC (PRIMARY) CHROMOSOME CHANGES IN TUMORS Tumors

Chromosome

Benign Meningioma Mixed tumors of salivary glands Lipoma Colonic adenomas Leiomyoma

- 22.22q t(3;8)(p21 ;q12),t(9;12)(pl 3; - 22q13-15) t with 12q14 12q - , + 8 t(12;14)(q14-15;q22;24)

A denocarcinomas

Bladder Prostate Lungs (SCLS) Colon Kidney Uterus Ovary

i(5p), + 7, - 9/9q,1 lp del(10)(q24) del(3)(p14p23) 1 2 q - a,+7 a , + 8 , + 1 2 a,17(qll) a del(3)(pll-p21) lq- a 6 q - a,t(6;14)(q21;24) a

Sarcomas

Liposarcoma (myxoid) Synovial sarcoma Rhabdomyosarcoma (alveolar) Extraskeletal myxoid chondrosarcoma

t(12;16)(q13;pll) t(X;18)(pll.2;qll.2) t(1 ;13)(q37;q14) t(9;22)(q31,q12.2)

Embryonal and other

Testicular (germ cell tumors) Retinoblastoma Wilm's tumor Neuroblastoma Malignant melanoma Mesothelioma Ewing sarcoma and peripheral neuroepithelioma Not yet proved to be primary. b Associated with a consitutional chromosome change. a

i(12p) del(13)(q14) b del(ll)(plS) b del(1)(p32p36) del(6)(pllq27) ",i(6p) a,del(1) (pllq22) a,t(1;19)(ql2;qlS) del(3)(p12-p23) t(ll;22)(q24;q12)

235

m

. / _ ~ _

p11.2 -

pll

-

-

-q11.2

-

q13

-

-

iiii;ii

16

der (12)

der (16)

der(18)

18

Fig. 1. Schematic presentation of the specific karyotypic change characterizing synovial sarcoma, i.e., t(X;18)(pll.2;qll.2) (Turc-earel et al., 1987). This change has been used diagnosticaUy to differentiate this tumor from others with which it may be confused. Little is known about the genes involved in this translocation.

Fig. 2. Primary chromosome changes seen in synovial liposarcoma, t(12;16)(q13;p11). This change has been of help in differentiating other myxoid tumors with which the liposarcoma type may be confused. Though a similar translocation may be seen in the benign counterpart of liposarcoma, i.e., lipoma, it usually involves chromosomes other than chromosome 16 and molecularly breaks on chromosome 12 appear to be different in lipoma vs. liposarcoma.

obtained with sarcomas may be related to the fact that carcinomas have more complex karyotypes (possibly related to a later stage of the tumor at diagnosis vs. that of sarcomas), the higher mitotic

index in sarcomas and the relative ease with which sarcomas can be cultured in vitro for short or long periods. The list of solid tumors characterized by a

X

der(X)

A

B ~z

112

It.t

13 tL%\\\\\~3 t2 =

tl2

~2 2t 22

q14-15 "-P

2~ 2t

.e-q23-ql

Zt 2~ Z41 24 2 24 3

12

14

der12

derl4

Fig. 3. Partial karyotype and schematic presentation of the translocation (12;14)(q14-15;q23-24) seen in a significant number of leiomyomas, benign tumors of the uterus.

236 primary or recurrent karyotypic change is already impressive (Table 3) and is continuing to grow with new entities being published at an increasing rate. Thus, in time the bulk of solid tumors, both malignant and benign, will be shown to be associated with primary or recurrent chromosome changes unique to each tumor type and subtype. Examples of karyotypic changes which have diagnostic implications are given in Figs. 1-3. In Fig. 2 is shown a characteristic chromosome change t(12;16)(q13;p11), seen in myxoid liposarcoma (Limon et al., 1986; Turc-Carel et al., 1986). In fact, this change can be (and has been) utilized by pathologists in differentiating myxoid tumors which can be confused with myxoid liposarcoma. It is possible that the key chromosomal event in myxoid liposarcoma is the break (shown as occurring at 12q13) on chromosome 12.

Significance of chromosome changes in benign tumors Our knowledge of the chromosome constitution of benign tumors is rather limited when compared with that of malignant tumors, a very low mitotic rate being the main limiting factor (Sandberg, 1990). It has been generally accepted that benign tumors have a normal (diploid) karyotype. However, the abnormal cytogenetic findings in tumors considered benign on histologic and behavioral grounds present a serious dilemma to cancer cytogeneticists with regard to the role of chromosome anomalies in malignant neoplasms. Thus, cytogeneticists are faced with the fundamental question as to whether the generally accepted view that chromosomal anomalies indicate a malignant state is wrong and whether all benign tumors with chromosome anomalies should be considered premalignant, if not already involved in malignant transformation. Colon adenomas, meningiomas, mixed salivary gland tumors, lipomas and leiomyomas, all benign entities in which consistent chromosome changes have been found, may serve as good examples for discussion (Sandberg, 1990). The establishment of specific changes in benign tumors, e.g., - 2 2 in meningioma, translocations involving chromosome 12 in lipoma and leiomyoma, and t(3;8) in salivary gland tumors, allows a

reliable differentiation of benign tumors from their malignant counterparts in complicated cases (Sandberg, 1990). The presence of only normal (diploid) metaphases in a tumor, especially on repeated examinations of various parts of the tumor, speaks strongly for a benign rather than a malignant tumor. However, this is an area in which molecular approaches may ultimately turn out to be the most reliable. The demonstration (Limon et al., 1986; TurcCarel, 1986) of a specific chromosomal change in myxoid liposarcoma t(12;16)(q13;qll), led us to examine benign lipomas (Turc-Carel et al., 1986). The latter almost never became malignant and, hence, the findings in about 50% of the lipomas examined indicate that they are associated with a recurrent translocation involving chromosome 12 at band q14, the other participating chromosome being variable in nature (e.g., to date chromosomes 2, 3 and 14). This has afforded the cytogeneticist and pathologist a means of differentiating confusing liposarcoma from benign lipomas. The same can be said for leiomyomas and uterine leiomyosarcomas in which the rather specific change affecting the former, t(12;14)(q1415;q22-24), easily differentiated the benign leiomyoma 'from the leiomyosarcoma (Sandberg, 1990). However, in other situations, e.g., colonic adenomas and probably in salivary gland tumors, the changes seen in the benign lesions may carry over or overlap with those in adenocarcinoma of these organs and hence, not be useful diagnostically as are the changes in lipoma and leiomyosarcoma (Sandberg, 1990). In my opinion, the cytogenetic findings in benign tumors hold much promise in being useful as a diagnostic parameter in differentiating them for their malignant counterparts. When faced with the presence of only cytogenetically normal (diploid) cells in a tumor, it cannot be assumed that these cells are necessarily of tumor origin, since it is not unusual to encounter diploid cells in most frank cancers. If in fact, in some tumors, the preparations for chromosome analyses yield only diploid cells. The presence of cytogenetically normal cells in tumors is not unexpected since frequently stromal and supporting elements in carcinomas and sarcomas appear to be of normal tissue origin and, thus, may be responsi-

237

ble for the cytogenetically normal cells present in tumors. Another possibility is infiltration of the tumors by normal leukocytic elements, not a rare finding in some cancers and which may be reflected in the finding of chromosomally normal cells in the preparations. Although it may be contended that such cytogenetically normal cells are neoplastic, it is my view that if they are, the changes are submicroscopic and, hence, take place at a molecular level beyond the resolution of cytogenetic techniques presently used. Thus, the presence of only diploid cells cannot be used as a diagnostic criterion in differentiating benign from malignant tumors. Cytogenetic studies on benign tumors have raised a number of cogent and perplexing questions. Not only have certain benign tumors (meningioma, lipoma, leiomyoma, salivary gland adenomas) or a group within such tumor entities been shown to be characterized by specific chromosome changes, but also some of them have been demonstrated to be associated with very complex karyotypes. Were not the benignity of these tumors an established fact, the complex cytogenetic findings might spuriously lead one to believe that they are indicative of malignancy. The karyotypic findings in benign tumors may indicate that they involve genes which are related to cellular proliferation but not to malignant transformation. This appears to be true regardless of the complexity of the karyotypic changes. Further studies, including molecular, are not only badly needed, but will also shed considerable light on those genes which are necessary for tumoral proliferation but lack the ability to transform the cells. Undoubtedly, the information gained with benign tumors will be of crucial value in our understanding of cellular events, chromosomal and subchromosomal, involved in neoplasia. An example of the application of cytogenetic results in the Classification or nosology of tumors is that supplied by Ewing sarcoma. This tumor was shown to have a specific chromosomal change consisting of a translocation (ll;22)(q24;q12) (Turc-Carel et al., 1984). This change was subsequently shown to be present in a number of other neuroectodermal tumors, but not in neuroblastoma. In the past Ewing sarcoma was thought

to be related to neuroblastoma and, in fact, the disease was treated similarly. The cytogenetic data indicate that the tumors are probably not related and that Ewing sarcoma belongs more properly with other types of tumors of neuroectodermal background. Chromosomes and molecular studies

With the rapid advances in molecular biology as applied to cancer genetics, it may be possible in the future to recognize genetic defects or alterations in chromosomes in most states and those which are not detectable with presently available cytogenetic techniques. Such defects may be directly related to the genesis of or predisposition to specific types of leukemia or cancer, in which case examination of non-involved cells with appropriate molecular techniques will prove to be of value as a predictive if not diagnostic parameter. The outstanding example of the application of cytogenetic findings to the deciphering of molecular events in a malignant state is the story of the Philadelphia (Ph) chromosome (Figs. 4-6). The establishment of the exact breakpoints on chromosomes 9 and 22 involved in the Ph translocation in chronic myelocytic leukemia (CML) and, by extrapolation, the possible genes located in these chromosome areas, the oncogene c-abl on chromosome 9 and the gene bcr on chromosome 22, made it possible to demonstrate the events associated with the genesis of the Ph and their consequences (Sandberg, 1990). It was shown that as a result of the translocation, part of the oncogene c-abl is translocated to the abbreviated chromosome 22 in which a break within a 5.2-kb region known as bcr had occurred. The juxtaposition of part of c-abl to the remaining bcr segment results in a new and abnormal gene whose products are abnormal and may possibly be directly responsible for the CML. A similar application of the cytogenetic findings for molecular approaches has been accomplished in lymphomas, particularly of the Burkitt type (Sandberg, 1990). Thus, the translocations t(8;14), t(2;8) and t(8;22) have been shown in each case to involve the oncogene c-myc located on chromosome 8 and various immunoglobulin genes located on the other chromosomes taking part in

238

6

7

8

4

5

11

12

H 13

14

IJ

15

16

~!

19

61o

20

21

|t 17

18

l,- " 8 22

Y

Fig. 4. G-Banded karyotype of a marrow cell from a patient with chronic myelocytic leukemia (CML) showing a Ph chromosome due to a translocation (9;22)(q34;qll) (arrows) as the only karyotypic anomaly. A similar Ph is also seen in some cases of acute lymphoblastic or myeloblastic leukemia.

the translocations. Again, the juxtaposition of an oncogene (c-myc) to genes responsible for immunoglobulin production leads to a situation in NORMAL CHROMOSOMES 9

22

PHILADELPHIA TRANSLOCATION t (9;22)

---q34.1

1 Fig. 5. Schematic presentation of the Ph translocation shown in Fig. 1 showing the breakpoints on chromosomes 9 and 22 and the 2 oncogenes (c-abl and c-sis) affected by the translocation, though only c-abl is directly involved by the break on chromosome 9, whereas c-sis is translocated in toto as a result of the exchange between the two chromosomes.

which transformation of lymphoid cells occurs. The same scenario appears to exist for chromosomal changes involving breakpoints affecting the various genes of the T-cell receptors and bcr genes related to lymphoma. Disappointingly, only a few of the translocations and other structural cytogenetic changes in human cancer and leukemia have been deciphered molecularly. This is primarily due to our ignorance regarding the appropriate genes involved by these changes or the unavailability of proper probes for the performance of such studies.

Additional (secondary) chromosome changes in tumors

It would appear that a tumor (or leukemia) may be at its lowest level of malignancy when only the primary karyotypic change is present and that the appearance of additional chromosome changes may not only be associated with biologic

239 Chromosome

9

C h r o m o s o m e 22

P h i l a d e l p h i a (Ph) Chromosome i

I

5I

5'

c-abl

c_._zr b

3'

3'

I

mRNA 6-7kb mRNA 4.5&6.7 kb mRNA 8-9kb Protein 145kd Protein 160kd Protein 210kd Fig. 6. Schematic presentation of the molecular events associated with the genesis of the Ph chromosome. Shown. in the left and middle schemas are the messenger RNAs (mRNA) and their protein products of the normal c-abl oncogene and bcr gene on chromosome 9 and 22, respectively. In the schema on the right is shown the situation resulting from the Ph translocation in which part of the c-abl oncogene is now juxtaposed to an abbreviated bcr gene at this 3' side. The new and abnormal gene (bcr/c-abl) resulting from the Ph translocation generates an abnormal mRNA and, hence, an abnormal protein product (210 kd) which has been implicated in the possible causation of CML. In Ph-positive acute leukemias the breakpoint on chromosome 22 often occurs proximal to bcr in a significant number of cases leading to an abnormal mRNA and protein product different from those shown in the figure but still abnormal in character.

progression of the tumor but possibly be the direct cause of this progression. As in the leukemias, some studies already indicate that the severity of cancer, as based on such parameters as invasion (stage), pathology (grade), metastasis, and response to therapy, may be related to the number of chromosome changes present. Because the additional cytogenetic changes in solid tumors at diagnosis are often complex and numerous, as differentiated from leukemias in which the finding of only the primary chromosome change is common, they not only tend to obscure the primary karyotypic event, as mentioned above, but also may be indicative of a more advanced stage at which tumors are diagnosed and, hence, are examined cytogenetically. In addition, these additional and diverse changes are probably associated with a host of gene activations and expression (including those of oncogenes) whose order and nature must affect the cancer. The unraveling of the molecular events associated with the additional changes, in addition to those resulting from the primary chromosome change, represents a key challenge in oncology, because the events

will undoubtedly have a crucial relationship to the development of therapy tailored to those events and to the biology of each tumor. Although the additional chromosome changes do not often appear to have a non-random pattern that warrants special attention, examples do exist where they show non-randomness, akin to that in some leukemias. To me it appears certain, that although establishing the primary karyotypic event in tumor subtypes is of crucial importance in pointing to a possible molecular event associated with or responsible for the malignant transformation, the additional chromosome changes in tumors will have to be given special attention since they may be ultimately responsible for the dire consequences of a tumor (metastasis, invasion, recurrence and lack of response to therapy).

References Gibas, L.M., Z. Gibas and A.A. Sandberg (1984) Technical aspects of cytogenetic analysis of human solid tumors, Karyogram, 10, 25-27. Limon, J., P. Dal Cin and A.A. Sandberg (1986a) Application of long-term collagenase disaggregation for the cytogenetic analysis of human solid tumors, Cancer Genet. Cytogenet., 23, 305-312. Limon J., C. Turc-Carel, P. Dal Cin, U. Rao and A.A. Sandberg (1986b) Recurrent chromosome translocations in liposarcoma, Cancer Genet. Cytogenet., 22, 93-94. Sandberg, A.A. (1986) The chromosomes in human leukemia, Semin. Hematol., 23, 201-217. Sandberg, A.A. (1990) The Chromosomes in Human Cancer and Leukemia, 2nd edn., Elsevier, New York. Sandberg, A.A., and C. Turc-Carel (1987) The cytogenetics of solid tumors: Relation to diagnosis, classification and pathology, Cancer, 59, 387-395. Sandberg, A.A., C. Turc-Carel and R.M. Gemmill (1988) Chromosomes in solid tumors and beyond, Cancer Res., 48, 1049. Trent, J., K. Crickard, Z. Gibas, A. Goodacre, S. Pathak, A.A. Sandberg, F. Thompson, J. Whang-Peng and S. Wolman (1986) Methodologic advances in the cytogenetic analysis of human solid tumors, Cancer Genet. Cytogenet., 19, 57-66. Turc-Carel, C., I. Philip, M.-P. Berger, T. Phillip and G.M. Lenoir (1984) Chromosome study of Ewing's sarcoma (ES) cell lines, Consistency of a reciprocal translocation t(11;22) (q24;q12), Cancer Genet. Cytogenet., 12, 1-19. Turc-Carel, C., P. Dal Cin, U. Rao, C. Karakousis and A.A. Sandberg (1986a) Cytogenetic studies of adipose tumors, I. A benign lipoma with reciprocal translocation t(3;12) (q28;q14), Cancer Genet. Cytogenet., 23, 283-290.

240 Turc-Carel, C., J. Limon, P. Dal Cin, U. Rao, C. Karakousis and A.A. Sandberg (1986b) Cytogenetic studies of adipose tissue tumors, I1. Recurrent reciprocal translocation t(12;16) (ql3;pll) in myxoid liposarcomas, Cancer Genet. Cytogenet., 23, 291-300. Turc-Carel, C., P. Dal Cin, J. Lomon, U. Rao, F.P. Li, J.M.R.

Zimmerman, D.M. Parry, J.M. Cowan and A.A. Sandberg (1987) Involvement of X chromosome in primary cytogenetic change in human neoplasia: Non-random translocation in synovial sarcoma, Proc. Natl. Acad. Sci. (U.S.A.), 84, 1981 1985.