Clustering of aberrations to specific chromosomes in human neoplasms. II. A survey of 287 neoplasms

The genomic and spatial mobility of extrachromosomal DNA and its implications for cancer therapy

Extrachromosomal DNA (ecDNA) amplification has been observed in at least 30 different cancer types and is associated with worse patient outcomes. This has been linked to increased oncogene dosage because both oncogenes and associated enhancers can occupy ecDNA. New data challenge the view that only oncogene dosage is affected by ecDNA, and raises the possibility that ecDNA could disrupt genome-wide gene expression. Recent investigations suggest that ecDNA localizes to specialized nuclear bodies (hubs) in which they can act in trans as ectopic enhancers for genes on other ecDNA or chromosomes. Moreover, ecDNA can reintegrate into the genome, possibly further disrupting the gene regulatory landscape in tumor cells. In this Perspective, we discuss the emerging properties of ecDNA and highlight promising avenues to exploit this new knowledge for the development of ecDNA-directed therapies for cancer.

Clinical significance of cytogenetic findings in solid tumors

Chromosome analysis of solid tumors is becoming an increasingly useful tool to help establish a correct diagnosis and to provide prognostically important information. Characteristic karyotypic patterns in terms of degree of cytogenetic complexity and type of nonrandom abnormalities may help to distinguish neoplasia from a nonneoplastic lesion and to differentiate between a benign and a malignant tumor. More importantly, the presence of a specific or pathognomonic change may confirm or refute a suspected diagnosis, provide an alternative, unsuspected diagnosis, and trace the origin of a metastasis. Presently, specific cytogenetic abnormalities may be of substantial, and sometimes decisive, help in four groups of differential diagnostic dilemmas: (1) Benign vs. malignant epithelial tumors of the kidney, thyroid gland, salivary glands, and ovary; (2) Benign vs. malignant mesenchymal tumors of adipose and muscle tissue; (3) Differentiation between various malignant bone and soft tissue tumors: and (4) Diagnosis of undifferentiated small-cell round-cell tumors. In addition to the diagnostic value, karyotypic findings may provide prognostic information. Thus, the presence of an abnormal clone and/or complex rearrangements is a poor prognostic sign in, e.g., carcinomas of the ovary, prostate, bladder, colon, and pancreas. Furthermore, characteristic cytogenetic aberrations are now known to be valuable prognostic parameters in malignant melanoma, malignant fibrous histiocytoma, germ cell tumors, neuroblastoma, and squamous cell carcinoma of the head and neck region. Many of the correlation analyses are preliminary, but they all point in the same direction, namely that cytogenetic studies will soon play the same essential role in the management of patients with solid tumors as they do today in hematologic oncology.

Chromosomal analysis of colonic adenomatous polyps

Chromosomal analysis of 25 colonic adenomatous polyps was performed by a direct method similar to that used in prenatal diagnosis of chromosomal aberration on chorionic villi. Fourteen lesions showed an abnormal karyotype. Two changes were recurrent: trisomy 7 (observed in eight cases) and trisomy 13 (observed in seven cases). No monosomy of the short arm of chromosome 17 was observed even at the level of two polyps with in situ carcinoma lesions.

Complex translocation involving chromosomes #1, #9, and #22 in a patient with chronic myelogenous leukemia

A case of Philadelphia chromosome positive chronic myelogenous leukemia with a complex translocation involving chromosomes #1, #9, and #22 is described. All cells in the bone marrow showed this rearrangement, and Q-banding analysis showed the predominant karyotype to be 46,XY, t(1;9;22)(p22;q34;q11).

Prediction of tumor doubling time in recurrent meningiomas. Cell kinetics studies with bromodeoxyuridine labeling

Eight patients with recurrent meningiomas (four malignant, two hemangiopericytic, and two nonmalignant) were given intravenous bromodeoxyuridine (BUdR), 200 mg/sq m, at the time of surgery to label cells in the deoxyribonucleic acid (DNA) synthesis phase; labeled cells were detected in excised tumor specimens by immunoperoxidase staining using anti-BUdR monoclonal antibody. These tumors showed a wide range of BUdR labeling indices (LI's), calculated as the percentage of BUdR-labeled cells divided by the total number of cells scored, from 0.3% to 5.4%. The tumor doubling times (Td's), estimated from serial computerized tomography scans, ranged from 8 to 440 days and showed a close inverse correlation with the BUdR LI's. A semilogarithmic linear regression analysis of these values yielded a correlation coefficient of 0.99. Tumor doubling time (Td) can be estimated using the formula: Td = 500 X Exp (-0.73 X LI), where Exp signifies the natural log base. By predicting the growth rate of meningiomas, the BUdR LI may supplement histopathological diagnosis and improve both the determination of prognosis and the design of treatment modalities in individual patients.

Chromosomal analysis of neuroblastoma

Ten children with abdominal neuroblastoma were included in the study. Biopsies from the neuroblastomas were taken during surgical operations, nine from the primary tumours and one from a metastasis. Histopathology was done for diagnosis. Chromosomal cultures of neuroblastoma cells and peripheral blood lymphocytes were performed. The peripheral blood lymphocytes revealed normal chromosomal complements. The 10 tumours were in the peridiploid range with random gains or losses of chromosomes. Deletion of the short arm of chromosome number 1 distal to band p31 occurred in 6 tumours. Other structural changes and giant markers were found. It was concluded that a regulatory gene controlling the transformation gene of neuroblastoma, is present at or distal to lp31.

Clinical and biological significance of aneuploidy in human tumours

Aneuploidy is a well recognised feature of human tumours, but the investigation of its biological and clinical significance has been hampered by technological constraints. Quantitative DNA analysis reflects the total chromosomal content of tumour cells and can now be determined rapidly and reliably using flow cytometry; this has resulted in renewed interest in its potential clinical applications. This article reviews the accumulating evidence that tumour ploidy reflects the biological behaviour of a large number of tumour types and that diploid tumours in particular have a relatively good prognosis. The measurement of tumour ploidy is likely to become a valuable adjunct to the clinical and histopathological assessment of cancers.

Cytological characteristics of cultured epithelial cells from thymomas in BUF/Mna rats

Epithelial cells (ECs) from spontaneously developed thymomas in BUF/Mna rats were cultured, characterized and compared with ECs from normal thymuses. The ECs from thymomas had many more keratin filaments and PAS-positive vesicles in the cytoplasm than ECs from normal thymuses. The size and shape of ECs and their nuclei were heterogeneous and about 20% of ECs from thymomas had more than one nucleus. However, the growth rates and saturation densities of ECs from thymomas in monolayer culture were not markedly different from those of normal thymuses. The ECs from thymomas cultured in soft agar did not form any colonies. The distribution of the numbers of chromosomes found in ECs from thymomas was slightly broader than that in normal ECs, but no specific abnormalities nor marker chromosomes were noted. These findings indicate that ECs from thymomas are abnormal, but suggest that they are not malignant in nature.

Characterization of a new chromosomal marker for acute lymphoblastic leukemia from a long-term cell line

A bone marrow aspirate from a child with acute lymphoblastic leukemia (ALL) at first relapse was used to establish cell line # 697. The cultured line and marrow aspirates taken at initial diagnosis and first relapse were examined and compared. Similarities in all patterns evaluated confirmed the leukemic origin of the line. Morphologically, the cells were typically lymphoblastic. Cytochemically, they were slightly acid phosphatase-positive and negative for peroxidase, ASD chloroacetate esterase, and nonspecific esterase. Immunologically, they were found positive for common-ALL antigen (CALLA), Ia-associated antigen, terminal deoxynucleotidyl transferase (TdT), and cytoplasmic IgM (cIgM) and slightly positive for surface IgM (sIgM). Testing for Epstein-Barr virus (EBV) capsid antigen was also positive. Cytogenetic evaluations performed on initial, relapse, and cell line specimens each revealed the presence of a pseudodiploid cell line characterized by a consistent marker chromosome. GTG-, QFQ-, and RF-banding identified the marker as being derived from a translocation involving chromosomes #7 and #19: t(7;19) (q11;q13). Iso 7q, -5, -9, and +2 were also found in significant association with the marker and were viewed as demonstrating continued karyotypic evolution within the cell line. From these data, cell line #697 has been classified as a leukemic line of B-cell lineage in a transitional stage between pre-B and mature B cells.

Occurrence of in vitro tetraploidy in the heritable colon cancer syndromes

Increased in vitro tetraploidy occurred in skin cultures derived from all affected patients and some family members at risk studied in families with heritable colon cancer syndromes (15 of 16 Gardner syndrome families, three Oldfield syndrome families, and four families with heritable colon cancer syndrome without polyposis coli) but was not present in all (one Gardner syndrome family, 16 of 19 familial polyposis coli families, and two Turcot syndrome families). Seven of 97 controls, family members by marriage, showed increased in vitro tetraploidy. None of these seven had a family history of colonic cancer but four had a family history of other solid tumors. Such in vitro studies illustrated that the occurrence of in vitro tetraploidy should be determined in families rather than individuals in order to determine whether all patients clinically affected show increased in vitro tetraploidy and vertical transmission that can be documented.

Cytogenetics of neoplasia of Xiphophorus

Certain laboratory hybrid Xiphophorus fish develop heritable neoplasia. Neoplasia can also be induced in some hybrids by treatment with carcinogens. In either case the neoplasms are mediated by a "'tumor gene," that is normally controlled by linked or nonlinked "regulating genes" or both. Light and electron microscopic studies on these two types of tumors reveal important differences. The heritable tumor is a compact mass of tissue formed of densely packed melanized melanocytes often with nuclear pockets and projections. A large number of cells undergoing a process of nuclear fragmentation has been observed. The induced tumors, on the other hand, contain fewer melanized melanocytes and show a comparative increase in the amount of connective tissue. The nuclear pockets and projections commonly found in the melanocytes of the heritable tumors are not present in the melanocytes of the induced melanoma. The most important difference observed was the presence of different types of structural chromosome aberrations in the induced tumor and a total absence in the heritable ones. These anomalies seem to be epiphenomenal, and the real genetic change is subchromosomal.

Dicentric isochromosome for the long arm of chromosome #17, dic i(17q), in a patient with chronic myelogenous leukemia (CML)

Cytogenetic studies in a 33-year-old male patient with chronic myelogenous leukemia of 7 years duration revealed a so-called i(17q) chromosome marker and other cytogenetic abnormalities during the early phase of blastic crisis which were not present at diagnosis. Careful morphologic examination of this marker using G- and C-banding techniques revealed it to be a dicentric chromosome with a very short intercentromeric area. The fact that the dicentric nature of this marker was not apparent with the conventional Giemsa stain emphasizes the usefulness of the C-banding technique in defining the origin of this important cytogenetic marker.

Chromosomal anomaly of 6q in chronic myelogenous leukemia (CML)

Anomalies of chromosome 6q, along with other chromosomal anomalies, are described in the bone marrow cells of two patients with chronic myelogenous leukemia (CML). One patient a 14-year-old male, developed the karyotype 46,XY,t(1;6)(p36;q15),del(3)(q25), del(17)(p11),? inv(17)(q12q24) during blastic crisis of his disease. The other patient, a 24-year-old male, had the karyotype 46,XY,del(6)(q13),5(9;22)(q34;q11) during the early phase of his disease and evolution of i(17q) in the karyotype late in the disease.

Three or four copies of a dicentric 17q isochromosome in an acute myeloproliferative disorder

The majority of metaphases in the bone marrow of a male patient aged 72 with a rapidly evolving aleukemic erythremic myelosis had 48 chromosomes with three copies, or 49 chromosomes with four copies, of an i(17q), which was seen to be dicentric in C-banded and Giemsa-11-banded preparations. There was also loss of a chromosome No. 5 and the addition of a chromosome resembling a No. 22. The presence of multiple copies of the isochromosome is postulated to be related to the acuteness of the condition.

Cytogenetic follow-up in chronic myeloid leukemia

Twenty-six patients with Philadelphia chromosome (Ph1)-positive chronic myeloid leukaemia have been followed-up cytogenetically. Twelve patients were found to have chromosome abnormalities in addition to the Ph1, either in the chronic phase or during progression of disease. The most common abnormality observed was an additional chromosome No. 19 although trisomy 8, a second Ph1 and isochromosome 17 were also observed.

Genetic analysis of tumorigenesis: VI. Chromosome rearrangements in tumors derived from diploid premalignant Chinese hamster cells in nude mice

The chromosome constitution of CHEF/16 clones recovered from methylcellulose and of uncloned, tumor-derived CHEF/16 populations are compared. Nine of 11 clones recovered from methycellulose were initiated by diploid cells. Moreover, chromosomally diploid cells were still present in most CHEF/16 clones even after growth in anchorage-independent conditions. In contrast, none of the CHEF/16 cells recovered from tumors were diploid. Nonrandom chromosome changes were observed, but no specific chromosome alterations were consistently found in tumor-derived CHEF cells. Although CHEF/16 cells are uniformly tumorigenic in nude mice, each of 10 uncloned tumor-derived populations from inocula of 10(2), 10(4), and 10(6) CHEF/16 cells consisted of only 1-3 stemlines. Our results show that diploid CHEF/16 cells are premalignant and undergo karyotypic changes leading to successful and usually clonal establishment of tumors in nude mice.

Chromosome abnormalities, clinical and morphological manifestations in metamorphosis of chronic myeloid leukemia

Seventeen cases of chronic myeloid leukemia (CML) in metamorphosis have been investigated by cytogenetic methods. Six patients were studied in slow transformation and others in the terminal blastic phase of the disease. Of these, 3 cases were myeloid, 3 myelomonocytic, 1 megakaryoblastic, 1 promyelocytic and 4 lymphoid in their morphological and cytochemical appearance. Some correlation could be observed between the clinical, morphological, cytochemical and cytogenetic findings of the different subgroups. The results demonstrate the importance of chomosome investigations in the early diagnosis of metamorphosis and in distinguishing the different subgroups of the terminal stage of CML.

An identical translocation between chromosome 1 and 7 in three patients with myelofibrosis and myeloid metaplasia

An identical chromosome abnormality was observed in three unrelated patients with meylofibrosis and myeloid metaplasia, two of the patients showing a history of polycythaemia vera (PV) before development of the myelofibrosis. Unstimulated peripheral blood cultures showed a translocation between chromosomes 1 and 7 replacing a homologue of pair 7. It was identified by G- and C-banding as t(1;7)(7pter leads to 7p11::1p1? leads to 1qter). While the first patient also showed trisomy 21 and the third patient had some extra material on the short arm of chromosome 17, all three had trisomy 1q and monosomy 7q. Although each of these abnormalities is frequently observed separately in various haematological disorders, the combination of the two in the form of an identical translocation in three patients is an example of induced non-random cytogenetic change in myelofibrosis.

A case of AMMoL with 8/21 translocation and loss of the Y as probably secondary events

The clinical, hematological, and cytogenetic characteristics of a male patient with AMMoL are described. Before treatment a clone with the complex karyotype 45,X,del(7)(q32), t(8;21)(q22;q22) was present in the bone marrow. During partial remission induced by cytostatics, the percentage of normal cells increased, and a cell line having a 46,XY,del(7)(q32) karyotype was found. After four therapy courses, when remission was complete, only chromosomally normal cells were seen. The cytogenetic data suggest that in this case the 8/21 translocation and loss of the Y chromosome were only secondary events.

Chromosome changes in 17 human neoplasms studied with banding

Chromosome abnormalities from 17 malignancies that were studied using direct preparations and G-, Q-, and C-banding methods are presented and the findings assessed. The material used was from 6 primary cervical carcinomas, 5 primary and metastatic ovarian carcinomas and 6 other metastatic carcinomas. In general, chromosome 1 was found to be involved more frequently than the others in structural aberrations. These included short arm deletions--the most frequent marker over all the cases--long arm deletions, long arm duplications and various translocations including more complex rearrangements involving different breakpoints. Altogether ten common markers were identified among the cases, of which two were shared between two cervical carcinomas and two more, between a pair of ovarian carcinomas. The evidence in this report is in agreement with the finding of widespread involvement of chromosome 1 in malignancy, but with a particular preponderance in ovarian carcinoma.

Acute nonlymphoblastic leukemia in childhood

Cytogenetic studies have been done on a group of childhood patients over a period of 3 1/2 years in which time Giemsa trypsin banding was applied to all specimens. Fifteen of the 107 patients (14%) were diagnosed as having acute nonlymphoblastic leukemia (ANLL). Twelve of the 15 had chromosomal abnormalities. The most common was an involvement of the No. 7 chromosome which occurred in five patients. Three patients had trisomy 19. No correlation could be found between the disease subgroup and the karyotypic aberration in patients with anomalies involving a common chromosome.

Trisomy 13 in bone marrow cells in acute myelocytic leukemia and myelofibrosis

We have identified trisomy 13 in two additional patients with hematologic malignancies involving the hematopoietic stem cell: a 75-year-old female with acute myelocytic leukemia and a 64-year-old female with agnogenic myelofibrosis and myeloid metaplasia. Chromosome analysis of the direct bone-marrow preparation showed 100% of cells with trisomy 13 in the first and 10% of cells in the second. We also previously reported a patient with Ph1 negative chronic myelogenous leukemia in whom 100% of the marrow cells showed an identical trisomy. The probability of finding three such patients in our case material was calculated to be 0.05--0.08, implying that trisomy 13 may be another nonrandom chromosomal aberration associated with malignancies of hematopoietic pluri-potent stem cell.

Chromosome 8 abnormalities as components of neoplastic and hematologic disorders

Publications involving patients with any abnormality of chromosome 8 have been reviewed in detail. For the time period involved, a total of 277 cases were found, including 74 instances of congenital aneuploidy, 130 instances of acquired aneuploidy, 38 instances of congenital rearrangements, and 35 instances of acquired rearrangements. A total of 170 cases of neoplastic and hematologic disorders were included; three were associated with congenital aneuploidy, two with congenital rearrangements, and the remaining 165 with acquired aberrations. The specific disorders ranged from sideroblastic anemia through chronic and acute leukemia to solid tumors. There appears to be a definite, though non-specific correlation between congenital or acquired chromosome 8 abnormalities and the development of certain types of neoplastic growth.

Homogeneously staining regions on marker chromosomes in malignancy

Direct chromosome analysis with G-banding revealed homogeneously staining regions (HSR) in five of 16 human solid malignant tumours of different histological types. The HSR's were localized either terminally or interstitially on the marker chromosomes. The great stability of the HSR-carrying markers in the tumour cells suggests an interrelationship of malignant cell proliferation with the HSR. In a single case the HSR showed a moderate staining intensity for C-heterochromatin.

14q+ marker chromosome in an EBV-genome-negative lymph node without signs of malignancy in a patient with EBV-genome-positive nasopharyngeal carcinoma

In a patient with an EBV-genome-positive nasopharyngeal carcinoma, an EBV-genome-negative inguinal lymph node without histological evidence of malignant lymphoma or metastatic carcinoma growth was found to contain a 14q+ marker chromosome, identified as an 8;14 translocation, in all cells analyzed. This observation indicates that chromosome aberrations may precede histological signs of malignancy. The possible implication of this finding in relation to the postulated role of the 14q+ marker and lymphoma development is discussed.

Chromosome 1 abnormalities in relapse and terminal stages in childhood leukemia

Seven of 114 children with leukemia were shown to have abnormalities of chromosome 1. These included trisomy of parts of chromosome 1 as well as translocations of chromosome 1 to other chromosomes. The abnormalities were found during a relapse or terminal stage, after which the patient was refractory to therapy in all cases.

Cytogenetic studies of a male with sporadic intestinal lymphangiectasia: 45,X/46,XY mosaicism with pseudo- and hyperdiploid subpopulations in cultured tissues

45,X/46,XY mosaicism was found in peripheral blood, bone marrow, and tissue cultures of an adult male with intestinal lymphangiectasia (IL). Turner phenotype was not present; his meiotic metaphase analysis was normak, and his dermatoglyphics resembled those of his family. Ten separate tissue culture lines from three biopsies of skin and thyroid gland contained 45,X cells (14.8 to 78.3%). Autosomal aneuploidy, resulting in pseudo- or hyperdiploidy, was also present in 4.3 to 41.6% of the cells. A hyperdiploid clone with a 47,X,+10,+18 karyotype was found in 22.6% of cells in one line. A second hyperdiploid clone with a 48,X,+2,+18,+18 karyotype occurred in 7.6% of cells from another line containing a total of 41.6% pseudo- and hyperdiploid cells. Such clonal abnormalities were not typical of tissue cultures from other patients done in our laboratory. Growth of our patient's tissue cultures was subnormal, and none proliferated beyond the fourth subculture. The significance of this observation remains to be determined. Our results do not allow us to conclude whether our patient's mosaicism of somatic tissues arose during embryogenesis, or whether it originated post-natally. The secondary immunodeficiency which occurs in IL may explain persistence of cells with unusual combinations of autosomal aneuploidy in our patient's tissues.

Chromosome abnormalities in leukemia

The consistent occurrence of nonrandom chromosome changes in human malignancies suggests that they are not trivial epiphonomena. Whereas we do not understand their significance at present, one possible role which they may fulfill is to provide the chromosomally aberrant cells with a proliferative advantage as the result of alteration in the number or location of genes related to nucleic acid biosynthesis. The proliferative advantage provided by various chromosome aberrations is likely to differ in patients with different genetic constitutions.

Abnormalities of chromosome No. 1: significance in malignant transformation

Studies of human hematologic malignancies have provided sufficient data not only for the identification of nonrandom abnormalities of whole chromosomes, but also for determination of the specific chromosome regions involved. In clonal aberrations leading to an excess of chromosome No. 1, or a partial excess of No. 1, trisomy for bands 1q25 to 1q32 was noted in the myeloid cells obtained from every one of 35 patients who had various disorders, such as acute leukemia, polycythemia vera, or myelofibrosis. Similar chromosome changes were a consistent finding in various solid tumors as well. This rearrangement was not the result of a particularly fragile site in that region of the chromosome, since the break points in reciprocal translocations that involve No. 1 occurred almost exclusively in the short arm. The nonrandom chromosome changes found in neoplastic cells can now be correlated with the gene loci on these chromosomes or chromosome segments as an attempt is made to identify specific genes that might be related to malignancy.

Chromosome studies in preleukemic states. IV. Myeloproliferative versus cytopenic disorders

The prognostic value of marrow chromosome studies was examined in 112 "preleukemic" patients followed for at least one year or until death. Based on recent definitions, 49 patients were classified as myeloproliferative disorders (MPD) (polycythemia vera, myelofibrosis, undifferentiated myeloproliferative disorder, essential thrombocythemia), and 58 as cytopenic states (refractory anemia, pancytopenia). In each group, approximately one-third had a chromosomally-abnormal clone. For MPD, this had little predictive value, but in the cytopenias, 77% with a cytogenetic abnormality developed leukemia versus 39% without. Twelve cytopenic patients had multiple alterations involving more than 2 chromosomes and 11 died within 6 months, 9 with leukemia. Such patients may warrant consideration for aggressive chemotherapy before the appearance of clinical leukemia. Banding studies did not reveal any specific chromosome abnormalities consistently associated with these various preleukemic disorders, or with progression to leukemia, but nonrandom alterations were noted involving chromosomes 1, 5, 7-9, and 20 in the MPD group, and chromosomes 6 and 16 in the cytopenic patients. Correlation of these data with other reports indicates that certain cytogenetic abnormalities involving specific segments of the human genome confer a selective growth advantage on hemic clones which may present clinically as either preleukemia or leukemia.

Chromosome changes (trisomy 15) in murine T-cell leukemia induced by 1,12-dimethylbenz(a)anthracene (DMBA)

The banding pattern of DMBA-induced leukemias in C57BL/6 mice revealed a very constant chromosome pattern: the presence of trisomy 15 in almost all leukemic cells. This finding strongly suggests that chromosome 15 trisomy is the first detectable specific chromosome change associated with the development of DMBA-induced T-cell lymphomas. A similar association was previously shown with regard to development of radiation-leukemia-virus-induced T-cell lymphoma. It is conceivable that in tumors of diverse etiologies common cytogenetic changes may appear in the same common target-cell precursor, by a process of the "convergent microevolution" type.

[Chromosomal abnormalities in human neoplasia (author's transl)]

Multiple connections exist between chromosomal aberrations and malignant tumors. It is the aim of the present article to summarize the data known so far in view of i) cancer-prone chromosome abnormalities, ii) chromosome abnormalities related to tumors and iii) chromosome abnormalities related to carcinogens. In some instances it seemed useful to discuss the findings in man in connection with the results of in vitro experimental data.

Trisomy of 1q in preleukaemia with progression to acute leukaemia

Marrow cells from an untreated man with preleukaemia were found to have trisomy for the long arm of chromosome 1 which was translocated to the end of the long arm of number 11, i.e., 46,XY, -11,+t (1:11) (q11 or q12; q25). The same abnormality was found in metaphases from 8 individual granulocytic colonies. With development of acute myelomonocytic leukaemia, in addition to the basic chromosome abnormality, trisomy of chromosome 8 and an extra chromosome number 19 with partial deletion were found. Fibroblasts grown from marrow biopsy material showed a normal diploid complement, 46,XY.

Reciprocal translocation and the Philadelphia chromosome

We examined metaphases from three patients with chronic myeloid leukaemia and a typical Philadelphia chromosome with one chromosome 9 as the recipient to determine whether the 9q+22q- translocation is reciprocal. Good quality G-banded photographs of the chromosomes concerned were subjected to light absorption density analysis. This provided enlarged tracings corresponding to the relevant chromosome regions and so facilitated accurate measurement. This technique has unambiguously shown that the typical Philadelphia chromosome results from a reciprocal translocation and that probably no material is gained or lost in the exchange. Furthermorein a total of six patients for whom sequential G and C banding was performed, the chromosome 9 with the largest block of centromeric heterochromatin received the translocated material. We offer tentative explanations for this curious observation.

Camptomelic dwarfism associated with XY-gonadal dysgenesis and chromosome anomalies

We have studied two female newborns with comptomelic dwarfism, XY-gonadal dysgenesis and chromosome anomalies. The preponderance of "females" among the hitherto reported cases of this allegedly autosomal recessive form of lethal drawfism may be due to an increased incidence of an associated XY-gonadal dysgenesis.