Complex karyotypic anomalies in a bizarre leiomyoma of the uterus

The Diverse Effects of Complex Chromosome Rearrangements and Chromothripsis in Cancer Development

In recent years, enormous progress has been made with respect to the identification of somatic mutations that contribute to cancer development. Mutation types range from small substitutions to large structural genomic rearrangements, including complex reshuffling of the genome. Sets of mutations in individual cancer genomes may show specific signatures, which can be provoked by both exogenous and endogenous forces. One of the most remarkable mutation patterns observed in human cancers involve massive rearrangement of just a few chromosomal regions. This phenomenon has been termed chromothripsis and appears widespread in a multitude of cancer types. Chromothripsis provides a way for cancer to rapidly evolve through a one-off massive change in genome structure as opposed to a gradual process of mutation and selection. This chapter focuses on the origin, prevalence and impact of chromothripsis and related complex genomic rearrangements during cancer development.

Cytogenetics of Mesenchymal Tumors of the Female Genital Tract

A great diversity of chromosome alterations have been reported in mesenchymal tumors of the female genital tract, particularly in the uterus. Some of these alterations specifically identify a certain tumor type. Cytogenetic studies on benign proliferations have not only demonstrated clonal chromosome changes, but have also pointed out clustering of aberrations to specific chromosome regions. For example, distinct cytogenetic subgroups have been described in uterine leiomyomas with overlapping histologic features. These findings may ultimately correlate with specific parameters, such as course of the disease, response to therapy, and recurrence. Moreover, such data may give a clue to an understanding of the biologic basis for distinctive behavior of benign versus malignant mesenchymal proliferations. No specific chromosomal abnormalities have been described in malignant mesenchymal tumors, with the exception of low-grade endometrial stromal sarcomas. This article reviews the information currently available on genetic changes in mesenchymal tumors of the female genital tract and, more specifically, those reported in the uterus, where they have been more frequently studied.

High frequency of telomeric associations and chromatid exchanges and breaks in human ovarian carcinoma

Cytogenetic analysis of an unselected series of twenty human serous adenocarcinomas and undifferentiated carcinomas of the ovary revealed the presence of telomeric associations (tas) and unstable chromosomal aberrations, including chromatid-type exchanges (cte) and breaks (ctb) in high proportion of tumors studied. Tas and cte & ctb were present in 75% and 55% of tumors, respectively. Involvement of different chromosome telomeres in tas seemed to be random. This is the first report describing telomeric associations in ovarian cancer. Our findings suggest that the frequency of extensive spontaneous chromosome breakage in ovarian carcinoma may be higher than that reported in the literature.

Uterine leiomyomata with deletions of Ip represent a distinct cytogenetic subgroup associated with unusual histologic features

Cytogenetic analysis of uterine leiomyomata (UL) shows that about 40% of these benign tumors have simple, clonal chromosomal rearrangements. In contrast, their presumed malignant counterpart, leiomyosarcomas (LMSs), typically has complex numerical and structural abnormalities. Several variants of benign uterine smooth-muscle tumors are defined by histologic phenotypes intermediate between typical UL and LMS, and currently, little is known about their cytogenetic and molecular genetic features. From a subset of more than 800 karyotyped ULs, we identified a group of nine cases exhibiting near-diploid karyotypes with loss of almost the entire short (p) arm of chromosome 1 [i.e., del(1)(p11p36)]. Loss of 1p was often associated with other aberrations, particularly loss of chromosomes 19 and/or 22. Of eight UL for which the histologic diagnosis was known, four were diagnosed as cellular UL; one displayed both hypercellularity and nuclear atypia. Loss of heterozygosity (LOH) analysis for chromosomal regions 1p36.23 and 1p21.1 demonstrated allelic loss for either a portion or the majority of 1p in 5 of 10 additional archival UL diagnosed with either cellular or atypical histology. RNA from two UL with loss of 1p was profiled using Affymetrix GeneChips, and those profiles were compared to our previously reported smooth-muscle tumor expression profile. The transcriptional profiles of tumors with 1p deletion were more similar to those of leiomyosarcoma than to profiles of myometrium and UL, as determined by hierarchical cluster analysis. Comparison of the transcriptional profiles for UL with and without 1p-- revealed 53 genes with differential regulation. Loss of 1p appears to define a subgroup of UL distinct from those previously recognized. Furthermore, 1p-- appears to be associated with a specific histologic phenotype. The similarity between the transcriptional profiles of LMS and UL with 1p-- suggests the possibility of a common pathogenetic mechanism.

Frequent loss of heterozygosity for chromosome 10 in uterine leiomyosarcoma in contrast to leiomyoma

Distinction of malignant uterine leiomyosarcomas from benign leiomyomas by morphological criteria is not always possible. Leiomyosarcomas typically have complex cytogenetic abnormalities; in contrast, leiomyomas have simple or no cytogenetic abnormalities. To understand better the biological distinction(s) between these tumors, we analyzed two other potential markers of genomic instability, loss of heterozygosity (LOH) and microsatellite instability. We examined archival materials from 16 leiomyosarcomas and 13 benign leiomyomas by polymerase chain reaction for 26 microsatellite polymorphisms. Markers were selected based on previous reports of cytogenetic or molecular genetic abnormalities in leiomyosarcomas or leiomyomas and surveyed chromosomes 7, 9, 10, 11, 12, 14, 15, 16, 18, 21, and X. LOH for markers on chromosomes 15, 18, 21, and X was infrequent in leiomyosarcomas (1 of 6 tumors for each chromosome) and not observed for markers on chromosomes 7, 9, 11, 12, 14, or 16. Interestingly, 8 of 14 (57.2%) informative leiomyosarcomas had LOH for at least one marker on chromosome 10 and involved both chromosomal arms in 45.5% (5 of 11). In contrast to leiomyosarcomas, LOH for chromosome 10 was not found in 13 benign leiomyomas. Microsatellite instability was found infrequently in leiomyosarcomas and not detected in leiomyoma. Clinicopathological features (eg, atypia, necrosis, and clinical outcome) did not appear to correlate with LOH for chromosome 10. In contrast to other chromosomes studied, LOH on chromosome 10 was frequent in leiomyosarcomas and absent in benign leiomyomas.

Deletion of HMG17 in uterine leiomyomas with ring chromosome 1

Uterine leiomyomas are characterized by several subgroups with characteristic chromosomal aberrations, mainly 12q14-15, 6p21, or interstitial deletions of chromosomes 3 and 7. For the first two subgroups, aberrations of the HMGIC and HMGIY genes have been described and are held responsible for tumor initiation. For other subgroups no molecular findings have been described as of yet. We focus here on a smaller subgroup of uterine leiomyomas with a ring chromosome 1 either as the only karyotypic deviation or occurring along with other abnormalities. In the p-arm of chromosome 1 HMG17, another member of the high-mobility group of proteins has been localized to the short arm of chromosome 1 (1p35) with two PAC clones on metaphase spreads of a uterine leiomyoma ring(1). Hybridization signals for these probes were not detected within the ring chromosome consistent with loss or deletion of HMG17. These findings suggest that HMG17 does not play a mechanistic role in leiomyoma similar to that observed with other high-mobility proteins.

Cytogenetics of tumors of soft tissue and bone. Implication for pathology

Pathologists should be aware of the existence of diagnostically useful chromosomal rearrangements in several soft tissue and bone tumors. They include rearrangement of 8q12 in lipoblastomas, ring chromosomes in atypical lipomas, ring and giant marker chromosomes in well differentiated liposarcomas, t(12;16)(q13;p11) in myxoid liposarcomas, rearrangement of 7p21-22 in low-grade endometrial stromal sarcomas, t(2;13)(q37;q14) in alveolar rhabdomyosarcomas, t(X;18)(p11.2;q11.2) in synovial sarcomas, t(12;22) (q13;q13) in clear cell sarcomas, t(11;22)(q24;q12) in Ewing's sarcomas and peripheral neuroepitheliomas, and t(9;22)(q21-31;q11-12) in extraskeletal myxoid chondrosarcomas.

Supernumerary ring chromosomes in five bone and soft tissue tumors of low or borderline malignancy

Five tumors (two myxoid malignant fibrous histiocytoma, two dermatofibrosarcoma protuberans, and one parosteal osteosarcoma) with ring chromosomes as the sole cytogenetic anomaly or as the only structural rearrangement were observed in a series of 60 karyotypically abnormal, nonlipogenic bone and soft tissue tumors (BST). All five tumors were of borderline or low malignancy. These findings support the suggestion that supernumerary ring chromosomes as the sole structural chromosomal aberration are not associated with any particular histopathologic diagnosis but may characterize a group of BST of borderline or low malignancy.

Chromosome analysis of 96 uterine leiomyomas

From September 1989 to May 1990, we attempted cytogenetic analysis on 96 uterine leiomyomas removed from 64 women. Of the 90 tumors in which analysis was successful, 59 had a normal karyotype while 31 had clonal abnormalities. The most common aberration (13 tumors) was 7q-, mostly del(7)(q21.2q31.2); in two tumors with +12 and t(12;14) as the primary abnormalities, the 7q- was obviously a secondary change since it was found only in a subclone. A t(12;14)(q14-15;q23-24) was detected in two tumors, complex aberrations involving both 12q14-15 and 14q23-24 were also present in two, and rearrangements of 12q without concomitant 14q changes were seen in another two myomas. Rearrangements of 6p were present in five tumors, and trisomy 12 was found in two. More than one abnormality could be detected in 17 leiomyomas. Evidence of clonal evolution in the form of subclones was found in eight tumors, all of which were cellular and had histologically detectable mitotic activity. In addition to their clonal complexity, these myomas also frequently exhibited clonal telomeric associations (four tumors) and ring chromosome formation (three tumors; twice affecting chromosome 1). Monosomy 22 occurred as a secondary abnormality in three tumors; it, too, may reflect a preferred pathway in the karyotypic evolution of uterine leiomyomas.

Parallel karyotypic evolution and tumor progression in uterine leiomyoma

Cytogenetic evidence of clonal evolution was detected in five uterine leiomyomas. In two tumors, two clones were found, the third tumor had four, the fourth had nine, and the fifth had 12 clones. The first tumor had trisomy 12 as the primary anomaly and a sideline that also contained a del(7)(q21q31). Both clones of the second tumor had three structural changes in common but differed by the presence in the more advanced clone of an inv(7)(q31q34). Two cytogenetically unrelated pairs of clones were seen in the third tumor. One clone had a stemline of 46 and an r(1); a sideline had developed through duplication of this clone. The other pair had a del(7)(q21q31) in common. The last two tumors both had t(12;14)(q14-15;q23-24) as the primary abnormality. They also had a high frequency of telomeric associations that involved certain chromosome arms only. One of the secondary changes in the fourth tumor was a del(7)(q21q31); the principal secondary change in the fifth case was a ring chromosome 1 of variable size in the different clones. The analysis of these five uterine leiomyomas and the collation of the results with previously obtained data lead us to conclude that del(7)(q21q31) is secondary to t(12;14) and + 12 in this tumor type, and that ring formation involving chromosome 1 material, often with duplication of segments, is a common phenomenon during clonal evolution. The fact that the tumors were classified as cellular and had an increased mitotic rate indicates a parallel development between histologically detectable tumor progression and cytogenetically recognizable clonal evolution in uterine leiomyomas.

Characteristic chromosome abnormalities, including rearrangements of 6p, del(7q), +12, and t(12;14), in 44 uterine leiomyomas

The cytogenetic analysis of 224 leiomyomas from 138 patients is presented. An insufficient number of mitoses was found in 35 tumors, normal karyotypes in 145, and clonal chromosome aberrations were detected in 44. The three previously identified cytogenetic subgroups were all represented in this series: del(7) (q21.2q31.2) was found in 11, trisomy 12 in five, and t(12;14)(q14-15;q23-24) in one leiomyoma. Rearrangements of 6p, including deletions, inversions, and various translocations, were found in eight tumors, thus delineating a new cytogenetic subgroup of uterine leiomyoma. The remaining 21 karyotypically abnormal tumors had nonrecurrent changes. One leiomyoma had two cytogenetically unrelated clones characterized by del(7)(q21.2q31.2) and +12. Karyotypic changes in two separate leiomyomas from the same uterus were identified in five patients; in three of them, different anomalies were found in the two tumors, whereas cytogenetically identical aberrations - del(7q) and dic(21;22) - were detected in two macroscopically discrete tumors. These findings suggest that whereas some multiple leiomyomas originate independently, others may be derived from the same neoplastic clone.

Complex chromosome rearrangements involving 12q14 in two uterine leiomyomas

Cytogenetic analysis of short-term cultures from 10 uterine leiomyomas revealed normal karyotypes in 8 and clonal complex chromosome rearrangements in 2 tumors. In both leiomyomas with clonal abnormalities, 12q14, but not 14q22-24, was involved in translocations with 1q43 in one tumor and with 12q24 in the other. Additional chromosome abnormalities were found in both cases: 1-5 rings and monosomy of chromosome 9 in case 1, and complex numerical and structural abnormalities of chromosomes 1, 6-8, 11, 13, 16, 17, and 22 in case 2. The consistent cytogenetic rearrangement of 12q14 in uterine leiomyomas, sometimes without concomitant 14q changes, indicates that a gene of critical importance for leiomyoma development may be found in this band.

Uterine leiomyoma cytogenetics

Uterine leiomyoma--a benign smooth muscle tumor--has recently been found to contain tumor-specific chromosome aberrations. Although only normal karyotypes were detected in 50 to 80% of cytogenetically investigated tumors, 104 leiomyomas with karyotypic aberrations have already been reported. At least four cytogenetically abnormal subgroups have been identified thus far, characterized by rearrangements of 6p, del(7)(q21.2q31.2), +12, and t(12;14)(q14-15;q23-24). The remaining abnormal tumors have had various nonrecurrent anomalies. Secondary karyotypic rearrangements, sometimes including ring chromosomes, have been found in one-third and reflect clonal evolution. Occasional leiomyomas have contained multiple numerical and structural rearrangements. Though benign, these cytogenetically grossly aberrant tumors often displayed more atypical histological features than are usually seen in leiomyoma. Multiple leiomyomas have been investigated from 69 patients, with detection of chromosome anomalies in at least two separate tumors from the same uterus in ten cases. In half of these patients unrelated aberrations were found in different leiomyomas from the same uterus. On other occasions the aberrations were identical, indicating that although some uterine leiomyomas originate independently, others may develop by intra-myometrial spreading from a common neoplastic clone. Some common features are discernible between the karyotypic pictures of uterine leiomyoma and angioleiomyoma; rearrangements of 6p, 13q, and 21q have been described in both tumor types. The cytogenetic similarities so far detected between leiomyoma and the malignant muscle tumors--leiomyosarcoma and rhabdomyosarcoma--are few and may be fortuitous. The cytogenetic profiles of leiomyoma and lipoma are strikingly similar; both tumor types have nonrandom rearrangements of 12q13-15, t(12;14) in leiomyoma and t(3;12) in lipoma, as well as variant rearrangements of the same 12q segment. Both also have cytogenetic subgroups characterized by changes in 6p and ring chromosomes. Finally, karyotypic similarities exists also between leiomyoma and pleomorphic adenoma of the salivary gland, which includes a subset of tumors with anomalies of 12q13-15, and with myxoid liposarcoma, which has t(12;16)(q13;p11) as a tumor-specific rearrangement.