Charlotte Örndal

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.

Cytogenetic intratumor heterogeneity in soft tissue tumors

Multiple (two to seven) samples, obtained from the same surgical specimen or at different occasions, were analyzed in 54 benign and malignant soft tissue tumors, to investigate cytogenetic clonal evolution. In 28 tumors only normal karyotypes were found. Ten tumors had abnormal karyotypes, but were noninformative, most often due to a high level of karyotypic complexity or great cell-to-cell variation. Sixteen tumors were informative: four (leiomyosarcoma, liposarcoma, malignant Schwannoma, and a benign mesenchymal tumor, probably leiomyoma) had identical karyotypes in different samples, whereas the remaining 12 tumors (seven malignant fibrous histiocytomas [MFH], two leiomyosarcomas, two liposarcomas, and one synovial sarcoma) displayed intersample heterogeneity. Also, intrasample heterogeneity was detected; more than one clone was found in 21 of 73 samples with aberrations from 26 tumors. The different clones were related in all cases except two. In seven cases, samples from different occasions were studied, and clonal evolution could be evidenced in five of them, whereas in two cases the karyotypes remained unchanged. The results indicate that the acquisition of ring chromosomes is an early event in the development of MFH and possibly also pleomorphic liposarcoma. The findings, together with previous data, also indicate that rearrangements of 19p13 are late events in the progression of pleomorphic sarcomas. The overall conclusion from this study is that cytogenetic heterogeneity is common in soft tissue tumors, and that this might influence the evaluation of cytogenetic and molecular genetic findings.

Chromosomal Abnormality T(9;22)(Q22;Q12) In an Extraskeletal Myxoid Chondrosarcoma Characterized By Fine Needle Aspiration Cytology, Electron Microscopy, Immunohistochemistry and Dna Flow Cytometry

A multidisciplinary approach was taken to characterize a soft tissue tumour. In smears prepared from aspirated material, uniform tumour cells, embedded in a myxoid matrix and partly arranged in a lace‐like pattern, were found. Histopathology showed a lace‐like pattern of cells in a matrix of hyaluronidase‐stable mucins. Cytoplasmic positivity for S‐100 protein was found in some tumour cells. Electron microscopic analysis revealed intracisternal aggregates of microtubules. All these features are consistent with the diagnosis of extraskeletal myxoid chondrosarcoma (EMC). DNA flow cytometry showed a diploid DNA content. Cytogenetic examination revealed the tumour karyotype 45, XY, t(2;11)(q31;p15), t(9;22)(q22.3;q12), dic(13;22)(p11;p13). Because similar 9;22‐translocations have been described in two other cases of EMC, we conclude that t(9;22)(q22–31;q11–12) is a specific rearrangement in this tumour type. Cytogenetic analysis may thus be of diagnostic value in the examination of tumours with this and similar histologies.

Simple numerical chromosome aberrations in well-differentiated malignant epithelial tumors.

Cytogenetic analysis of four well-differentiated malignant epithelial tumors revealed primary clones with only numerical abnormalities. The karyotypes were 49,XX, +5, +5, +7, +7, -17/50,XX, +5, +5, +7, +7, -17, +r in an adenocarcinoma of the lung; 47,XX, +3/47,XX, +5/47,XX, +7 in a squamous cell carcinoma of the epiglottis; 47,XX, +5/48,XX, +5, +10 in a squamous cell carcinoma developing in an ovarian dermoid cyst; and 52,XX, +5, +7, +8, +14, +15, +21 in a seropapillary ovarian adenocarcinoma. Also, in previously published cases exclusively numerical aberrations were much more common in highly differentiated epithelial tumors (22/74) than in moderately to low-differentiated carcinomas (13/281). Our findings and the literature data thus agree with a developmental scheme in which numerical changes, possibly reflecting an early-onset genomic instability in the tumor cells, may precede massive structural anomalies in the gradual malignization of epithelial tumors.

Chromosome aberrations and cytogenetic intratumor heterogeneity in chondrosarcomas

Clonal chromosome aberrations identified after short-term culture are presented for 13 chondrosarcomas; in 5 cases both the primary tumors and local recurrences were studied. The stemline chromosome number was hypodiploid or hyperhaploid in 9 tumors. The most frequent numerical anomalies were, in falling order of frequency, loss of chromosomes Y, 10, 13, and 6, and gain of chromosomes 7 and 20. No recurrent structural rearrangement was found, but chromosome bands 5q13, 1q21, 7p11, and 20q11 were each involved in three different rearrangements. Karyotypic heterogeneity was assessed in two different ways: as the presence of more than one clone in one sample and as the presence of different clones in different samples from the same surgical specimen. Clonal karyotypic evolution was demonstrated in 6 of the 7 cases in which two or more samples could be investigated. All 6 showed intersample heterogeneity. Intrasample heterogeneity was found in only 5 of the 28 samples with aberrations. By comparing the incidences of the nonrandomly occurring aberrations in stemlines and sidelines in the heterogeneous tumors, it was possible to conclude that loss of chromosome 13 and rearrangement of band 5q13 were early events in the clonal evolution.

Chromosomal evolution and tumor progression in a myxoid liposarcoma

A myxoid liposarcoma showed macroscopic, histologic, and cytogenetic heterogeneity. In one of three myxoid nodules and in the surrounding lipoma-like tumor tissue, the translocation t(12;16)(q13;p11), known to be specific for myxoid liposarcoma, was found as the sole chromosomal abnormality. In the other two nodules, additional rearrangements involving chromosomes 1, 12, and 16 were found. These aberrations were probably secondary to the primary t(12;16), and are cytogenetic evidence of clonal evolution. The complex chromosome aberrations were present in those tumor parts that had more malignant histology, indicating that the acquisition of secondary chromosomal aberrations parallels the histologic manifestations of tumor progression.

Parathyroid adenoma with t(1;5)(p22;q32) as the sole clonal chromosome abnormality

Cytogenetic investigation of short-term cultures from a parathyroid adenoma revealed a t(1;5)(p22;q32) as the sole clonal chromosomal aberration. Karyotypic abnormalities have not previously been described in this tumor type.

Near-Haploid Clones in a Malignant Fibrous Histiocytoma

Near-haploid solid tumors are very rare. In a storiform-pleomorphic malignant fibrous histiocytoma (MFH) of bone, we found three cell populations: one with a near-haploid, a second with a near-diploid, and a third with a near-tetraploid chromosome number. The near-haploid cells had few structural rearrangements: i(12p) and t(13q21q) in one clone, and these two and an additional t(19;?)(p11;?) in another clone. One structurally normal copy of all chromosomes was also present, except that the only chromosome 13 was involved in the t(13q21q). There were also two near-diploid clones, one without the t(19;?) and one with a single copy of this derivative chromosome. This is the first tumor with i(12p) among bone and soft tissue tumors.