Histologic Subtypes Of Sarcomas Research Articles

Nationwide incidence of sarcomas and connective tissue tumors of intermediate malignancy over four years using an expert pathology review network.

Since 2010, nationwide networks of reference centers for sarcomas (RREPS/NETSARC/RESOS) collected and prospectively reviewed all cases of sarcomas and connective tumors of intermediate malignancy (TIM) in France. The nationwide incidence of sarcoma or TIM (2013-2016) was measured using the 2013 WHO classification and confirmed by a second independent review by expert pathologists. Simple clinical characteristics, yearly variations and correlation of incidence with published clinical trials are presented and analyzed. Over 150 different histological subtypes are reported from the 25172 patients with sarcomas (n = 18712, 74,3%) or TIM (n = 6460, 25.7%), with n = 5838, n = 6153, n = 6654, and n = 6527 yearly cases from 2013 to 2016. Over these 4 years, the yearly incidence of sarcomas and TIM was therefore 70.7 and 24.4 respectively, with a combined incidence of 95.1/106/year, higher than previously reported. GIST, liposarcoma, leiomyosarcomas, undifferentiated sarcomas represented 13%, 13%, 11% and 11% of tumors. Only GIST, as a single entity had a yearly incidence above 10/106/year. There were respectively 30, 64 and 66 different histological subtypes of sarcomas or TIM with an incidence ranging from 10 to 1/106, 1-0.1/106, or < 0.1/106/year respectively. The 2 latter incidence groups represented 21% of the patients with 130 histotypes. Published phase III and phase II clinical trials (p<10-6) are significantly higher with sarcomas subtypes with an incidence above 1/106 per. This nationwide registry of sarcoma patients, with exhaustive histology review by sarcoma experts, shows that the incidence of sarcoma and TIM is higher than reported, and that tumors with a very low incidence (1<106/year) are less likely to be included in clinical trials.

Nationwide incidence of sarcomas and tumors of intermediate malignancy in the NETSARC network with central pathology review: Correlation with published clinical research.

11560 Background: Since 2010, presentation to a designated sarcoma tumor board and pathological review by an expert network are mandatory for sarcoma patients in France. NETSARC+ (merging the 3 initial RREPS, RESOS &amp; NETSARC) collected prospectively all cases of reviewed sarcomas and tumors of intermediate malignancy (TIM) nationwide. We report on the incidence of subtypes according to WHO classification from 2013 to 2016. Methods: Sarcoma expert pathologists reviewed samples were all prospectively integrated in the database; the results using the latest WHO classification are presented for the years 2013 to 2016, including yearly variations. Correlation of the incidence of each histotype with dedicated published clinical trials was conducted. Results: 139 different histological subtypes are reported among the 25172 patients with sarcomas (n = 18710, 64%) or TIM (n = 6460, 36%), respectively n = 5838, n = 6153, n = 6654, and n = 6527 yearly from 2013 to 2016. Over these 4 years, the observed yearly incidence of sarcomas, TIM, and all was therefore 79.7, 24.9 and 95.1/10e6/year, above that previously reported. GIST, liposarcoma, leiomyosarcomas, undifferentiated sarcomas represented 13%, 13%, 11% and 11% of all sarcomas. Only GIST, as a single entity exceeded a yearly incidence above 10/million per year. There were respectively 30, 63 and 66 different histological subtypes of sarcomas or TIM (single entities or lumped together, e.g. MPNST, or vascular sarcomas...) with an incidence ranging from 10 to 1/10e6/year, 1-0.1/10e6 per year, or &lt; 0.1/10e6/year respectively. The 2 later “incidence groups” included 21% of the patients. The incidence of 8 histotypes varied significantly over this 4 years. Patients with tumors with an incidence above 1/10e6 per year have significantly higher numbers of dedicated published phase III and phase II clinical trials (p &lt; 10e-6). Conclusions: This nationwide registry of sarcoma patients with an histology reviewed by sarcoma experts shows that the incidence of sarcoma and TIM is higher than previously reported, may vary over years for some histotypes, and that tumors with an incidence &lt; 10e6 have a much lower access to clinical trials.

Overview of « druggable » alterations by histological subtypes of sarcomas and connective tissue intermediate malignancies.

We summarize herein the literature data about molecular targeted therapies in sarcomas and conjunctive tissue intermediate malignancies. For each clinical setting, the level of evidence, the mechanism of action and the target are described. The two major axes include (i) identification of subgroups of tumors with druggable alteration irrespective of the histological diagnosis (e.g. NTRK), and (ii) druggable target of pathway related to the physiopathology of the tumor: denosumab and bone giant cell tumor, imatinib and soft tissue giant cell tumor, mTOR inhibitor and PECOMA.

Nationwide Incidence of Sarcomas and Tumors of Intermediate Malignancy in France

Background: Since 2010, presentation to a designated sarcoma tumor board and pathological review by an expert network are mandatory for sarcoma patients in France. NETSARC+ (merging the 3 initial RREPS, RESOS & NETSARC) collected prospectively all cases of reviewed sarcomas and tumors of intermediate malignancy (TIM) nationwide. We report on the incidence of subtypes according to WHO classification from 2013 to 2016. Methods: Sarcoma or TIM confirmed by review of expert sarcoma pathologists were all prospectively integrated in the database; the results using the latest WHO classification are presented for the years 2013 to 2016, including yearly variations. Correlation of the incidence of each histotype with dedicated published clinical trials was conducted. Results: 139 different histological subtypes are reported among the 25172 patients with sarcomas (n = 18710, 64%) or TIM (n = 6460, 36%), respectively n = 5838, n = 6153, n = 6654, and n = 6527 yearly from 2013 to 2016. Over these 4 years, the observed yearly incidence of sarcomas, TIM, and both was therefore 79.7, 24.9 and 95.1/106/year, above that previously reported. GIST, liposarcoma, leiomyosarcomas, undifferentiated sarcomas represented 13%, 13%, 11% and 11% of all sarcomas. Only GIST, as a single entity exceeded a yearly incidence above 10/million per year. There were respectively 30, 63 and 66 different histological subtypes of sarcomas or TIM (single entities or lumped together, e.g. MPNST, or vascular sarcomas...) with an incidence ranging from 10 to 1/106/year, 1-0.1/106 per year, or < 0.1/106/year respectively. The 2 later “incidence groups” included 21% of the patients. The incidence of 8 histotypes varied significantly over this 4 years. Patients with tumors with an incidence above 1/106 per year have significantly higher numbers of dedicated published phase III and phase II clinical trials (p < 10-6). Conclusions: This nationwide registry of sarcoma patients with an histology reviewed by sarcoma experts shows that the incidence of sarcoma and TIM is higher than previously reported, may vary over years for some histotypes, and that tumors with an incidence < 10e6 have a much lower access to clinical trials. Funding Statement: NetSARC (INCA & DGOS) and RREPS (INCA & DGOS), RESOS (INCA & DGOS) and LYRICAN (INCA-DGOSINSERM 12563), Institut Convergence PLASCAN (17-CONV-0002), Association DAM’s, Ensemble contre Le GIST, Eurosarc (FP7-278742), la Fondation ARC, Infosarcome, InterSARC (INCA), LabEx DEvweCAN (ANR-10-LABX-0061), Ligue de L’Ain contre le Cancer, La Ligue contre le Cancer, EURACAN (EC 739521) funded this study. Declaration of Interests: The funders had no role in the study design, data collection, data analysis, data interpretation, or writing of the report.

The Vanderbilt staging system for retroperitoneal sarcoma: a validation study of 6857 patients from the National Cancer Database

The Vanderbilt staging system for retroperitoneal sarcoma incorporates information regarding the histologic subtype of sarcoma and outperforms the 7th and 8th editions of the AJCC staging systems by several different statistical criteria. The current study was performed using an independent patient cohort from the National Cancer Database (n = 6857) to validate this proposed staging system. Each staging system was assessed for degree of discrimination by pairwise comparisons of adjacent stage categories. Predictive accuracy of 5-year overall survival was performed by comparison of areas under receiver operating characteristic curves generated from logistic regression. Three different concordance indices (Harrell's c, Somers' D, and Gönen and Heller's K) were calculated using bootstrap methods. Amount of variation in observed outcomes explained by each staging system was assessed using O'Quigley's ρ2k and Royston's R2. Bayesian information criteria were also assessed as measures of model fit. The revised AJCC 8th edition T categories were not effective in categorizing risk of death. The Vanderbilt staging system showed the best discrimination between adjacent tumor stages, highest predictive accuracy for 5-year overall survival, a higher degree of concordance with and explained variation of clinical outcomes, and resulted in the best fitting regression model. These results obtained with an independent dataset validate the Vanderbilt staging system for retroperitoneal sarcoma and demonstrate its superiority in risk stratification over current and prior editions of the AJCC staging system.

Sarcomas With Complex Genetic Changes

Sarcomas With Complex Genetic Changes

Clinical trial design methodologies for advanced sarcoma therapy

AbstractSarcomas are rare and heterogeneous mesenchymal tumors affecting connective tissue. For many years, doxorubicin-based chemotherapy has been the main systemic therapy option for patients with metastatic soft tissue sarcoma. This ‘one size fits all’ approach has led to marginal benefit, but the introduction of tyrosine kinase inhibitors in gastrointestinal stromal tumors has shown that sub-type-specific, molecularly targeted therapy can lead to significant advances. Next generation sequencing has led to the discovery of the biologic nature of many histological sub-types of sarcomas, and now an emphasis has been placed on assessment of novel therapies for each sub-group. However, the transition into the clinic is both challenging and protracted due to the rarity and heterogeneity of these tumors. The high failure rate of phase III trials in oncology has shown that clinical trials can be difficult to run, especially in rare forms of cancer like sarcomas. In this review, the authors provide an evaluati...

High-dose ifosfamide (HDI) in metastatic synovial sarcoma: The Institut Gustave Roussy experience.

10044 Background: Synovial sarcoma (SS) is one of the most chemo-sensitive histological subtypes of sarcoma but with a dismal prognosis. In metastatic setting, Anthracyclin/ifosfamide-containing chemotherapy (CT) regimen is the gold standard of treatment in front-line therapy. Patients (pts) with resistant diseases are candidates to investigational drugs or higher dose ifosfamide regimen in selected pts. Methods: Pts treated in our institution, with histological confirmation of advanced SS, adequate organ function and in good condition (PS≤2) were included in this retrospective analysis. Pts who progressed after 1–2 chemotherapy lines received High-dose ifosfamide (HDI) in the form of 4 g/m2 daily (over 24 hours CI) for 3 days for a total dose of 12 g/m2; cycles were given with growth factor support and were repeated every 3 weeks. The primary endpoints were PFS and overall response rate (ORR); the secondary endpoints OS and toxicity profile. AE were assessed by NCI-CTC v. 3.0. Results: 34 pts (21 males) with a median age of 39 years (range 19-66) received this HDI regimen. PS was 0-1 in 90%. 95% of pts received prior doxorubicin, ifosfamide or both, 7 patients had 2 prior lines. Grade III monophasic pattern was seen in 21 patients, grade II in 13. 171 cycles were delivered, median number of cycles was 4 (2-10). The objective responses were CR 0; PR 15; SD 14; PD 2; and NE 3, resulting in an ORR of 44%. The clinical benefit rate was 85%. Median PFS: 11.6 months (95% CI: 9-14). Eleven pts were amenable to a subsequent resection of residual disease. Common adverse events included grade III/IV neutropenia: 47%, febrile neutropenia: 12%, thrombocytopenia: 12%, cystitis: 3%, neurologic: 3%. There was no treatment related death. Conclusions: HDI demonstrated clinically meaningful efficacy with manageable toxicity in pts who failed previous standard Ifosfamide dose. Ifosfamide remains the most active agents in SS and high dose regimen have to be considered in pts previously treated with ifosfamide.

Pharmacotherapy of sarcoma

Background: Comprising < 1% of adult malignancies and approximately 12% of pediatric malignancies, sarcomas are derived from a variety of connective tissues and exhibit highly variable responsiveness to therapy. The clinical and biologic heterogeneity of the > 50 histologic subtypes of sarcomas often require different therapeutic approaches. Objective: This review describes the use of therapeutic agents in the management of bone and soft-tissue sarcomas. Methods: Relevant literature is identified and presented from major conference proceedings, as well as using the PubMed search engine. Results/conclusions: Chemotherapy has improved outcomes over the past few decade, particularly in patients with certain bone sarcomas and gastrointestinal stromal tumors; while in the majority of patients, additional strategies are necessary.

Sarcomas and Pharmacogenetics

Sarcomas are a heterogeneous group of tumors, requiring different chemotherapeutic approaches. Recently, several regimens for metastatic tumors were evaluated with respect to the different responses to conventional chemotherapy of the various histologic subtypes of sarcomas. The impact of pharmacogenetics in the progress of chemotherapy appears to be crucial in defining the clinical response to many drugs, such as anthracycline or alkylating agents, that are widely used in treatment regimens for soft tissue sarcomas (STS) or sarcomas of the bone. Polymorphisms of metabolizing enzymes (e.g., cytochrome P450 and glutathione-S-transferase), transporter proteins (reduced folate carrier and P-glycoprotein) or target proteins (thymidylate synthase, methylenetetrahydrofolate reductase, dihydrofolate reductase, and c-KIT) may be responsible for an altered clinical outcome, in terms of both response and toxicity. The administration of new chemotherapeutic agents, such as imatinib for gastrointestinal tumors (GIST), requires the study of genetic polymorphisms possibly affecting the integrity of the target (c-KIT), which may provide valid information regarding possible developments of therapy. For STS and sarcoma of the bone, the genetic markers, which could be unambiguously predictive of the phenotypic profile of patients, are as yet undetermined.

Genetic predictors for drug resistance in soft tissue sarcoma: a review of publications in 2004

Sarcomas are generally managed through a multidisciplinary approach including surgery, radiotherapy, and chemotherapy. Metastatic tumor cells frequently develop resistance to cytotoxic agents. Several molecular mechanisms of drug resistance have been uncovered recently. Among genes governing the apoptosis pathway, overexpression of the bcl2 family or mutations of p53 have recently been reported to be involved in drug resistance in sarcoma. The multidrug resistance genes are involved in the efflux of chemotherapeutic agents. Identification of members of this family of genes may predict resistance for developing new strategies. Several histologic subtypes of sarcomas have specific mechanisms of resistance. Methotrexate is one of the four active drugs for osteosarcoma and penetrates in tumor cell through specific carrier (reduced folate carrier) whose levels of expression or changes in amino acid sequence correlate to resistance to methotrexate. Specific molecular alteration defining nosological entities among sarcoma also correlates to drug resistance. Thirty percent of human sarcomas are characterized by specific translocations that may predict, for specific subtypes, survival and response to treatment. Finally, gastrointestinal tumors harbor specific activating mutations in KIT or PDGFRA genes, which are responsive to imatinib. Specific mutations of the KIT and PDGFRA genes have now repeatedly been found correlated to response or resistance to imatinib. The molecular alterations present in tumor cells predict influence sensitivity or resistance to chemotherapy. Ultimately, this may delineate specific therapeutic strategies for both cytotoxic and targeted therapies in sarcomas.

Differential Gene Expression in Liposarcoma, Lipoma, and Adipose Tissue

Malignant transformation is thought to be associated with changes in the expression of a number of genes, and this alteration in gene expression is felt to be critical to the development of the malignant phenotype. Sarcomas represent a diverse group of tumors derived from cells of mesenchymal origin. Marked heterogeneity exists in the biological behavior of sarcomas, even within histologic subtypes of sarcomas. In an effort to better understand the biology of liposarcomas, gene expression in normal adipose tissue, lipomas, and liposarcomas was examined using the Affymetrix® microarray technology. Differences in gene expression were quantified as the fold change in gene expression among the sample sets. Differences in gene expression among normal adipose tissue, lipomas, and liposarcomas were observed. In addition, genes expressed uniquely in liposarcoma among these and 18 other tissue sample sets were identified. Gene sets were devised that allowed the separation of liposarcomas from other samples, and most normal adipose tissue from most lipomas using the Eisen clustering software “Cluster.” We conclude that differences in gene expression can be identified among different tumors derived from the adipocyte series. Such differences in gene expression may help differentiate among subtypes of sarcomas, and may also yield clues to the pathophysiology of this heterogeneous group of tumors.

SPERMATIC CORD SARCOMA: OUTCOME, PATTERNS OF FAILURE AND MANAGEMENT

We evaluate the outcome, clarify the patterns of failure and suggest treatment strategies for sarcoma in the spermatic cord. Between 1956 and 1998, 32 patients with spermatic cord sarcoma were treated at M. D. Anderson Cancer Center. A retrospective review of disease outcome, patterns of relapse and patient survival was performed. Histological subtypes of sarcoma were malignant fibrous histiocytoma in 12 patients, leiomyosarcoma in 6, liposarcoma in 8 and other subtypes in 6. All except 2 patients underwent radical orchiectomy with or without additional resection to achieve negative margins. Margins were microscopically negative in 29 cases and positive in 3. There were 3 patients who received adjuvant radiation to the surgical site. With a median followup of 9 years the 10 and 15-year actuarial local control, distant metastasis-free and overall survival rates were 72% and 61%, 85% and 85%, and 63% and 52%, respectively. The major pattern of failure was local recurrence that occurred in 8 of the 12 patients in whom disease relapsed and was the sole site of relapse in 7. Pelvic nodes had relapsed in 2 patients and para-aortic nodes in 1. Hematogenous metastases had developed in 4 patients. Of the 7 cases of disease that recurred locally only 3 were salvaged. No relapse occurred in the 3 patients treated with combined surgery and radiation. Spermatic cord sarcoma has a high propensity for local recurrence after surgery. Nodal relapse is less frequent than commonly believed. Because of the relatively high local failure rate seen in surgery alone and durable local control noted in 3 patients treated with surgery plus radiotherapy, combined modality treatment should be considered in those with spermatic cord sarcoma who are believed to be at high risk for local failure.

Bone Metastases from Soft Tissue Sarcomas.

The incidence, distribution, time of appearance, and radiologic findings of bone metastases from soft tissue sarcomas, exclusive of lymphomas, were evaluated in 320 patients with soft tissue sarcomas. Thirty patients (9.4%) had evidence of 58 bone metastases. Five of 30 patients presented with metastases, and 25 of 30 patients developed metastases up to 66 months after presentation with a mean time interval of 21.3 months. The incidence of skeletal metastases differed among histologic subtypes of sarcomas; alveolar soft part sarcoma (5 of 8), dedifferentiated liposarcoma (2 of 4), angiosarcoma (2 of 4), and rhabdomyosarcoma (5 of 16) tended to show a higher incidence of bone metastases. The sarcomas metastasized to the regional bones close to the primary tumor in 16 (53%) of 30 patients and to the axial bones in 18 (60%). On conventional radiographs, the osseous metastases demonstrated predominantly osteolytic changes, and evidence of pathological fracture was observed in 31% of 58 metastases.

Skeletal metastases from soft-tissue sarcomas

We reviewed 277 patients with soft-tissue sarcoma (STS) treated between 1975 and 1995 to study the incidence, distribution, time of appearance, and radiological findings of skeletal metastases. Of these, 28 (10.1%) had metastases within a mean period of 18.6 months after admission. The incidence of skeletal metastases differed among the histological subtypes of sarcoma; alveolar soft-part sarcoma, dedifferentiated liposarcoma, angiosarcoma, and rhabdomyosarcoma tended to show higher incidences. The regional bones close to the primary tumour were affected in 13 (46.4%) of the 28 patients, and the axial bones in 18 (64.3%). Radiologically, the metastatic bony lesions predominantly showed osteolytic changes, and there were pathological fractures in 21 of 44 lesions.

SKELETAL METASTASES FROM SOFT-TISSUE SARCOMAS

We reviewed 277 patients with soft-tissue sarcoma (STS) treated between 1975 and 1995 to study the incidence, distribution, time of appearance, and radiological findings of skeletal metastases. Of these, 28 (10.1%) had metastases within a mean period of 18.6 months after admission. The incidence of skeletal metastases differed among the histological subtypes of sarcoma; alveolar soft-part sarcoma, dedifferentiated liposarcoma, angiosarcoma, and rhabdomyosarcoma tended to show higher incidences. The regional bones close to the primary tumour were affected in 13 (46.4%) of the 28 patients, and the axial bones in 18 (64.3%). Radiologically, the metastatic bony lesions predominantly showed osteolytic changes, and there were pathological fractures in 21 of 44 lesions.

Cytogenetic findings in 73 osteosarcoma specimens and a review of the literature

Tumor-specific chromosomal abnormalities have been identified in several histologic subtypes of sarcomas. Characterization of recurrent chromosomal abnormalities has provided direction for molecular investigations of pathogenetically important genes. Cytogenetic reports of osteosarcoma, the most common primary malignant bone tumor, are relatively rare. In this study, 73 osteosarcoma specimens from 51 patients were cytogenetically analyzed following short-term culture. Clonal chromosomal abnormalities were detected in 47 and included one haploid specimen, 18 near-diploid specimens, 17 near-triploid, 8 near-tetraploid, 1 near-hexaploid, and 2 specimens with multiple clones of different ploidy levels. Examination of the present data and previously published data (111 clonally abnormal osteosarcoma specimens) reveals that chromosomal bands or regions 1p11-13, 1q10-12, 1q21-22, 11p15, 12p13,17p12-13, 19813, and 22ql1-13 are most frequently rearranged and the most common numerical abnormalities are +1, −9, −10, −13, and −17. Partial or complete loss of the long arm of chromosome 6 also was seen in all cases of the present study and all previously published cases describing structural abnormalities of 6q. Parosteal osteosarcoma, a prognostically favorable osteosarcoma subtype, was characterized by the presence of a ring chromosome accompanied by no or few other abnormalities. Complex karyotypes were seen nearly exclusively in the high-grade lesions. These findings indicate that specific chromosomal bands and/or regions are nonrandomly involved in osteosarcoma and may provide useful clinical information.

MDM2 gene amplification and transcript levels in human sarcomas: relationship to TP53 gene status.

Alterations of the TP53 tumor suppressor gene appear to be implicated in the tumorigenesis and progression of several types of human cancer, including different histologic subtypes of sarcomas. The MDM2 (murine double minute-2) gene encodes a nuclear phosphoprotein that may interact with both mutant and wild-type p53 proteins, thereby inhibiting p53-mediated transactivation in a dose-dependent manner. Recently it has been suggested that mdm2 and p53 proteins are components of an autoregulatory loop in which the MDM2 gene is transactivated by p53. Our purpose was to examine the frequency of MDM2 amplifications in larger panels of sarcomas, determine if the mRNA level could be elevated in tumors without concomitant gene amplification, and relate MDM2 findings to the TP53 status of the tumors. Sarcoma tissue of different histologic subtypes was obtained from 68 patients at the time of surgery and from 26 human xenografts in nude mice. In addition, two human sarcoma cell lines (OSA and U2OS) were studied. Genomic DNA from tumor tissue, in vitro cell lines, and peripheral blood cells were isolated by Southern-blot analysis methods to determine MDM2 gene amplification. Tumor DNA was analyzed for possible TP53 gene mutations in exons 5, 7, and 8 by constant denaturing gel electrophoresis. To determine the MDM2 and TP53 mRNA levels, Northern-blot analysis was performed. Amplification of the MDM2 gene was detected in 10 tumors (10.3%). Whereas MDM2 amplification and/or over-expression were found only in two (U2OS and OSA cell lines) of 18 osteosarcomas, one of 20 malignant fibrous histiocytomas (MFHs), and in none of 14 leiomyosarcomas, such alterations were observed in two of two fibrosarcomas, three of six malignant schwannomas, three of 19 liposarcomas, and in the one hemangiopericytoma examined. MDM2 overexpression was found in all nine examined cases with and in three tumors without amplification. TP53 mutations were detected in 12 cases (five osteosarcomas, four MFHs, and three leiomyosarcomas), of which none showed amplification, but one had increased levels of MDM2 mRNA. None of the fibrosarcomas, malignant schwannomas, and liposarcomas examined had mutated TP53. The six sarcomas that showed high TP53 mRNA expression in the absence of gene mutation also had elevated levels of MDM2 mRNA. The present data provide further indications that increased MDM2 expression level, caused by gene amplification or altered regulation of transcription, is involved in tumor progression of some, but not all, sarcoma subtypes.

Chromosome analysis of nine osteosarcomas.

Although recurrent chromosome abnormalities have been identified in several histologic subtypes of sarcomas, no consistent rearrangement has yet been found in osteosarcomas. Cytogenetic analyses of nine cases of osteosarcoma are reported, including seven newly diagnosed tumors and two recurrent tumors. There were seven high-grade osteosarcomas, one periosteal osteosarcoma, and one well-differentiated sarcoma. All tumors were studied in short-term primary culture. Modal number ranged from near diploid to near triploid. Seven tumors had complex karyotypes with multiple structural abnormalities; two had only normal karyotypes. The retinoblastoma gene on chromosome 13 and the TP53 gene on chromosome 17 have been involved in osteosarcoma. Five tumors had loss of a whole copy of chromosome 13, and three of these also had a loss of a whole copy of chromosome 17. However, these losses were observed in the setting of numerous other chromosome losses. Numerous structural abnormalities were observed, many involving additions of unidentified material, unbalanced translocations, or deletions. Structural abnormalities with similar breakpoints involving 6q, 8q, 9q, and 14p were seen in two or three tumors each. When the tumors in this series were added to the 18 published cases, the pericentromeric regions of chromosomes 1, 3, and 14, and segments 6q15-21, 8q24, 9q34, 12p13, 17p13, and 19q13, were found to be involved in five or more structural rearrangements. Molecular analyses of these chromosome regions may yield genes important in the pathogenesis of osteosarcoma.