Classification of rhabdomyosarcomas and related sarcomas. Pathologic aspects and proposal for a new classification--an Intergroup Rhabdomyosarcoma Study

Treatment of non-metastatic rhabdomyosarcomas in childhood and adolescence. Results of the second study of the International Society of Paediatric Oncology: MMT84

The second International Society of Paediatric Oncology (SIOP) study for rhabdomyosarcoma (MMT84) had several goals. The two principal aims were: (1) to improve the survival of children with rhabdomyosarcoma; and (2) to reduce the late effects from therapy by restricting the indications for surgery and/or radiotherapy after good response to initial chemotherapy. A further aim was to investigate the role of high-dose chemotherapy in young patients with parameningeal primary tumours. 186 previously untreated eligible patients entered the study. Patients with completely resected primary tumour received three courses of IVA (ifosfamide, vincristine and actinomycin D). Patients with incompletely resected tumour received six to 10 courses of IVA according to stage. Patients achieving complete remission with chemotherapy alone did not usually receive radiotherapy or undergo extensive surgery, but patients remaining in partial remission received local therapy with surgery and/or radiotherapy. Only patients over 5 years of age with parameningeal disease and patients over 12 years with tumours at any site were given systematic irradiation. Complete remission was achieved in 91% (170/186) of all patients. With a median follow-up of 8 years, the 5-year overall survival was 68% (+/- 3% standard error of the mean (SEM) and the 5-year event-free survival 53% (+/- 4% SEM). These results show an improvement over previous SIOP study (RMS75) in which survival was 52% and event-free survival was 47%. Among the 54 patients who exhibited isolated local relapse, 35% (19/54) survived in further remission longer than 2 years after retreatment, including local therapy (surgery +/- radiotherapy). Analysis of the overall burden of therapy received by all surviving children (including primary treatment and treatment for relapse if required) showed that 24% (28/116) were treated by limited surgery followed by three courses of IVA, 29% (34/116) were treated by chemotherapy alone (after initial biopsy) and 13% (15/116) received chemotherapy plus conservative local treatment (limited surgery or radiotherapy for residual disease). Only 34% (39/116) received intensive local therapy defined as radical wide field radiotherapy or radical surgery or both. Compared with the results obtained in the previous SIOP study, treatment in MMT84 was based on response to initial chemotherapy and, despite an overall reduction of the use of local therapy, significantly improved survival for patients with non-metastatic disease. This trial, also for the first time, provides evidence that retreatment after local relapse can achieve long-term second remissions.

Loss of heterozygosity on the long arm of chromosome 11 in orbital embryonal rhabdomyosarcoma (OERMS): a microsatellite study of seven cases

OBJECTIVES. To investigate, by means of microsatellite analysis, regions of chromosome 11 involved in the genesis of embryonal rhabdomyosarcoma (ERMS) localized to the orbit. METHODS. Microsatellite analysis was carried out on seven cases of orbital ERMS by comparing the electrophoretic migration patterns of PCR-amplified microsatellites of chromosome 11 from both constitutional (blood) and tumor genotypes. Five of the tumors analyzed were samples frozen at the time of surgery, and two were paraffin embedded. RESULTS. Overall, microsatellites D11S1396 (11q13.1-q22.3) and D11S976 (11q) showed loss of heterozygosity (LOH) in all tumor samples, thus indicating the presence, on the long arm of chromosome 11, of one or more tumor suppressor genes with a possible role in the genesis of the disease. CONCLUSION. While the role of genes on the short arm of chromosome 11 in the genesis of ERMS is well established, much less is known of the possible involvement of tumor suppressor genes on the long arm of the same chromosome. This is the first report showing the possible involvement of tumor suppressor genes in this portion of the chromosome in ERMS localized to the orbit.

Polymerase chain reaction-based diagnosis of rhabdomyosarcomas: comparison of fetal type acetylcholine receptor subunits and myogenin

The diagnosis of rhabdomyosarcoma (RMS) is usually straight-forward when light microscopy and immunohistochemistry are used. However, tumors that exhibit a low degree of differentiation and small biopsies can lead to confusion. In such patients and for the detection of minimal (residual) disease, a polymerase chain reaction (PCR)-based approach would be a valuable diagnostic adjunct. This type of approach would be highly sensitive and should be free from the risk for contamination of the tumor sample with normal tissue. Because myogenin and the alpha and gamma subunit of the fetal type acetylcholine receptor (AChR) are specific immunohistochemical markers for RMS, their expression on the mRNA level in RMS, other childhood and adult tumors, and normal tissues was studied. Although the sensitivity of both approaches was 100% in embryonal and alveolar RMS, detection of myogenin mRNA was not specific for RMS but occurred in normal muscle and the majority of the other normal tissues and childhood tumors. Conversely, detection of fetal AChR mRNA as defined by an alpha/tau ratio of < 1 was encountered only in RMS and denervated muscle. The authors conclude that mRNA of the fetal type AChR but not myogenin is a highly specific and sensitive target for the PCR-based diagnosis of RMS.

Characterization of a new human embryonal rhabdomyosarcoma cell line, RMS-GR

A human tumor cell line designated RMS-GR was established from an embryonal rhabdomyosarcoma. The monolayer cells were polygonal, round or spindle-shaped. The RMS-GR cell line became stable with a doubling time of 42 h. Tumorigenicity of the cells was confirmed by heterotransplantion into nude mice. Electron microscopic images showed typical cytoplasmic inclusion of aggregated intermediate filaments and myofibril-like thin filaments. The expression of desmin, vimentin, actin and human myoglobin was recognized by cytofluorometric analyses, and a large fraction of CK-MM and small fractions of CK-BB and MCK-1 isoenzymes were found. Chromosomal analysis showed that the modal chromosome number was consistently near triploid with structural abnormalities mostly involving chromosomes 1, 3 and 8, and additional unidentified markers. No alteration of chromosome 2 was observed. The RMS-GR cell line may provide a system to identify genes which are involved in the pathogenic mechanism of rhabdomyosarcomas, and to investigate the modulation of myogenic differentiation.

Spindle cell rhabdomyosarcoma (so-called) in adults: report of two cases with emphasis on differential diagnosis

Spindle cell rhabdomyosarcoma (RMS) is a recently described variant of embryonal RMS that carries a relatively favorable prognosis when compared with other forms of RMS. To date, spindle cell RMS has been described only in children. The authors have identified two unusual cases occurring in adults using the following criteria: tumors composed mainly of fascicular, relatively monomorphic spindle-shaped cells that show unequivocal immunohistochemical and ultrastructural evidence of myogenic differentiation. The tumors were identified in a 38-year-old woman and a 56-year-old man, arising in the cheek and left hemidiaphragm, respectively. Both were treated with surgical resection and chemotherapy. The first patient died of uncontrolled local recurrence of her tumor at 27 months after diagnosis, and the second died of metastatic disease at 13 months follow-up. The tumors were composed mainly of fascicles of spindle cells with palely eosinophilic cytoplasm admixed diffusely with sparse polygonal, rounded, or strap-shaped rhabdomyoblasts with brightly eosinophilic cytoplasm and with cross-striations in the first case only. Immunostaining for muscle-related antigens showed staining for smooth-muscle actin (focal), pan-actin HHF-35, desmin, fast myosin, myoglobin, and MyoD1. Both cases were negative for S-100 protein. On electron microscopy, both cases showed neoplastic rhabdomyoblasts with clear-cut sarcomeric differentiation in many of the tumor cells. Spindle cell RMS poses special problems in differential diagnosis when arising in adults and should be distinguished from leiomyosarcoma, malignant peripheral nerve sheath tumor with heterologous rhabdomyoblastic differentiation (malignant Triton tumor), and fibrosarcoma. In view of the good prognosis afforded children with spindle cell RMS and in light of the chemoresponsive behavior of RMS in general, we feel that it is important to identify tumors that meet the criteria for spindle cell RMS occurring in the adult population. However, based on these two cases, it is possible that spindle cell RMS occurring in adults may not be associated with such a favorable outcome.

Undifferentiated sarcomas of children: pathology and clinical behavior--an Intergroup Rhabdomyosarcoma study

Undifferentiated soft tissue sarcoma (UND-STS) is the most poorly defined tumor eligible for intergroup Rhabdomyosarcoma Studies (IRS). Recent IRS UND-STS experience was reviewed to assess the histologic characteristics and clinical behavior of undifferentiated sarcomas. Of the 1,527 patients entered on IRS-III and IRS pilot-IV, 96 had tumors classified by the IRS Pathology Committee as UND-STS. Of these, 52 had adequate histologic material for this study. After application of immunohistochemistry, 18 tumors were reclassified, mostly as embryonal rhabdomyosarcomas (RMS), primitive neuroectodermal tumors, and intraabdominal desmoplastic small found cell tumors. The remaining 34 UND-STS had a diffuse hypercellular histologic pattern made up of sheets of medium-sized cells. The tumor cells had a minimal to moderate amount of cytoplasm and a variable nuclear morphology, predominately vesicular with finely granular chromatin. Except for reactivity with antibodies against vimentin, most tumors had a negative immunohistochemical profile. The 5 year Kaplan-Meier survival estimate for patients with non-metastatic disease was 72%, a significant improvement when contrasted with patients diagnosed to have UND-STS in IRS-I and IRS-II.

Rhabdomyosarcoma. Biology and treatment

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Recognition of specific genetic changes in the two most common subtypes of rhabdomyosarcoma has allowed better understanding of the pathogenesis of this disease. In addition, identification of prognostic factors and the use of risk-directed multimodal therapy have improved the outcome for these patients significantly, with cure rates approaching 70%.

Phosphotyrosyl proteins in childhood rhabdomyosarcomas: phosphorylation of catenins and components of the insulin-like growth factor type I receptor signaling cascade

PURPOSE

Rhabdomyosarcomas (RMS) are heterogeneous in their clinical presentation, histology, and cytogenetics. The growth of some RMS cells has been found to be regulated by the tyrosine kinase insulin-like growth factor (IGF) type I receptor. However, RMS cells exhibit variable sensitivity to inhibitors of tyrosine kinases and IGF receptors. Collectively, these heterogeneous features suggest that differences exist in the growth regulatory pathways of RMS. The objective of this study is to identify active tyrosine kinase signal transduction pathways in embryonal and alveolar RMS cells.

METHODS

RMS tumor samples and cell lines representing both embryonal and alveolar histologic subtypes have been analyzed by immunoprecipitation and immunoblotting techniques to characterize phosphotyrosyl protein patterns and to identify tyrosine phosphorylated proteins.

RESULTS

RMS cells can be characterized based on the patterns of phosphotyrosyl proteins, including the phosphorylation status of the catenin-like protein Cas1 and the signal adapter protein SHC, and the activation of IGF type I receptor signaling cascades including the formation of SHC-GRB2 signal protein complexes and MAP kinase activation.

CONCLUSIONS

Rhabdomyosarcomas, especially the embryonal histologic subtype, are heterogeneous at the level of tyrosine kinase signal transduction. It will be important to characterize the growth regulatory pathways active in individual RMS tumors before targeting molecular therapies to this malignancy.

Orbital rhabdomyosarcomas and related tumors in childhood: relationship of morphology to prognosis--an Intergroup Rhabdomyosarcoma study

Children and adolescents who develop rhabdomyosarcoma (RMS) and related sarcomas in the orbit and treated on Intergroup Rhabdomyosarcoma protocols have had an extremely high cure rate. This study evaluates the possible relationship between their tumor morphologic subtypes and this high cure rate. The histology of tumors was re-reviewed from 229 of the 264 patients with tumors of the orbit, conjunctiva, and eyelids treated on Intergroup Rhabdomyosarcoma Studies (IRS I, II, III, and IV pilot protocols, and followed through July, 1992. Immunohistochemistry was applied in selected cases. Clinical correlations were done on all 264 cases including both the re-reviewed cases and those reviewed only by the IRS Pathology committee. The 5-year survival rate of 24 children with alveolar RMS was 74% (p < .001). All five infants diagnosed to have an alveolar RMS died before the age of one. Two hundred and twenty-one patients (84%) had embryonal RMS. About three-fourths of the re-reviewed embryonal RMS tumors showed only minimal rhabdomyoblastic differentiation. Thirty-one had a spindle cell RMS, two were anaplastic variants. The 5-year survival rate for patients with embryonal RMS subtypes combined was 94%, and 97% for the 144 patients with poorly differentiated embryonal RMS. In contrast, 90 of 432 IRS II patients treated for poorly differentiated embryonal RMS located in extraocular sites had a 66% survival estimate.

Selection of probes for fluorescence in situ hybridization analysis by differential display polymerase chain reaction of mRNA from rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a malignancy of skeletal muscle derivation encompassing two major subtypes, embryonal and alveolar, which differ in clinical behavior and genetic markers. Because RMS is a relatively circumscribed tumor system for which the beginnings of a molecular genetic framework are in place, it becomes an ideal model for the application of improved methods of molecular genetic analysis. We have applied the technique known as differential display polymerase chain reaction (DD-PCR) to characterize expression of RNA in rhabdomyosarcoma subtypes. Our studies have shown that DD-PCR generates a characteristic electrophoretic profile that can be used to isolate subtype specific probes for fluorescence in situ hybridization (FISH) analysis. We have isolated two cDNA fragments and obtained clones suitable for FISH mapping to metaphase chromosomes. One probe was mapped to the centromeric region of human chromosome 22 and the other probe to the human chromosome band 6q25-26. This approach demonstrates the utility of DD-PCR as a technique for isolating novel cDNA expressed in tumors and their subsequent use as probes for FISH analysis. As more genes are identified by DD-PCR and their roles in tumorigenesis become defined, they are likely to provide novel targets for future molecular cytogenetic analysis.

The diagnostic potential of the chromosome translocation t(2;13) in rhabdomyosarcoma: a Pcr study of fresh-frozen and paraffin-embedded tumour samples

The chromosomal translocation t(2;13)(q35;q14) has been reported in alveolar paediatric rhabdomyosarcoma. The rearrangement leads to the juxtaposition of the PAX-3 and FORKHEAD genes and the production of a fusion protein with putative transcriptional regulatory activity. The diagnostic potential of this translocation has been examined using a reverse transcription polymerase chain reaction (RT-PCR) assay to detect translocations in both fresh-frozen and archival formalin-fixed, paraffin-embedded rhabdomyosarcoma. A total of 25 tumours and one cell line were examined. PAX-3-FORKHEAD chimeric mRNAs were amplified by PCR in 8 of 15 cases of alveolar rhabdomyosarcoma. Translocations were detectable in both fresh-frozen tissues (4 of 7) and paraffin-embedded tumours (3 of 7) and in the alveolar rhabdomyosarcoma cell line. Our study confirms that the t(2;13) translocation is not present in embryonal rhabdomyosarcomas, but can be detected in nearly half of alveolar rhabdomyosarcomas, whether fresh-frozen or paraffin-embedded. The PCR-based t(2;13) translocation assay can aid in the diagnosis of rhabdomyosarcoma, but cannot replace a careful histopathological evaluation. It may contribute in further characterizing an otherwise undifferentiated small cell tumour, where it may be indicative of clinical behaviour.