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

Immunohistochemical expression and cluster analysis of mesenchymal and neural stem cell-associated proteins in pediatric soft tissue sarcomas

Pediatric undifferentiated soft tissue sarcomas (USTSs) are a group of malignancies composed predominantly of primitive round cell sarcomas, the histogenesis of which is uncertain. Thus, diagnosis and therapy remain a challenge. The aims of the current study were to determine whether differential expression of stem cell-associated proteins could be used to aid in determining the histogenesis of pediatric USTSs and to determine whether pediatric USTSs expressed a unique panel of stem cell-associated proteins to aid diagnosis. Tumors included 28 Ewing sarcoma/primitive neuroectodermal tumors (ESs), 22 embryonal rhabdomyosarcomas (ERMSs), 8 alveolar rhabdomyosarcomas (ARMSs), 5 synovial sarcomas (SSs), 5 malignant peripheral nerve sheath tumors (MPNSTs), and 13 USTSs. Stem cell antibodies included 3 mesenchymal stem cell markers (CD44, CD105, and CD166) and 5 neural stem cell markers (CD15, CD29, CD56, CD133, and nestin). Sections were scored followed by statistical analysis, clustering analysis, and visualizations using Partek Genomic Suite Software. The Euclidean clustering divided the tumors into 2 major groups. ESs and USTSs formed the majority of the 1st group, whereas ERMSs, ARMSs, MPNSTs, and SSs formed the 2nd group. Reduced expression of CD56 was strongly associated with the ES/USTS cluster (P < 0.0001). ESs and USTSs were further separated by CD166 staining, wherein increased expression was associated with ES (P < 0.0001). The 2nd group included the majority of other sarcomas, with no consistent separation between subtypes. The current study demonstrates the usefulness of applying stem cell markers to pediatric sarcomas and indicates that USTSs and ESs are closely related and may share a common histogenesis.

Selecting multimodal therapy for rhabdomyosarcoma

Rhabdomyosarcoma is a typical tumor of childhood, characterized by a high grade of malignancy, local invasiveness and a marked propensity to metastasize, but also a generally good response to chemotherapy and radiotherapy. Multimodal therapy is essential to cure rhabdomyosarcoma patients, but different uses of surgery, radiotherapy and chemotherapy, and their intensity, need to be selected and modulated to different patient risk groups. This article attempts to give an account of the current treatment options, the open and debated issues and the potential novel strategies for the near future.

Optimising the management of soft tissue tumours

The Royal College of Pathologists of Australasia is developing a series of protocols as an educational tool to assist pathologists in the reporting of relevant information for specific cancer specimens. The protocol for the management of soft tissue tumour resections has recently been released, and this document elaborates the relevant literature on which that protocol drew. Sarcoma is uncommon but is associated with significant morbidity and mortality, and its management is complex. Diagnostic errors are not uncommon and these can have disastrous effects on patient outcome. Sophisticated ancillary testing is often an important adjunct to diagnosis and prognostication. Referral to a specialist sarcoma unit is indicated for both adult and paediatric sarcoma.

Pediatric rhabdomyosarcoma at presentation: can cross-sectional imaging findings predict pathologic tumor subtype?

OBJECTIVE

The purpose of the study is to determine whether there are cross-sectional imaging features of pediatric rhabdomyosarcoma that are specific to the different pathologic subtypes of the tumor.

MATERIALS AND METHODS

Medical records of 14 pediatric patients who were diagnosed with rhabdomyosarcoma were reviewed retrospectively. Patient demographics, including age and sex, as well as final pathologic report were obtained. The initial CT, MRI, or both obtained at presentation, prior to the diagnosis being established, were reviewed by two radiologists. We recorded tumor features including site, size, margins, local extension, and presence of metastases. Presence of calcification, hemorrhage, or necrosis as well as attenuation and heterogeneity of the tumor were also recorded.

RESULTS

Ten of our fourteen patients were formally diagnosed with the embryonal subtype of rhabdomyosarcoma, while three were found to have the alveolar subtype, and one subtype was poorly differentiated. There was no significant difference in the attenuation and in the heterogeneity of the tumor between the embryonal and the alveolar subtype on CT.

CONCLUSION

Imaging features at presentation, such as attenuation and heterogeneity, could not correlate to the pathologic subtype of pediatric rhabdomyosarcoma.

Hedgehog signal inhibitor forskolin suppresses cell proliferation and tumor growth of human rhabdomyosarcoma xenograft

BACKGROUND/PURPOSE

We have previously reported that the Hedgehog (Hh) signaling pathway is activated in pediatric malignancies. In this study, we examined the effect of the Hh signal inhibitor forskolin on the growth of rhabdomyosarcoma (RMS) in vivo and in vitro and thereby elucidated the possibility of considering Hh signaling pathway as a therapeutic target for RMS.

METHODS

We evaluated the messenger RNA expressions of Hh signal mediators in 3 human RMS cell lines using reverse transcriptase-polymerase chain reaction method. The effect of forskolin on the tumor cell proliferation was investigated using WST-1 assay (Dojindo Co, Kumamoto, Japan). We inoculated 10(7) tumor cells into the back of nude mice to create RMS xenograft tumor models. Forskolin was subcutaneously administered in the region around the tumor, and the effect on the tumor growth was evaluated.

RESULTS

The messenger RNA expression of glioma-associated oncogene homolog 1, the marker of Hh signaling activation, was expressed at various levels in RMS cell lines. The proliferation of RMS cells was inhibited in a dose-dependent fashion by forskolin. Similarly, in the xenograft model, tumor growth was also significantly reduced by forskolin treatment.

CONCLUSIONS

Our findings suggest that the Hh signaling pathway plays an important role in the tumorigenesis of RMS and that this pathway can be considered to be a potential molecular target of new treatment strategies for RMS.

Establishment and characterization of the rhabdomyosarcoma cell line designated NUTOS derived from the human tongue sarcoma: Special reference to the susceptibility of anti-cancer drugs

Primary alveolar type of rhabdomyosarcoma (RMS) tumor tissue was collected from the tongue of a 17-year-old Japanese woman and used to successfully establish a rhabdomyosarcoma cell line, which has been designated NUTOS. The chromosomal distribution revealed that the NUTOS cell line was hyper-tetraploid with chromosomal translocation. The cells were grown in Dulbecco's modified eagle medium/F12 supplemented with 15% fetal bovine serum, 0.1% non-essential amino acids solution (NEAA), 50 microg of streptomycin, 50 U/mL of penicillin and 0.25 microg /mL of Fungizone. The NUTOS shapes included small spindles, large spindles and long, thick multinucleated cells. All three cell types were immunostained with anti-desmin antibody, which is a marker protein for middle sized myofilaments. Furthermore, immunocytochemical staining revealed that the cells were positively immunostained with anti-MyoD, myogenin, alpha-sarcomeric actin, myosin and troponin T. Mitotic figures were only observed in the small spindle cells. These cells were coadunated with each other at the lateral portion of the apex of the cells. Subsequently, these cells grew into large multinucleated cells. Autonomic contractions (approximately 20 times/min) were observed in both the large spindle cells and the large multinucleated cells. NUTOS cells incorporated serotonin from the serum in the growth medium. Histopathological observations of the NUTOS cell grafts in the subcutis of nude mice exhibited characteristics similar to those seen for the primary rhabdomyosarcoma of the tongue. Susceptibility tests for the anti-cancer drugs revealed that NUTOS cells were susceptive to cisplatin, paclitaxel, and docetaxel, but not to adriacin.

Treatment results for patients with localized, completely resected (Group I) alveolar rhabdomyosarcoma on Intergroup Rhabdomyosarcoma Study Group (IRSG) protocols III and IV, 1984-1997: a report from the Children's Oncology Group

PURPOSE

To assess local control, event-free survival (EFS), and overall survival (OS) rates in 71 patients with localized, completely resected (Group I) alveolar rhabdomyosarcoma (ALV RMS) and their relation to radiation therapy (RT) on IRSG Protocols III and IV, 1984-1997.

METHODS

Chart review and standard statistical procedures. PATIENTS AND TUMORS: Patients were 1-18 years at diagnosis (median, 6 years). Primary tumor sites were extremity/trunk (N = 54), head/neck (N = 9), genitourinary tract (N = 7), and perineum (N = 1). Thirty patients received VA +/- C with RT; 41 received VA +/- C alone. RT was assigned, not randomized.

RESULTS

Fifty-four patients had Stage 1 (favorable site, any size) or Stage 2 (unfavorable site, < or = 5 cm) tumors. Eight-year EFS was 90%, with 100% local control for 17 patients given RT. Eight-year EFS was 88%, with 92% local control for 37 patients without RT; P = 0.52 for EFS comparisons, 0.3 for local control comparisons. In 17 Stage 3 patients (unfavorable site, tumors >5 cm, N0), 8-year EFS was 84% with 100% local control in 13 patients given RT; 8-year EFS was only 25% and local control 50% in 4 patients without RT. Local recurrence was the most common site of first failure in non-irradiated patients.

CONCLUSION

Patients with Stage 1-2 ALV RMS had slightly but statistically insignificantly improved local control, EFS, and OS rates when local RT was given. The need for local RT in Stage 1-2 patients deserves evaluation in a randomized study. Local control, EFS, and OS rates were significantly improved in Stage 3 patients receiving local RT.

Modern Diagnosis of Small Cell Malignancies of Children

Small cell malignancies of children constitute a continuing diagnostic challenge for surgical pathologists, although modern methods of ancillary diagnosis provide powerful tools that resolve most difficult cases. Current techniques range from identification of DNA alternations, including gene fusions, chromosome translocations, and genetic deletions, to recognition of characteristic patterns of protein expression, usually visualized with immunohistochemistry. In spite of these advances, recognition of key cellular and histologic features remains the keystone of diagnosis but requires adequately fixed and carefully stained histologic sections. Cytologic features now suffice for diagnosis if confirmed by appropriate testing. This article outlines key histologic features of pediatric small cell neoplasms and the algorithms that allow diagnostic confirmation and the initiation of appropriate therapy.

[Spindle cell rhabdomyosarcoma in adults: a new entity in the spectrum of malignant mesenchymal tumors of soft tissues]

Rhabdomyosarcomas (RMS) are rare soft tissue sarcomas showing a skeletal muscle differentiation. Histologically, embryonal, alveolar and pleomorphic subtypes are distinguished. RMS represent one of the most frequent sarcomas in children and adolescents, and in this age group embryonal and alveolar subtypes predominate. RMS in adults is extremely rare, and the pleomorphic subtype is most frequently seen. Spindle cell and sclerosing RMS in adults are very rare and, unlike the morphologically comparable tumors in children and adolescents, clinically aggressive neoplasms, which need to be distinguished from spindle cell malignant melanoma, spindle cell sarcomatoid carcinoma and from a number of spindle cell sarcomas of varying lines of differentiation. Spindle cell and sclerosing RMS in adults arise predominantly in the head and neck region and on the extremities, and are composed of atypical spindled cells and scattered rhabdomyoblasts. Since spindle cell RMS may contain areas of lower cellularity with abundant sclerosing stroma, and sclerosing RMS may show focal areas of increased cellularity, it is most likely that both forms represent a morphological spectrum of a single RMS variant.

Betulinic acid induces apoptosis and inhibits hedgehog signalling in rhabdomyosarcoma

Background:

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in childhood with the ability to resist apoptosis by the activation of survival promoting and anti-apoptotic proteins.

Methods:

Efficacy of the apoptosis-inducing agent betulinic acid (BA) was determined in RMS cell cultures and in vivo by measuring cell viability, survival, apoptosis, hedgehog signalling activity, and neovascularisation.

Results:

Betulinic acid had a strong cytotoxic effect on RMS cells in a dose-dependent manner. The BA treatment caused a massive induction of apoptosis mediated by the intrinsic mitochondrial pathway, which could be inhibited by the broad-range caspase inhibitor zVAD.fmk. Exposure of hedgehog-activated RMS-13 cells to BA resulted in a strong decrease in GLI1, GLI2, PTCH1, and IGF2 expression as well as hedgehog-responsive luciferase activity. Intraperitoneal injection of 20 mg BA per kg per day significantly retarded growth of RMS-13 xenografts in association with markedly higher counts of apoptotic cells and down-regulation of GLI1 expression compared with control tumours, while leaving microvascular density, cell proliferation, and myogenic differentiation unaffected.

Conclusion:

Our data show that induction of apoptosis and inhibition of hedgehog signalling are important features of the anti-tumourigenic effect of BA in RMS and advices this compound for the use in a multimodal therapy of this highly aggressive paediatric tumour.

Fusion gene-negative alveolar rhabdomyosarcoma is clinically and molecularly indistinguishable from embryonal rhabdomyosarcoma

PURPOSE

To determine whether the clinical and molecular biologic characteristics of the alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma (ERMS) subtypes have relevance independent of the presence or absence of the PAX/FOXO1 fusion gene.

PATIENTS AND METHODS

The fusion gene status of 210 histopathologically reviewed, clinically annotated rhabdomyosarcoma samples was determined by reverse transcriptase polymerase chain reaction. Kaplan-Meier analysis was used to assess event-free survival and overall survival in fusion gene-negative ARMS (ARMSn; n = 39), fusion gene-positive ARMS (ARMSp; n = 94), and ERMS (n = 77). A total of 101 RMS samples were also profiled for whole-genome expression, and 128 were profiled for genomic copy number imbalances. Profiling data were analyzed by supervised and unsupervised methods to compare features related to histopathology and fusion gene status. Results were also projected by meta-analysis techniques across three separate publically available data sets.

RESULTS

Overall and event-free survival, frequency of metastases, and distribution of site at initial presentation were not significantly different between ARMSn and ERMS. Consistent with this, analysis of gene expression signatures could not reproducibly distinguish ARMSn from ERMS whereas fusion gene-positive cases were distinct. ARMSn and ERMS frequently show whole-chromosome copy number changes, notably gain of chromosome 8 with associated high levels of expression of genes from this chromosome.

CONCLUSION

The clinical behavior and molecular characteristics of alveolar cases without a fusion gene are indistinguishable from embryonal cases and significantly different from fusion-positive alveolar cases. This implies that fusion gene status irrespective of histology is a critical factor in risk stratification of RMS.

A strategy to avoid facial mutilation in orbital embryonal rhabdomyosarcoma

INTRODUCTION

An orbital embryonal rhabdomyosarcoma (RMS) is a rare malignancy in children, but clinical findings are typical. We detail the case of an 8-year-old female with orbital RMS and discuss the therapeutic options.

CASE REPORT

Orbital RMS was apparent with painless exophthalmos of the right globe and diplopia. Head MRI showed tumor masses behind and inferior to the globe. Open biopsy led to the histological diagnosis. Metastasis or infiltration of orbital bone was not observed. Chemotherapy was carried out in accordance with the Cooperative Weichteilsarkom Studie (CWS) 2002 protocol. Tumor regression was detected after the first course of chemotherapy; we decided to excise the residual tumor with preservation of the globe. The CWS 2002 protocol was subsequently completed. Radiotherapy was not done. One year after treatment, RMS recurrence was not observed.

CONCLUSION

After interdisciplinary treatment, mutilation was avoided after exenteration of the orbit or radiation treatment to the growing facial skeleton. That was possible due to excision of the residual tumor in a second step, leading to down-staging of the RMS.

Surgical management of craniofacial and skull base rhabdomyosarcomas

INTRODUCTION

Craniofacial and skull base rhabdomyosarcomas (RMSs) are rare. Surgeons are involved both in the resection and the reconstruction of these tumors and in the management of late sequelae of earlier treatment. These tumors are highly heterogeneous, and the initial presentation may be insidious. We wished to determine how diagnostic difficulties could be overcome and how management outcomes could be optimized.

MATERIALS AND METHODS

All cases of RMS in patients who presented to our craniofacial program between 2004 and 2008 were retrospectively reviewed.

RESULTS

Eight consecutive patients with RMS were treated. Six patients are Maori. Four patients had surgical resections of their primary tumors including 3 with curative intent. One had a recurrent tumor, and 3 had functional reconstruction after an earlier treatment. Inaccuracies in histologic diagnosis occurred in 2 patients. Two patients developed postoperative cerebrospinal fluid leakage. Two patients had leptomeningeal involvement and died within 10 months. All patients treated with curative intent achieved complete macroscopic margins. Two remained disease-free at 10 and 22 months.

DISCUSSION

Treatment must be in the context of a multidisciplinary team with the appropriate craniofacial, neurosurgical, and reconstructive skills. Expedient and accurate histologic diagnoses by experienced pathologists are critical in optimizing the outcomes. Oncologists must be well resourced to administer chemoradiation in a timely manner. Leptomeningeal invasion is a dire prognostic feature. Cerebrospinal fluid leak after resection must be identified early and repaired. Late consequences of early childhood craniofacial cancer treatment may be ameliorated by tailored reconstructions. The predominance of Maori in our series has not been reported previously.

Molecular and cellular biology of rhabdomyosarcoma

Rhabdomyosarcoma is a group of soft-tissue sarcomas that share features of skeletal myogenesis, but show extensive heterogeneity in histology, age and site of onset, and prognosis. This review matches recent molecular data with biological features of rhabdomyosarcoma. Alterations in molecular pathways, animal models, cell of origin and potential new therapeutic targets are discussed.

Small interfering RNA library screen of human kinases and phosphatases identifies polo-like kinase 1 as a promising new target for the treatment of pediatric rhabdomyosarcomas

Rhabdomyosarcoma, consisting of alveolar (aRMS) and embryonal (eRMS) subtypes, is the most common type of sarcoma in children. Currently, there are no targeted drug therapies available for rhabdomyosarcoma. In searching for new molecular therapeutic targets, we carried out genome-wide small interfering RNA (siRNA) library screens targeting human phosphatases (n = 206) and kinases (n = 691) initially against an aRMS cell line, RH30. Sixteen phosphatases and 50 kinases were identified based on growth inhibition after 72 hours. Inhibiting polo-like kinase 1 (PLK1) had the most remarkable impact on growth inhibition (approximately 80%) and apoptosis on all three rhabdomyosarcoma cell lines tested, namely, RH30, CW9019 (aRMS), and RD (eRMS), whereas there was no effect on normal muscle cells. The loss of PLK1 expression and subsequent growth inhibition correlated with decreased p-CDC25C and Cyclin B1. Increased expression of WEE 1 was also noted. The induction of apoptosis after PLK1 silencing was confirmed by increased p-H2AX, propidium iodide uptake, and chromatin condensation, as well as caspase-3 and poly(ADP-ribose) polymerase cleavage. Pediatric Ewing's sarcoma (TC-32), neuroblastoma (IMR32 and KCNR), and glioblastoma (SF188) models were also highly sensitive to PLK1 inhibition. Finally, based on cDNA microarray analyses, PLK1 mRNA was overexpressed (>1.5 fold) in 10 of 10 rhabdomyosarcoma cell lines and in 47% and 51% of primary aRMS (17 of 36 samples) and eRMS (21 of 41 samples) tumors, respectively, compared with normal muscles. Similarly, pediatric Ewing's sarcoma, neuroblastoma, and osteosarcoma tumors expressed high PLK1. We conclude that PLK1 could be a promising therapeutic target for the treatment of a wide range of pediatric solid tumors including rhabdomyosarcoma.

Trends in childhood rhabdomyosarcoma incidence and survival in the United States, 1975-2005

BACKGROUND

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents aged<20 years; its etiology remains largely unknown. It is believed that embryonal (ERMS) and alveolar rhabdomyosarcoma (ARMS), the most common subtypes, arise through distinct biologic mechanisms. The authors of this report evaluated incidence and survival trends by RMS demographic subgroups to inform future etiologic hypotheses.

METHODS

Incidence and survival trends in RMS among children and adolescents aged<20 years were analyzed using data from the Surveillance, Epidemiology, and End Results Program. Frequencies, age-adjusted incidence and survival rates, and joinpoint regression results, including annual percentage change (APC) and 95% confidence interval (CI), were calculated.

RESULTS

Between 1975 and 2005, the incidence of ERMS was stable, whereas a significant increase in the incidence of ARMS was observed (APC, 4.20%; 95% CI, 2.60%-5.82%). This trend may have been attributable in part to shifts in diagnosis, because a significant negative trend in RMS, not otherwise specified was observed concurrently. A bimodal age peak for ERMS was observed, with the second, smaller peak in adolescence noted for males only; ARMS incidence did not vary by age or sex. Five-year survival rates for RMS and ERMS increased during the period from 1976 to 1980 (52.7% and 60.9%, respectively) to the period from 1996 to 2000 (61.8% and 73.4%, respectively), whereas there was little improvement for ARMS (40.1% and 47.8%, respectively).

CONCLUSIONS

Observed differences in incidence and survival for 2 major RMS subtypes across sex and age subgroups further supported the hypothesis that there are unique underlying etiologies for these tumors. Exploration of these differences presents an opportunity to increase current knowledge of RMS.

Adult Laryngeal Rhabdomyosarcoma: is aggressive treatment justified in all cases? A case report and review of the literature

Background:

Adult laryngeal rhabdomyosarcomas are rare tumours commonly treated by laryngectomy.

Case report:

We present a case of subglottic laryngeal rhabdomyosarcoma in an elderly woman, treated by endoscopic resection.

Conclusion:

Despite the fact that this tumour is traditionally treated aggressively, this approach is not supported by the literature. Due to the varying biological behaviour of this tumour in adults, we believe that conservative surgical procedures or combination therapies should be preferred, rather than total laryngectomy.

Mixed embryonal/alveolar rhabdomyosarcoma of the prostate: report of a case with molecular genetic studies and literature review

Alveolar rhabdomyosarcoma (RMS) is 1 of 2 main subtypes of RMS in the pediatric age group and tends to occur in the extremities. The urogenital tract is another common site for RMS, but this typically involves the embryonal subtype including sarcoma botryoides. We report a 28-year-old male with a prostatic tumor that was excised en bloc and showed a RMS with separate areas of embryonal and solid alveolar morphologies at the light microscopic level. Both areas showed diffuse nuclear expression for myogenin, and both areas expressed the PAX3-FKHR fusion gene, a genetic change associated with alveolar but not embryonal RMS. A review of the literature documented only 5 cases of RMS primary to the prostate showing alveolar or mixed histology. Ours is the 6th case and the 1st with molecular findings. Although the diagnostic category of mixed embryonal/alveolar RMS remains in use, the nature of this type of RMS is incompletely understood. In our case, although the morphology was mixed embryonal/alveolar, at the genetic level this tumor was alveolar in nature.

Pediatric urologic rhabdomyosarcoma

PURPOSE OF REVIEW

To review on the most significant and recent developments in basic research, diagnostic, and therapeutic aspects of genitourinary rhabdomyosarcomas (RMS) in children.

RECENT FINDINGS

Collaborative studies have dramatically improved therapy of genitourinary RMS with a remarkable improvement of survival. However, refractory or relapsed disease is still the most demanding challenge. Advances in our understanding of RMS molecular biology evolve new risk stratification and new therapeutic targets such as growth factors and their receptors. High-quality imaging is crucial and integrated fluorodeoxyglucose positron emission tomography/computed tomography significantly increased sensitivity. Alternative chemotherapeutical strategies were proven. Mutilating primary surgery should be avoided. Modern irradiation modalities with decrease of local radiation dose and, therefore, less long-term effects are new tools in the therapeutic arsenal of therapists.

SUMMARY

Therapy-associated morbidity after current RMS treatment can be significantly decreased by including modern strategies, especially in the field of irradiation. However, the follow-up is too short so far to make a distinct decision. The advances in understanding tumor biology may give rise to clinically relevant new therapeutic targets in the near future.

Management of paediatric sinonasal rhabdomyosarcoma

BACKGROUND AND AIM

Rhabdomyosarcoma is the commonest malignant tumour of the nose and paranasal sinuses in the paediatric population. Due to its rarity and largely unknown biological behaviour, the treatment of this tumour is complex and controversial. We present the results of multimodality treatment of paediatric sinonasal rhabdomyosarcoma, and we explore the role of surgery in the management of this malignancy.

METHODS

We retrospectively reviewed the records of 14 patients (median age 7.5 years) with sinonasal rhabdomyosarcoma. Six patients underwent major surgery with post-operative chemoradiation. Eight patients received multi-agent chemotherapy and radiotherapy. The mean follow-up time was 58 months (range seven to 276 months).

RESULTS

The five-year overall survival rates for all patients and for the surgery group were 53.9 and 83.3 per cent, respectively. All patients with alveolar rhabdomyosarcoma had a poor prognosis, with a median survival time of 17 months. Intracranial extension and an age greater than 10 years were also associated with an unfavourable outcome. Non- or partial responders to initial chemoradiation died within a year of diagnosis.

CONCLUSIONS

Management of paediatric rhabdomyosarcoma requires a combination of chemotherapy, radiotherapy and surgery. Primary chemoradiotherapy is the established treatment approach for advanced tumours. Early stage tumours with favourable histology can be treated successfully with radical surgery, provided that function and cosmetic appearance are preserved.

Sclerosing rhabdomyosarcoma of the parotid gland in an adult

Primary rhabdomyosarcoma of salivary glands is an extremely rare neoplasm, mostly seen in children. A newly described subtype of rhabdomyosarcoma, sclerosing rhabdomyosarcoma, has not yet been reported in this location. We report on a parotid gland tumor characterized by infiltrative growth of primitive type of neoplastic cells showing strong and diffuse nuclear positivity for MyoD1 and myogenin and by prominent hyalinized/chondroid matrix with some myxoid foci. The tumor recurred several times, and in recurrent tumors, differentiation into strap myoid cells appeared. There were no distant metastases during the 5-year follow-up. Sclerosing rhabdomyosarcoma may cause differential diagnostic problems because it could be confounded for osteosarcoma, chondrosarcoma, and some other types of sarcoma, and as in our case, for myxofibrosarcoma and myoepithelial carcinoma. Its location in the head and neck is of special interest because 6 of 14 previously described adult cases of sclerosing rhabdomyosarcoma and 7 of 18 pediatric cases also occurred in this region. To our knowledge, this is the first reported case of primary sclerosing rhabdomyosarcoma of the parotid gland.

Treatment of Nonmetastatic Cranial Parameningeal Rhabdomyosarcoma in Children Younger Than 3 Years Old: Results From International Society of Pediatric Oncology Studies MMT 89 and 95

Purpose

To explore a strategy by which radiotherapy (RT) could be avoided in the treatment of young children with parameningeal rhabdomyosarcoma (PM RMS).

Patients and Methods

Fifty-nine children (median age, 2 years 3 months) with nonmetastatic cranial PM RMS were treated in the International Society of Pediatric Oncology MMT 89 and 95 trials between 1989 and 2003.

Results

Five-year EFS and OS rates were 46% and 54%, respectively, for the whole group. No standard clinical or pathologic variables had prognostic impact. Fifty (85%) of 59 patients achieved complete local control either with (n = 28) or without (n = 22) RT administered as part of their primary treatment. Nine patients (15%) did not achieve local control (four of whom had had RT), and all died. Patients who received RT had a significantly superior 5-year EFS rate compared with patients who did not receive RT (59% v 28%, respectively). Twenty-three patients (48%) experienced relapse at a median interval of 15 months. Ultimately, only seven patients (12%) were cured without RT, although this represented 32% of those who achieved local control with initial chemotherapy.

Conclusion

Despite concerns about the late effects of its use in young children, cure of PM RMS remains unlikely without systematic use of RT. The accurate prediction of the small subset of patients who achieve local control without RT and who do not experience relapse would provide an opportunity for a minority of patients to avoid RT.

Molecular classification of rhabdomyosarcoma--genotypic and phenotypic determinants of diagnosis: a report from the Children's Oncology Group

Rhabdomyosarcoma (RMS) in children occurs as two major histological subtypes, embryonal (ERMS) and alveolar (ARMS). ERMS is associated with an 11p15.5 loss of heterozygosity (LOH) and may be confused with nonmyogenic, non-RMS soft tissue sarcomas. ARMS expresses the product of a genomic translocation that fuses FOXO1 (FKHR) with either PAX3 or PAX7 (P-F); however, at least 25% of cases lack these translocations. Here, we describe a genomic-based classification scheme that is derived from the combined gene expression profiling and LOH analysis of 160 cases of RMS and non-RMS soft tissue sarcomas that is at variance with conventional histopathological schemes. We found that gene expression profiles and patterns of LOH of ARMS cases lacking P-F translocations are indistinguishable from conventional ERMS cases. A subset of tumors that has been histologically classified as RMS lack myogenic gene expression. However, classification based on gene expression is possible using as few as five genes with an estimated error rate of less than 5%. Using immunohistochemistry, we characterized two markers, HMGA2 and TFAP2ss, which facilitate the differential diagnoses of ERMS and P-F RMS, respectively, using clinical material. These objectively derived molecular classes are based solely on genomic analysis at the time of diagnosis and are highly reproducible. Adoption of these molecular criteria may offer a more clinically relevant diagnostic scheme, thus potentially improving patient management and therapeutic RMS outcomes.

Prevalence and clinical impact of anaplasia in childhood rhabdomyosarcoma : a report from the Soft Tissue Sarcoma Committee of the Children's Oncology Group

BACKGROUND

Anapalsia is rare in childhood rhabdomyosarcoma and has not been included in the International Classification of Rhabdomyosarcoma (ICR). A recent review of cases from the Soft Tissue Sarcoma Committee of the Children's Oncology Group (COG) suggests that anaplasia might be more common than previously reported and may impact clinical outcome.

METHODS

The prevalence of anaplasia (focal or diffuse) was prospectively assessed in 546 eligible cases who were registered in an Intergroup Rhabdomyosarcoma Study Group (IRSG) or COG therapeutic trial from 1995 through 1998. The incidence of anaplasia in tumor samples and its impact in predicting clinical outcome was assessed.

RESULTS

Overall, 71 (13%) of all samples analyzed had anaplasia. Anaplasia was more common in patients with tumors in favorable sites and was less commonly observed in younger patients and in those with stage II, III, or clinical group III disease. Regardless of its distribution (focal or diffuse), on univariate analysis the presence of anaplasia negatively influenced the failure-free survival rate (63% vs 77% at 5 years) and overall survival (68% vs 82% at 5 years) rates in patients with embryonal rhabdomyosarcoma. This effect was most pronounced in children with intermediate-risk tumors. Anaplasia did not affect outcome in patients with alveolar tumors.

CONCLUSIONS

The incidence of anaplasia in patients with rhabdomyosarcoma is higher than previously described and may be of prognostic significance in children with intermediate-risk embryonal rhabdomyosarcoma.

Ischemic fasciitis: analysis of 44 cases indicating an inconsistent association with immobility or debilitation

Ischemic fasciitis is a rare pseudosarcomatous proliferation of atypical fibroblasts described to be located over bony protuberances and said to develop most often in immobile elderly or debilitated patients. We report the clinicopathologic features of 44 cases of this pseudosarcomatous reactive fibroblastic/myofibroblastic proliferation. There were 15 female and 29 male patients between 23 and 96 years of age (median: 74 y). Tumor size, known in 34 cases, ranged from 1.3 to 10 cm (median: 4.7 cm). The lesions developed mostly in the deep subcutis (27 cases) and infiltration of deep dermis, muscle, and tendinous tissue was sometimes observed. In 3 cases, the lesion developed within skeletal muscle. In 33 cases (76.7%), the tumor was located around the limb girdles and sacral region; 5 tumors each (23.3%) occurred on the chest wall and the back. A history of physical debilitation could be confirmed in only 7 patients. Nine patients had a history of chronic or malignant diseases and 4 patients had a history of local trauma. The histologic hallmark of this reactive proliferation is a zonal appearance with central fibrinoid degeneration/necrosis and cystic changes surrounded by a granulation tissuelike vascular component, mixed with plump amphophilic reactive fibroblasts and myofibroblasts morphologically similar to proliferative fasciitis. Immunohistochemistry was performed in 18 cases, showing focal positivity for smooth muscle actin (37.5%), desmin (40%), or both (14.3%), underlining the fibroblastic/myofibroblastic nature of these lesions, whereas S-100 and Pan-keratin were consistently negative. Follow-up data were available in 13 cases and ranged between 6 and 72 months (median: 31.3 mo); local recurrence was observed in 1 case in which the patient was physically debilitated. Recognition of this distinct entity as a reactive process, by no means always associated with debilitation, is essential to avoid confusion with soft tissue sarcomas.

Diffuse myogenin expression by immunohistochemistry is an independent marker of poor survival in pediatric rhabdomyosarcoma: a tissue microarray study of 71 primary tumors including correlation with molecular phenotype

The pathologic classification of rhabdomyosarcoma (RMS) into embryonal or alveolar subtype is an important prognostic factor guiding the therapeutic protocol chosen for an individual patient. Unfortunately, this classification is not always straightforward, and the diagnostic criteria are controversial in a subset of cases. Ancillary studies are used to aid in the classification, but their potential use as independent prognostic factors is rarely studied. The aim of this study is to identify immunohistochemical markers of potential prognostic significance in pediatric RMS and to correlate their expression with PAX-3/FKHR and PAX-7/FKHR fusion status. A single tissue microarray containing 71 paraffin-embedded pediatric RMSs was immunostained with antibodies against p53, bcl-2, Ki-67, CD44, myogenin, and MyoD1. The tissue microarray and whole paraffin blocks were studied for PAX-3/FKHR and PAX-7/FKHR gene fusions by fluorescence in situ hybridization and reverse transcription-polymerase chain reaction. Clinical follow-up data were available for each patient. Immunohistochemical staining results and translocation status were correlated with recurrence-free interval (RFI) and overall survival (OS) using the Kaplan-Meier method, the log-rank test, and Cox proportional hazard regression. The minimum clinical follow-up interval was 24 months (median follow-up=57 mo). On univariable analysis, immunohistochemical expression of myogenin, bcl-2, and identification of a gene fusion were associated with decreased 5-year RFI and 10-year OS (myogenin RFI P=0.0028, OS P=0.0021; bcl-2 RFI P=0.037, OS P=0.032; gene fusion RFI P=0.0001, OS P=0.0058). After adjustment for Intergroup Rhabdomyosarcoma Study-TNM stage, tumor site, age, tumor histology, and translocation status by multivariable analysis, only myogenin retained an independent association with RFI (P=0.034) and OS (P=0.0069). In this retrospective analysis, diffuse immunohistochemical reactivity for myogenin in RMS correlates with decreased RFI and OS, independent of histologic subtype, translocation status, tumor site, or stage.

Results in patients with cranial parameningeal sarcoma and metastases (Stage 4) treated on Intergroup Rhabdomyosarcoma Study Group (IRSG) Protocols II-IV, 1978-1997: report from the Children's Oncology Group

PURPOSE

Determine outcome of patients with cranial parameningeal sarcoma and concurrent metastases treated on Intergroup Rhabdomyosarcoma Study Group (IRSG) Protocols II-IV.

PATIENTS

We identified 91 patients in the database, which includes newly diagnosed subjects <21 years old with rhabdomyosarcoma (RMS) and undifferentiated sarcoma, and reviewed their charts in detail.

RESULTS

The 54 males and 37 females were <1-19 years at diagnosis. Primary sites were nasopharynx-nasal cavity, middle ear/mastoid and parapharyngeal area ("better" sites, 55%), paranasal sinus and infratemporal-pterygopalatine area ("worse" sites, 42%), and other (3%). Sixty-eight percent of informative patients had direct intracranial extension. Major metastatic sites at diagnosis were lung (63%), bone marrow (33%), and bone (27%). Treatment included vincristine, actinomycin D, and cyclophosphamide (VAC) chemotherapy and radiotherapy to the primary tumor and up to five metastatic sites/tissues.

OUTCOME

The estimated 10-year failure-free survival (FFS) rate was 32% (95% confidence interval [CI]: 22%, 42%). Sixty patients had progressive disease (N = 49) or death as a first event (N = 11); another developed myelodysplastic syndrome and died. Sites of first progression/relapse were distant (55%), local (12%), CNS extension (8%), mixed (6%), and uncertain (18%). Factors indicating likelihood of 10-year FFS included tumor arising in "better" versus "worse" sites (FFS 46% vs. 18%, P = 0.02) and embryonal versus other histology (FFS 37% vs. 19%, P = 0.06).

CONCLUSIONS

Cure was possible for some patients with metastatic cranial parameningeal sarcoma. Patients with the best outlook had embryonal RMS located in the nasopharynx/nasal cavity, middle ear/mastoid, or parapharyngeal region. Distant metastases were the most frequent type of recurrence, indicating that more effective systemic agents are needed to eliminate residual disease.

Primary rhabdomyosarcoma of the sacrum: a case report and review of the literature

We describe herein a rare case of primary rhabdomyosarcoma (RMS) occurring in the sacrum. A 16-year-old woman presented with a 2-month history of pain in bilateral buttocks and posterior thighs. Computed tomography showed a primary tumor with bone destruction in the 2nd sacral vertebra and invasion to the 1st to 3rd vertebrae and retroperitoneal space. Histological examination of the tumor showed proliferation of spindle-shaped cells intermingled with rhabdomyoblasts in a fascicular and storiform growth pattern. Tumor cells showed immunoreactivity for vimentin, desmin, muscle-specific actin, sarcomeric actin, alpha-smooth muscle actin and CD99, and partial immunoreactivity for myoD1, myf-4, myogenin and myoglobin. Reverse transcription polymerase chain reaction demonstrated expression of myoD1. On the basis of the aforementioned findings, a poorly differentiated spindle cell variant of embryonal RMS was diagnosed. The patient underwent combined therapy with chemotherapy and radiotherapy, but died 17 months after incisional biopsy. The present case is instructive in differential diagnosis of primary bone tumors, and the possibility of skeletal RMS needs to be considered.

Aberrant expression of epithelial and neuroendocrine markers in alveolar rhabdomyosarcoma: a potentially serious diagnostic pitfall

Alveolar rhabdomyosarcoma may be extremely difficult to distinguish from other primitive round cell neoplasms without ancillary immunohistochemistry and/or genetic study. Particularly in adults and in the head and neck locations, the differential diagnosis of alveolar rhabdomyosarcoma includes small cell carcinoma and neuroepithelial tumors, such as esthesioneuroblastoma. We have recently seen cases of genetically confirmed alveolar rhabdomyosarcoma, which were misdiagnosed owing to expression of cytokeratins and neuroendocrine markers. We studied a large group of well-characterized alveolar rhabdomyosarcomas for expression of such markers. Forty-four alveolar rhabdomyosarcomas (18 genetically confirmed) were retrieved from our archives and immunostained for wide-spectrum cytokeratin (OSCAR), low molecular weight cytokeratin (Cam5.2), synaptophysin, chromogranin A, and CD56 using commercially available antibodies. Cases were scored as 'negative', 'rare' (<5% positive cells), '1+' (5-25%), '2+' (26-50%) and '3+' (>51%). The tumors occurred in 23 males and 21 females at a mean age of 18 years (range, <1-64 years), and involved many sites. Fifty percent of cases (22 of 44) expressed wide-spectrum cytokeratin, and scored almost equally as rare, 1+, and 2+, but rarely 3+. Cam5.2 was positive in 52% (14 of 27). Forty-three percent of cases (16 of 37) expressed at least one of the specific neuroendocrine markers, 32% (12 of 37) expressed synaptophysin, 22% (eight of 36) expressed chromogranin A, and 11% expressed both. Expression of synaptophysin and chromogranin A was typically confined to rare cells but could be more widespread. Thirty-two percent of cases (12 of 37) expressed the wide-spectrum cytokeratin and at least one of the neuroendocrine markers, and 8% (three of 36) expressed cytokeratin and both neuroendocrine markers. CD56 expression was nearly ubiquitous. Aberrant expression of epithelial and neuroendocrine markers is relatively common in alveolar rhabdomyosarcoma, occurring in 30-40% of cases. These findings have significant implications for the diagnosis of alveolar rhabdomyosarcoma, particularly in adults and in the head and neck locations. Although expression of cytokeratin and/or synaptophysin alone does not necessarily indicate epithelial or neuroendocrine differentiation, coexpression of cytokeratin and neuroendocrine markers, and in particular the presence of chromogranin expression, suggest true epithelial and/or neuroendocrine differentiation in a subset of alveolar rhabdomyosarcomas. CD56 is not a specific neuroendocrine marker, and should not be used in the absence of synaptophysin/chromogranin. These findings emphasize the need to employ a panel of markers, to include desmin, myogenin/MyoD1, and genetic study in the diagnosis of primitive round cell neoplasms in all age groups and in all locations.

Imaging findings in noncraniofacial childhood rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood. This paper is focuses on imaging for diagnosis, staging, and follow-up of noncraniofacial RMS.

The role of radiology in paediatric soft tissue sarcomas

Paediatric soft tissue sarcomas (STS) are a group of malignant tumours that originate from primitive mesenchymal tissue and account for 7% of all childhood tumours. Rhabdomyosarcomas (RMS) and undifferentiated sarcomas account for approximately 50% of soft tissue sarcomas in children and non-rhabdomyomatous soft tissue sarcomas (NRSTS) the remainder. The prognosis and biology of STS tumours vary greatly depending on the age of the patient, the primary site, tumour size, tumour invasiveness, histologic grade, depth of invasion, and extent of disease at diagnosis. Over recent years, there has been a marked improvement in survival rates in children and adolescents with soft tissue sarcoma and ongoing international studies continue to aim to improve these survival rates whilst attempting to reduce the morbidity associated with treatment. Radiology plays a crucial role in the initial diagnosis and staging of STS, in the long term follow-up and in the assessment of many treatment related complications. We review the epidemiology, histology, clinical presentation, staging and prognosis of soft tissue sarcomas and discuss the role of radiology in their management.

Imaging of cell trafficking and metastases of paediatric rhabdomyosarcoma

OBJECTIVE

The aim of this study was to establish a preclinical mouse model to study metastases of paediatric rhabdomyosarcoma at the macroscopic and cellular levels, with different imaging methods.

EXPERIMENTAL DESIGN

The alveolar rhabdomyosarcoma cell line Rh30 was stably transfected with the red fluorescent protein (DsRed2) then was xenotransplanted (intravenous injection [n = 8], and footpad injection [n = 8]) into nude mice (NMRI nu/nu). Macroscopic imaging of metastases was performed using DsRed2-fluorescence and flat-panel volumetric computed tomography scan. In a further series of animals (n = 8), in vivo cell trafficking of rhabdomyosarcoma cells using cellular imaging with an Olympus OV100 variable-magnification small-animal imaging system was used.

RESULTS

Metastases in the pelvis, thoracic wall and skin were visualized by fluorescence imaging. Pelvic metastases were found after tail vein injection and at other metastatic sites after footpad injection. Flat-panel volumetric computed tomography scan data allowed highly specific analysis of contrast between tumour and surrounding tissue. Correlation between fluorescence and flat-panel volumetric computed tomography scan imaging data was observed. Single-cell imaging visualized tumour cells in the vessels and demonstrated the arrest of tumour cells at vessel junctions followed by extravasation of the tumour cells.

CONCLUSION

We established a model for visualization of experimental metastatic invasion and describe relevant tools for imaging childhood rhabdomyosarcoma metastases at the macroscopic and cellular levels. Imaging of cell trafficking visualized the behaviour of tumour cells and development of metastases by accumulation and extravasation of rhabdomyosarcoma cells.

Molecular biology of rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is one of the most common extracranial solid tumours in children. Embryonal and alveolar subtypes of RMS present completely different genetic abnormalities. Embryonal RMS (eRMS) is characterised by loss of heterozygosity on the short arm of chromosome 11 (11p15.5), suggesting inactivation of a tumour-suppressor gene. In contrast, the majority (80-85%) of the alveolar RMS (aRMS) have the reciprocal chromosomal translocations 't(2;13)(q35;q14) or t(1;13)(p36;q14). t(2;13) appears in approximately 70% of patients with the alveolar subtype. The molecular counterpart of this translocation consists of the generation of a chimeric fusion gene involving the /PAX3/ gene located in chromosome 2 and a member of the fork-head family, /FOXO1/ (formerly /FKHR/), located in chromosome 13. A less frequent variant translocation t(1;13) involves another PAX family gene, /PAX7/, located in chromosome 1 and /FOXO1/ and is present in 10-15% of cases of the alveolar subtype in RMS. Recently, many studies focused on cancer have demonstrated the great potential of the genomic approach based on tumour expression profiles. These technologies permit the identification of new regulatory pathways. Molecular detection of minimal disease by a sensitive method could contribute to better treatment stratification in these patients. In RMS, the advances in the knowledge of the biological characteristics of the tumour are slowly translated into the clinical management of children with this tumour.

Cyto-histological correlations in primary, recurrent and metastatic rhabdomyosarcoma: the institut Curie's experience

To determine diagnostic cytomorphologic features of rhabdomyosarcoma (RMS) on fine-needle aspiration (FNA) material, the cytologic material and corresponding histologic slides of 180 tumors obtained from 109 patients were reviewed. Fifty eight (32.2%) tumors were primary, 34 (18.9%) recurrent, and 88 (48.9%) metastatic. A review of original cytology reports revealed that 176 of 180 (97.8%) tumors were either diagnosed accurately or as round cell sarcoma, while 3 (1.7%) were reported as suspicious. In one case (0.5%), the material was unsatisfactory. No false negative samples were seen. When FNA morphology was correlated with different histological subtypes, the alveolar subtype RMSs were more cellular than the nonalveolar ones (91.4% vs. 64.9%). Similarly, alveolar subtype RMSs compared with nonalveolar ones exhibited more rhabdomyoblastic cells (77.1% vs. 52.7%), alveolar structures (67.6% vs. 10.8%), giant, multinucleated cells (22.9% vs. 6.7%), mitotic figures (57.1% vs. 18.9%), and cyto-nuclear atypia (77.1% vs. 43.2%). Inversely, spindle-shaped cells were more frequently seen in nonalveolar versus alveolar RMSs (37.8% vs. 20.9%).

Orbital rhabdomyosarcoma

BACKGROUND

Although rhabdomyosarcoma (RMS) is a rare tumor among the entire group of mesenchymal malignancies, it is a relatively common lesion and significant challenge for the ocular oncologist in terms of its diagnosis and management.

METHODS

A comprehensive literature search of articles published over the past 30 years in PubMed was conducted.

RESULTS

Orbital RMS usually presents as a space-occupying lesion in the orbit during the first decade and may mimic other neoplastic or inflammatory masses. The tumor has predilection for the superior nasal quadrant of the orbit. The clinical manifestations depend on the location of the tumor within the orbit and its rate of growth. The common histopathologic types are embryonal and alveolar varieties. CT and MR imaging are important in the evaluation of this tumor. Particular attention should be placed on the bone invasion and extension of the tumor into the intracranial cavity and paranasal sinuses. Treatment usually consists of a combination of chemotherapy and radiation therapy following excisional biopsy.

CONCLUSIONS

Survival of orbital RMS has improved due to advances in chemotherapy and radiotherapy. Posttreatment complications, including side effects of radiotherapy and secondary orbital malignancies, as well as visual dysfunction, occur more often and present new challenges due to improved long-term survival.

Adult rhabdomyosarcoma: cross-sectional imaging findings including histopathologic correlation

OBJECTIVE

The purpose of our study was to present the MRI and CT features of adult rhabdomyosarcomas with histopathologic correlation. Forty-nine sequential cases were incorporated over a 5-year period from the sarcoma unit database. Twenty-six patients had adequate imaging (16 MRI, 10 CT) and histopathology available for retrospective review. The alveolar subtype was present in 13 patients, embryonal subtype in four patients, and pleomorphic subtype in nine patients. On both CT and T1-weighted MRI, all tumors were isodense to skeletal muscle, although enhancement was variable after the administration of IV contrast material. Pleomorphic tumors were very high signal on T2-weighted/STIR imaging, and both pleomorphic and alveolar subtypes were extremely heterogeneous. Embryonal tumors were more homogeneous.

CONCLUSION

Although adult rhabdomyosarcomas have certain imaging appearances in common with other soft-tissue sarcomas, features at presentation such as tumor heterogeneity, site, regional lymphadenopathy, and pulmonary metastasis should make the radiologist consider this important diagnosis.

Pediatric surgical oncology: management of rhabdomyosarcoma

A malignant tumor of striated muscle origin, Rhabdomyosarcoma (RMS) is a childhood tumor that has benefited from 30 years of multimodality therapeutic trials culminating in a greater than 70% overall current 5-year survival. Prognosis for RMS is dependent on anatomic primary tumor site, age, completeness of resection, presence and number of metastatic sites, histology and biology of the tumor cells. Multimodality treatment is based on risk stratification according to pretreatment stage, postoperative group, histology and site. Therefore, pretreatment staging is vital for assessment and is dependent on primary tumor site, size, regional lymph node status, and presence of metastases. Unique to RMS is the concept of postoperative clinical grouping that assesses the completeness of disease resection and takes into account lymph node evaluation both at the regional and metastatic basins. At all sites, if operative resection of all disease is accomplished, including microscopic disease, survival is improved. Therefore, the surgeon plays a vital role in determining risk stratification for treatment and local control of the primary tumor for RMS.

Soft tissue tumors of the urinary bladder Part II: malignant neoplasms

Most bladder tumors arise from the urothelium. However, there are several uncommon but significant malignant bladder lesions that must be differentiated from urothelial carcinomas and from benign lesions of the bladder. The second half of this two-part review will describe rare nonurothelial malignant tumors of the urinary bladder including leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, malignant fibrous histiocytoma (undifferentiated sarcoma), primitive neuroectodermal tumor, malignant peripheral nerve sheath tumor, hemangiopericytoma, and alveolar soft-parts sarcoma. Common clinical presentations, morphologic characteristics, and immunohistochemical features are described to aid the practicing pathologist in the identification of these entities. Because the distinction between malignant and benign lesions has significant therapeutic and prognostic implications, key factors for differentiating them are presented.