Clinicopathologic study of ectomesenchymomas from Intergroup Rhabdomyosarcoma Study Groups III and IV

Rhabdomyosarcoma: Updates on classification and the necessity of molecular testing beyond immunohistochemistry

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents under the age of 20. The current World Health Organization (WHO) classification for soft tissue and bone tumors recognizes 4 distinct subtypes of RMS based on clinicopathological and molecular genetic features: embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. However, with the increased use of molecular techniques, the classification of rhabdomyosarcoma has been evolving rapidly. New subtypes such as osseus RMS harboring TFCP2/NCOA2 fusions or RMS arising in inflammatory rhabdomyoblastic tumor have been emerging within the last decade, adding to the complexity of diagnosing skeletal muscle tumors. This review article provides an overview of classically recognized distinctive subtypes as well as new, evolving subtypes and discusses important morphologic, immunophenotypic and molecular genetic features of each subtype including recommendations for a diagnostic approach of malignant skeletal muscle neoplasms.

An integrative morpho-molecular approach in malignant ectomesenchymoma diagnosis: report of a new paediatric case and a review of the literature

Introduction

Malignant ectomesenchymoma (MEM) is a soft tissue tumour, consisting of both malignant neuroectodermal elements and one or more mesenchymal elements.

Case presentation and review of the literature

Here we describe the case of a 6-months-old male, previously treated in another hospital for abdominal rhabdomyosarcoma (RMS). Histological re-examination demonstrated that the tumour had mesenchymal and neuroectodermal elements components, with a new diagnosis of abdominal-pelvic MEM. A Next-Generation Sequencing (NGS) analysis was performed on a surgical tumour specimen and revealed the presence of a somatic mutation, already reported in MEM cases. We carried out a review of the literature and we found 33 new cases of MEM since the last review. We reported the clinic-pathologic features of new cases of MEM, highlighting the role of molecular studies in supporting the diagnosis of this ambiguous tumours.

Conclusion

We promote the importance of a diagnosis based on an integrative morpho-molecular approach, that routinely include molecular analysis and the use of bioinformatic mutation detection tools, to support diagnostic and therapeutical queries and to highlight tumour biology and behaviour.

First Reported Case of Malignant Ectomesenchymoma with p.Leu122Arg Mutation in MYOD1 Gene: Extensive Intra- and Extracranial Tumor in a 15-Year-Old Female

BACKGROUND

Ectomesenchymomas (EMs) are extremely rare neoplasms composed of malignant mesenchymal components and neuroectodermal derivatives. They are described in a wide variety of locations, with the head and neck region being one of the most frequently involved areas. EMs are usually managed as high-risk rhabdomyosarcomas and have similar outcomes.

METHODS

We present the case of a 15-year-old female with an EM that arose in the parapharyngeal space and extended into the intracranial space.

RESULTS

Histologically, the tumor presented an embryonal rhabdomyosarcomatous mesenchymal component and the neuroectodermal component was constituted by isolated ganglion cells. Next-generation sequencing (NGS) revealed a p.Leu122Arg (c.365 T > G) mutation in the MYOD1 gene, a p.Ala34Gly mutation in the CDKN2A gene, and CDK4 gene amplification. The patient was treated with chemotherapy. She died 17 months after the debut of symptoms.

CONCLUSION(S)

To our knowledge, this is the first reported case in English literature of an EM with this MYOD1 mutation. We suggest combining PI3K/ATK pathway inhibitors in these cases. NGS should be performed in EMs cases to detect mutations with potential treatment options.

Malignant ectomesenchymoma in children: The European pediatric Soft tissue sarcoma Study Group experience

Malignant ectomesenchymoma (MEM) is an extremely rare soft tissue tumor typical of young children, currently included in the category of skeletal muscle malignancies and characterized by a neuroblastic component. This study describes a series of 10 patients prospectively registered in the European paediatric Soft tissue sarcoma Study Group (EpSSG) database Of the 10 cases, seven had an initial local diagnosis of rhabdomyosarcoma. All patients received chemotherapy according to rhabdomyosarcoma strategy, four had radiotherapy. Overall, six patients were alive in first remission, two in second remission and one after second tumor. Only the patient with initially metastatic tumor died of disease.

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 2: vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5^th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous organ soft tissues, as well as the peripheral and autonomic nervous system.

More Than Meets the Eye? A Cautionary Tale of Malignant Ectomesenchymoma Treated as Low-risk Orbital Rhabdomyosarcoma

Malignant ectomesenchymoma (MEM) is a rare multiphenotypic tumor comprised of mesenchymal and neuroectodermal components. MEM is typically diagnosed in infants and younger children and outcomes are variable. The current approach for treating MEM includes targeting the more aggressive mesenchymal component of the tumor, which is often rhabdomyosarcoma. Here, we describe a case of an orbital tumor initially diagnosed and treated as low-risk rhabdomyosarcoma. Local failure prompting a second biopsy revealed neuronal differentiation consistent with a diagnosis of MEM. Intensifying therapy and local radiotherapy led to a long-term cure. This case offers a cautionary tale that while outcomes for MEM were similar to matched rhabdomyosarcoma cohorts when treated on conventional Intergroup Rhabdomyosarcoma Study Group (IRSG) III/IV protocols, treating MEM using a decreased intensity low-risk rhabdomyosarcoma regimen may not be sufficient.

Primary uterine ectomesenchymoma harboring a DICER1 mutation: case report with molecular analysis

Ectomesenchymoma is an exceedingly rare biphasic malignant tumor characterized by the presence of mesenchymal and neuroectodermal elements. The majority of patients are infants or children. We describe the first case of this entity diagnosed as a primary uterine tumor. A 72-year-old female presented with post-menopausal bleeding. Dilatation and curettage showed irregular mesenchymal proliferation of uncertain nature. In the hysterectomy specimen, a myxoid spindle cell tumor with areas of skeletal muscle and neural differentiation was found in the uterus, with direct invasion of the small intestine, and biphasic differentiation into rhabdomyosarcoma and ganglioneuroblastoma was unequivocally seen in a lymph node metastasis. The morphological findings were validated by immunohistochemistry. Massive parallel sequencing identified TP53, PTEN, and DICER1 mutations in the tumor. This report describes the presence of ectomesenchymoma in an unusual primary organ and in an uncharacteristic age and presents novel data regarding the genetic characteristics of this tumor.

Primary intracranial malignant ectomesenchymoma in an adult: Report of a rare case and review of the literature

Malignant ectomesenchymoma (MEM) is an exceedingly rare rapidly progressing tumor of soft tissues of the central nervous system, believed to be derived from neural crest cells. The majority of cases have been observed in young children or adolescents. So far only 11 patients with intracranial manifestations (with confirmed clinicopathological data) have been documented. We report the first case of adult intracranial MEM in a 54-year-old man who presented with a 4 months history of headache and weakness of right side of the body. Magnetic resonance imaging showed a homogenously enhanced dural-based lesion in the left fronto-temporo-parietal lobe with significant perilesional edema and mass effect. No metastatic disease was identified and the lesion was grossly resected. Histopathological and immunohistochemical examination revealed mature and immature neurons and bizarre astrocytes admixed with a mesenchymal spindle cell (rhabdomyoblastic) component. Specific risk factors that contribute toward the development of MEM are unknown. Due to the scarcity of reported cases the role of adjuvant therapy is unclear.

Malignant Ectomesenchymoma: Series Analysis of a Histologically and Genetically Heterogeneous Tumor

AIMS

Malignant ectomesenchymoma is a rare pediatric neoplasm with dual mesenchymal and neuroectodermal elements. Mesenchymal component is usually rhabdomyosarcoma, particularly embryonal subtype, whereas neuroectodermal derivatives are frequently a neuroblastic tumor. Ectomesenchymoma manifests in various sites given the wide migration of neural crest cells during development, though the pelvis/perineum is most often involved. Moreover, no unique unifying molecular abnormality has been determined.

METHODS

We conducted a retrospective study to analyze the spectrum of ectomesenchymal tumors encountered in our pediatric population. Six patients were identified and data pertaining to patients' demographic, tumor size and site, histologic components with immunophenotypic profile, molecular alterations, treatment, and outcome were collected.

RESULTS

Mesenchymal elements, represented by rhabdomyosarcoma in all instances, were the dominant component in the majority of cases (5/6). Embryonal and alveolar morphology had similar distribution (3/6) and all patients with alveolar subtype harbored the characteristic translocations of this entity. The neuroectodermal component was most often a neuroblastic-like neoplasm (4/6); however, 2/6 cases demonstrated primitive neuroectodermal tumor-like morphology. No unifying alterations were found on molecular studies.

CONCLUSIONS

Our analysis extends the histologic and molecular spectrum of these tumors and highlights their heterogeneity. The percentage of cases with alveolar rhabdomyosarcoma or primitive neuroectodermal-like tumor components suggests that these types of elements might be underreported. This study is also the first to demonstrate FOXO1 gene rearrangements in malignant ectomesenchymoma with alveolar rhabdomyosarcoma subtype.

Frequent HRAS Mutations in Malignant Ectomesenchymoma: Overlapping Genetic Abnormalities With Embryonal Rhabdomyosarcoma

Malignant ectomesenchymoma (MEM) is an exceedingly rare pediatric sarcoma with a predilection for infants and young children and is composed of dual malignant mesenchymal and neuroectodermal components. Microscopically, MEM displays areas of rhabdomyosarcoma (RMS) with intermixed neuronal/neuroblastic foci. The molecular alterations associated with MEM and its relationship with embryonal RMS (ERMS) and malignant peripheral nerve sheath tumor (MPNST) have not yet been elucidated. In this study we used whole-transcriptome sequencing in 2 MEM index cases with available frozen tissue, followed by screening of the identified genetic abnormalities in 5 additional cases. No candidate fusion genes were detected by FusionSeq analysis; however, the mutation detection algorithms revealed HRAS and PTPRD hotspot mutations in both index cases, with 1 case harboring an additional FBXW7 mutation. As these mutation profiles have been previously described in ERMS we have tested their incidence in a control group of 7 age-matched ERMS. In addition, the gene signature of MEM was compared with that of RMS, MPNST, and neuronal lineage. All 7 MEM patients were male, with a mean age of 7.5 months (range, 0.6 to 17 mo). All except 1 occurred in the pelvic/urogenital region. Most cases showed ERMS elements, with occasional spindle or undifferentiated/round cell areas. The intermixed neuroectodermal components were mostly scattered ganglion cells, ganglioneuroma, or ganglioneuroblastoma. By Sanger sequencing, 6 of 7 (86%) MEMs had HRAS mutations, with no additional case harboring PTPRD or FBXW7 mutations. The only case lacking HRAS mutation showed neuroblastic micronodules without ganglion cells. The trimethylation at lysine 27 of histone H3 (H3K27me3) expression, typically lost in MPNST, was retained in all cases. In the control ERMS group, 5 of 7 (71%) showed RAS mutations, equally distributed among NRAS, KRAS, and HRAS genes. The expression profiling of MEM showed upregulation of skeletal muscle and neuronal genes, with no significant overlap with MPNST. Our results of common HRAS mutations and composite gene signature with RMS and neuronal/neuroblastic elements suggest a closer genetic link of MEM to RMS rather than to MPNST.

The Evolution of Pediatric Soft Tissue Sarcoma Classification in the Last 50 Years

This review discusses the history of the classification of soft tissue sarcomas in children and adolescents, the current transition toward integration of morphology and molecular genetics as new entities emerge, and future perspectives.

Metastatic malignant ectomesenchymoma initially presenting as a pelvic mass: report of a case and review of literature

Pediatric soft tissue sarcomas account for approximately 10% of all pediatric malignancies. Malignant ectomesenchymoma is rare biphasic sarcomas consisting of both mesenchymal and neuroectodermal elements. Approximately 64 cases have been reported in the literature and are believed to arise from pluripotent embryologic migratory neural crest cells. We report a 4-year-old boy who initially presented with a pelvic mass and inguinal lymphadenopathy at 6 months of age. Inguinal lymph node biopsy revealed a distinct biphasic tumor with microscopic and immunophenotypic characteristics diagnostic for both alveolar rhabdomyosarcoma and poorly differentiated neuroblastoma. The patient received national protocol chemotherapy against rhabdomyosarcoma with good response and presented with a cerebellar mass 21 months later. The metastatic tumor revealed sheets of primitive tumor cells and diagnostic areas of rhabdomyosarcoma and neuroblastoma were identified only by immunohistochemistry. Cytogenetic analysis of metastatic tumor demonstrated complex karyotype with multiple chromosomal deletions and duplications. The patient received national protocol chemotherapy against neuroblastoma and adjuvant radiotherapy after surgical resection of the cerebellar tumor with good response. He is currently off from any treatment for 18 months with no evidence of tumor recurrence or metastasis.

Ectomesenchymoma with embryonal rhabdomyosarcoma and ganglioneuroma, arising in association with benign triton tumor of the tongue

Soft-tissue tumors known as "triton" tumors are rare lesions containing neural tissue and skeletal muscle at varying levels of maturity and malignant potential. Benign triton tumors, also called "neuromuscular choristomas" or "neuromuscular hamartomas," consist of neural tissue containing mature skeletal muscle in intimate relationship with peripheral nerve. These tumors are rare in the head and neck in children. Ectomesenchymomas are similar tumors consisting of a malignant mesenchymal component, usually embryonal rhabdomyosarcoma, and a neuroectodermal component represented by mature ganglion cells or primitive neuroblastic/neuroectodermal foci (primitive ectomesenchymoma). Benign triton tumors have been regarded as benign, whereas ectomesenchymomas have been operationally considered to be variants of rhabdomyosarcoma. We present here a unique case that combines features of these 2 entities in a recurrent lesion on the tongue of a 35-month-old girl. This lesion raises questions about the "benign" nature of benign triton tumor and its possible relationship to ectomesenchymoma.

Malignant ectomesenchymoma in children and adolescents: report from the Cooperative Weichteilsarkom Studiengruppe (CWS)

BACKGROUND

Malignant ectomesenchymoma (MEM) is a soft tissue tumor with heterologous rhabdomyoblastic components believed to arise from pluripotent migratory neural crest cells. To date merely 50 cases have been published and the knowledge about the course of disease and optimal treatment is limited.

METHODS

Six patients with MEM were registered 1996-2009. The diagnosis was confirmed according to current criteria. Their treatment and outcome was analyzed.

RESULTS

The median age of the three females and three males was 0.6 years (range, 0.2-13.5). The mesenchymal component in all tumors was rhabdomyosarcoma (RMS), the neural component ganglioneuroblastoma/neuroblastoma (n = 5) and peripheral primitive neuroectodermal tumor in one case. Five patients presented with localized, one with metastatic disease. All but one patient received multiagent chemotherapy during their initial treatment. The tumors of 4/5 patients with localized MEM were at least grossly resected at best surgery; the patient without gross resection was additionally irradiated. Three of four evaluable tumors responded well to induction chemotherapy. All patients achieved a first complete remission (CR), but three recurrences (two local, one systemic) occurred. The individual with metastatic MEM did not survive, but all five patients with localized MEM are currently alive in CR with a median follow-up of 5 years (range: 2.1-13.7).

CONCLUSIONS

Risk-factors and outcome of MEM appear to be comparable with other highly malignant pediatric soft tissue sarcoma when a multimodal treatment strategy including chemotherapy and adequate local treatment is pursued. We propose that treatment of patients with MEM be done according to pediatric protocols similar to other rhabdomyosarcoma-like soft tissue sarcoma.

Epidemiological characteristics and survival studies of rhabdomyosarcoma in East egypt: a five-year multicenter study

Background. Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children, it represents 5–8% of childhood malignancies. Aim of the Work. To evaluate the epidemiological characteristics and treatment outcome in two pediatric oncology centers. Patients and Method. A retrospective analysis was performed on 41 medical records of children with RMS during 6 years period. Results. The median age of patients was 6 years with 80.4% below 10 years. Head and neck was the most common primary site. Embryonal RMS was the most frequent histopathologic subtype. Stage IV was the most frequent stage. According to IRS postsurgical grouping classification, group 4 was the most frequent group. There was a significant relationship between histopathologic subtypes of tumor and metastasis, primary site of tumor and histopathologic subtype, age, metastasis, IRS presurgical stage and IRS postsurgical group and outcome. The overall survival rate was 56.9% ± 8.4 and the failure free survival rate was 68.3% ± 7.6. Conclusion. The epidemiological characteristics of our patients are quite near to the worldwide data, apart from the higher prevalence of stage IV and group 4 with most of the primary tumor site in the extremities. CWS2002 protocol of therapy had led to improvement in the curability of the disease.

Myogenic tumors in children and adolescents

Neoplasms of striated and smooth muscle in children are a diverse group of neoplasms that have some unique aspects in contrast to these tumors in adults. Rhabdomyosarcoma is the most common soft tissue sarcoma of infancy and childhood and is relatively common in adolescents. In contrast, smooth muscle tumors are relatively rare, and the various types of rhabdomyoma and smooth and skeletal muscle hamartomas are very uncommon. In recent years, the understanding of the pathologic and genetic aspects of rhabdomyosarcoma has been enhanced by adjunct techniques, such as immunohistochemistry and cytogenetic or molecular genetic analysis. The current classification of rhabdomyosarcoma emphasizes the histologic-prognostic correlations. This article reviews the clinicopathologic features of striated and smooth muscle tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents and the differential diagnosis.

Ectomesenchymoma with t(1;12)(p32;p13) evolving from embryonal rhabdomyosarcoma shows no rearrangement of ETV6

Ectomesenchymoma is a rare mesenchymal malignancy occurring mainly in the pediatric population. The hallmark diagnostic features are a combination of sarcoma, usually rhabdomyosarcoma (RMS) with admixed ganglion cells. The lesion arises either in soft tissues or the cranial cavity, and outcomes vary considerably. Current knowledge about the genetics and biology of ectomesenchymoma is extremely limited with only 4 published karyotypes, showing overlaps only in trisomies 2, 8, and 11. Here, we describe a case with genetic findings that, in conjunction with preexisting observations, offer some additional insights into the genetic aberrations of ectomesenchymoma.

Ewing sarcoma/peripheral primitive neuroectodermal tumor and related tumors

Ewing sarcoma/peripheral primitive neuroectodermal tumor (EWS/pPNET) and other tumors with EWS gene rearrangements encompass a malignant and intermediate neoplasm with a broad anatomic distribution and a wide age range but a predilection for soft tissue in children, adolescents, and young adults. The overlapping histologic, immunohistochemical and cytogenetic and molecular genetic features create diagnostic challenges despite significant clinical and prognostic differences. Ewing sarcoma is the 3rd most common sarcoma in children and adolescents, and desmoplastic small round cell tumor is a rare neoplasm that occurs more often in older children, adolescents, and young adults. Pathologic examination is complemented by immunohistochemistry, cytogenetics, and molecular genetics. This article reviews the clinicopathologic features of EWS/pPNET and desmoplastic small round cell tumor in the spectrum of tumors with EWS gene rearrangements. Other tumors with different histopathologic features and an EWS gene rearrangement are discussed elsewhere in this volume.

A rare case of malignant pediatric ectomesenchymoma arising from the falx cerebri

Malignant ectomesenchymoma is a rare tumor arising from mature ganglion cells with immature myogenous elements, with only 4 pediatric intracranial cases having been previously reported. The authors report a rare case of intracranial malignant ectomesenchymoma originating from the falx cerebri in a 10-year-old boy. The patient presented with a 2-week history of headache, nausea, and blurry vision, with mild lateral gaze diplopia. A CT scan revealed a solitary 7.2 × 3.8-cm dural-based mass that extended along the falx. No metastatic disease was identified, and the lesion was grossly resected without complication. Pathological investigation identified single and small groups of cells in a myxoid background, with polygonal or spindle-shaped cells containing eccentric nuclei and prominent nucleoli. Immunohistochemical staining of some cells was positive for smooth-muscle actin, CD99, and vimentin, whereas other cells (often process forming) were positive for S100 protein, synaptophysin, and neurofilament protein. Staining was negative for CD138, CD45, α-fetoprotein, CK AE1/3, glial fibrillary acidic protein, CK7, CK20, CD31, CD34, myoD, and desmin. Normal immunopositivity was seen for INI-1. The Ki 67 immunostaining had < 25% reactivity. The patient was treated with a sarcoma-based chemotherapy regimen and radiation to the craniospinal axis, and was found to be without recurrence or metastatic disease at 20 months.

Pathobiologic markers of the ewing sarcoma family of tumors: state of the art and prediction of behaviour

Over the past three decades, the outcome of Ewing sarcoma family tumor (ESFT) patients who are nonmetastatic at presentation has improved considerably. The prognosis of patients with metastatic disease at the time of diagnosis and recurrence after therapy remains dismal. Drug-resistant disease at diagnosis or at relapse remains a major cause of mortality among patients diagnosed with ESFT. In order to improve the outcome for patients with potential relapse, there is an urgent need to find reliable markers that either predict tumor behaviour at diagnosis or identify therapeutic molecular targets at the time of recurrence. An improved understanding of the cell of origin and the molecular pathways that regulate tumorigenicity in ESFT should aid us in the search for novel therapies for ESFT. The purpose of this paper is thus to outline current concepts of sarcomagenesis in ESFT and to discuss ESFT patterns of differentiation and molecular markers that might affect prognosis or direct future therapeutic development.

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.

Pediatric rhabdomyosarcoma in Morocco

BACKGROUND

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in the first two decades of life. There is, however, a paucity of reports on the pattern of its occurrence in Africa. This study analyses the epidemiological pattern, clinical features, histology, and outcome in Moroccan children presenting with RMS.

METHODS

We retrospectively studied 100 consecutive cases of histologically proven RMS in previously untreated children <15 years old followed at the Pediatric Oncology Unit of the Children's Hospital of Rabat from January 1995 to December 2004.

RESULTS

RMS represented 5% of all the patients treated for cancer during this period. The male/female ratio was 2:1 with a mean age at diagnosis of 5 years. The embryonal subtype was the most frequent (73%) and the head and neck was the most common site of disease, followed by the genito-urinary tract and limbs. Chemotherapy was used in all patients; 44% also had a radical surgery and 23% radiation therapy. The event-free survival (EFS) at 10 years was 39% with relapse as the first cause of treatment failure. The overall survival at 10 years was 70%. The rate of treatment abandonment was 37%.

CONCLUSION

Epidemiology and clinical features of RMS in Moroccan children does not differ from others countries. However, EFS is lower than that reported elsewhere due to occasional lack of availability of drugs, inadequate local control, and abandonment.

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.

Rhabdomyosarcomas in adults and children: an update

CONTEXT

Rhabdomyosarcomas comprise a relatively common diagnostic entity among childhood cancers and a relatively rare one among adult tumors. They may possess a variety of histologies that generally differ among age groups. These lesions appear to be separate biologic entities as well as morphologic categories, with embryonal tumors having genetic lesions related to loss of heterozygosity and aberrant parental imprinting, alveolar tumors containing genetic fusions between PAX and forkhead genes, and pleomorphic tumors showing an accumulation of genetic lesions similar to other adult high-grade sarcomas.

OBJECTIVE

To present guidelines for diagnosis of rhabdomyosarcoma and recent finding concerning the biology and classification of these lesions.

DATA SOURCES

Review of recent and older published literature and distillation of the authors' experience.

CONCLUSIONS

Infants and young children tend to have embryonal rhabdomyosarcomas, adolescents and young adults tend to have alveolar rhabdomyosarcomas, and older adults tend to have pleomorphic rhabdomyosarcomas, although there is some overlap. Newer rare entities, including spindle cell rhabdomyosarcoma and sclerosing rhabdomyosarcoma, have been described in children and adults. Fusion-positive tumors have a distinct molecular signature with downstream activation of a number of myogenic and tumorigenic factors. Genetic testing may be successfully used for diagnosis and may guide therapy in future clinical trials. Differential diagnosis has become simpler than in previous years, because of use of myogenic factors in immunohistochemistry, but classification based solely on histologic features remains challenging.

Melanotic neuroectodermal tumor of infancy: clinical, radiological, and pathological features

We present a case of a 4-month-old female infant with a maxillary melanotic neuroectodermal tumor of infancy (MNTI) and review the pooled data from previous publications on this entity. The literature to date comprises 378 reported cases from 1918 to the present, from which data on the presence or absence of metastatic disease was available in 311, and on the presence or absence of local recurrence in 165. These pooled data suggest a local recurrence rate of 36% with metastasis occurring in 7% of cases. At present, the optimal management includes complete surgical excision with clear margins, but there are no reliable histopathological or molecular features to predict the biological behavior in individual cases.

Cyclophosphamide Dose Intensification during Induction Therapy for Intermediate-Risk Pediatric Rhabdomyosarcoma Is Feasible but Does Not Improve Outcome

PURPOSE

More than half of pediatric rhabdomyosarcoma cases have intermediate-risk features and suboptimal outcome (3-year failure-free survival estimates, 55 to 76%). Dose intensification of known active agents may improve outcome.

EXPERIMENTAL DESIGN

This pilot study evaluated the feasibility of dose intensification of cyclophosphamide in previously untreated patients ages < 21 years with intermediate-risk rhabdomyosarcoma. Induction therapy comprised four 3-week cycles of VAC: vincristine (V) 1.5 mg/m2 on days 0, 7, and 14; actinomycin D (A) 1.35 mg/m2 on day 0; and dose-intensified cyclophosphamide (C) on days 0, 1, and 2. The three cyclophosphamide dose levels tested were as follows: (a) 1.2 g/m2/dose; (b) 1.5 g/m2/dose; and (c) 1.8 g/m2/dose. Continuation therapy comprised nine additional cycles of VAC with 2.2 g/m2/cycle of C. Radiotherapy was administered at week 0 (parameningeal tumors with intracranial extension) or week 12 or 15 (all others).

RESULTS

Between October 1996 and August 1999, 115 eligible patients were enrolled. Three of 15 patients treated at dose level 2 experienced life-threatening dose-limiting toxicity (typhlitis +/- other severe toxicity). Dose level 1 was the maximum-tolerated dose, and 91 evaluable patients were treated at this level. The 3-year failure-free and overall survival estimates for patients treated at the maximum-tolerated dose were 52% (95% confidence interval, 41-64%) and 67% (95% confidence interval, 56-77%), respectively, at a median follow-up of 3 years.

CONCLUSIONS

A 64% increase in the standard cyclophosphamide dosage during induction (to 3.6 g/m2/cycle) was tolerated. However, outcomes were similar to those observed at lower dosages, suggesting that alkylator dose intensification does not benefit patients with intermediate-risk rhabdomyosarcoma.

Sclerosing rhabdomyosarcoma in childhood: case report and review of the literature

Rhabdomyosarcoma is the most common soft tissue malignancy in children but is rare in adults. The latest World Health Organization classification of soft tissue tumors recognizes embryonal, alveolar, and pleomorphic rhabdomyosarcomas. More recently, a sclerosing variant of rhabdomyosarcoma has been recognized and reported in seven adult patients. We describe a pediatric case of sclerosing rhabdomyosarcoma presenting as a sacral mass in a 3-year-old girl. Morphologically, the tumor showed a prominent sclerosing hyaline matrix and demonstrated pseudovascular and microalveolar architectural foci. Focal positivity was seen with desmin, smooth muscle actin, and myogenin. MyoD1 showed uniform diffuse nuclear staining. Fusion transcripts were not demonstrated by reverse transcriptase-polymerase chain reaction analysis. The histology, immunohistochemistry, and molecular genetics matched those reported in the seven adult cases of sclerosing rhabdomyosarcoma. This is the first case report, to our knowledge, of this rare tumor arising in the pediatric age group, and we compare the features with those reported in adult sclerosing rhabdomyosarcoma.

Malignant ectomesenchymoma of the orbit in a child: Case report and review of the literature

Malignant ectomesenchymoma is a rare soft tissue tumor of childhood composed of both mesenchymal and neuroectodermal elements. Reported sites of origin are head and neck, abdomen, perineum, scrotum, and extremities. A new case of an orbital ectomesenchymoma in a 7-year-old boy is presented. The clinical picture of the tumor, radiological findings, and its histopathologic and immunohistochemical characteristics are described. The patient was successfully treated with combined surgical resection and chemotherapy. All the other reported cases of malignant ectomesenchymoma with various sites of origin are also reviewed.

Risk assignment in pediatric soft-tissue sarcomas: an evolving molecular classification

Pediatric soft-tissue sarcomas are increasingly being defined by both histologic appearance and underlying chromosomal abnormalities to determine their biologic behavior. Most sarcomas of this type have specific chromosomal translocations that create unique fusion genes. Expression of such fusion genes may have diagnostic, prognostic, and surveillance implications for the patient. This review analyzes the fusion gene expressions seen with seven of the major types of pediatric soft-tissue tumors and their impact on biologic behavior. In nearly 50% of the malignancies discussed, the diagnostic, prognostic, and surveillance implications of their specific fusion gene expressions are already defined or becoming established (alveolar rhabdomyosarcoma, Ewing sarcoma/primitive neuroectodermal tumor, and synovial sarcoma). In the remainder of the tumors, these questions are rapidly being addressed. To facilitate future fusion gene studies, pediatric surgeons, pathologists, and oncologists need to work as a coordinated team to ensure proper tumor procurement. Large clinical cooperative trials involving biologic studies of pediatric soft-tissue sarcomas could facilitate advancement of knowledge in this area of pediatric oncology.