Malignant Ectomesenchymoma in Childhood

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.

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.

An Adult Paratesticular Malignant Ectomesenchymoma With Post-operative Flare-up of Lung Metastasis

Malignant ectomesenchymoma (MEM) which is derived from the remnants of migratory neural crest cells (ectomesenchyme) is a rare and rapidly progressing tumor consisting of neuroectodermal and mesenchymal neoplastic elements. This tumor occurs mostly in children and adolescents, but rarely in adults. We report a 34-year-old male with left paratesticular malignant ectomesenchymoma who received radical orchiectomy and was followed by post-operative flare-up of lung metastasis within 2 weeks. We present the overall treatment strategies for this extremely rare tumor and related findings.

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.

Malignant ectomesenchymoma: genetic profile reflects rhabdomyosarcomatous differentiation

Malignant ectomesenchymoma (MEM) represents a heterogeneous group of tumors, most likely originating from pluripotent primitive neural crest cells. In this report, we present an 8-month-old infant boy with an MEM on the left scrotum. Retrospective review of the incision biopsy showed the presence of a few ganglion cells in an otherwise classic embryonal rhabdomyosarcoma (RMS), whereas in the resection specimen after chemotherapy the combined RMS and ganglioneuroma components were very obvious. Cytogenetic analysis of the residual lesion showed an abnormal karyotype, 49, XY, +2, -6, +11, +20, +mar, with a hyperploidy in a subset of cells. By fluorescence in situ hybridization analysis, the marker chromosome was identified as originating from chromosome 6, and the tumor cells were negative for PAX3/PAX7 disrupting translocations specific for alveolar RMS. Gains of chromosomes 2, 11, and 20, found in the current case, are a common finding in embryonal RMS. These gains probably reflect the myogenic differentiation of MEM and support the genetic link between these 2 neoplasms. In addition to the conventional cytogenetics, array comparative genomic hybridization analysis was performed on the primary and residual tumors. The genomic profiles of both specimens were basically the same including the presence of 2 distinctive chromosome 6p21.32-p21.2 and 6p11.2 amplification regions in the primary tumor, which vanished in the postchemotherapy specimen. The pretreatment biopsy exhibited strong expression of HMGA1 and HMGA2 proteins in immunohistochemistry, with the shift toward the loss of expression of both genes in the posttreatment tumoral tissue. This finding supports the oncogenic properties of the HMGA family of proteins and their role in the process of malignant transformation.

Molecular array analyses of 51 pediatric tumors shows overlap between malignant intracranial ectomesenchymoma and MPNST but not medulloblastoma or atypical teratoid rhabdoid tumor

Gene microarray has been used to identify prognostic markers and genes of interest for therapeutic targets; a less common use is to show possible histogenetic relationships between rare tumor types and more common neoplasms. Intracranial malignant ectomesenchymoma (MEM) is a pediatric tumor postulated to arise from neural crest cells that contain divergent neuroectodermal and mesenchymal tissues, principally mature ganglion cells and rhabdomyosarcoma (RMS). We investigated a case of MEM by molecular, cytogenetic, and gene array analyses and compared results with our previously unpublished series of 51 pediatric tumors including conventional RMS, Ewing sarcoma (EWS), medulloblastoma (MED), atypical teratoid rhabdoid tumor (ATRT), and malignant peripheral nerve sheath tumor (MPNST); the latter is a sarcoma also with potential for divergent differentiation. Standard cytogenetic analyses and RT-PCR testing for the classic gene rearrangements seen in RMS [t(2;13)-PAX3/FKHR] and EWS ([t(11;22) & t(21;22)-EWS/FLI-1 & EWS/ERG), were used for characterization of the MEM, with gene expression microarray analyses on all tumor types. Gene rearrangement studies were negative in MEM. Gene expression microarray analyses showed tight clustering of the MEM with the MPNST (n = 2), but divergence from other pediatric tumors. MEM and MPNST both showed complex karyotypes, but without diagnostic translocations. Despite the presence of malignant skeletal muscle differentiation in the MEM, gene array testing showed no overlap with RMS, MED, or ATRT, but rather with MPNST. This suggests a common stem cell origin or embryonic gene recapitulation for these tumors and provides novel insights into their underlying biology.

Malignant ectomesenchymoma in the wrist of a child: case report and review of the literature

Malignant ectomesenchymomas, rare and potentially aggressive tumors, occur in children and exhibit mesenchymal and neuroectodermal components. This report describes the first patient diagnosed with a malignant ectomesenchymoma of the hand. The patient was a 17-month-old male who developed a hypothenar mass on his left hand that was surgically excised. Microscopic evaluation revealed ganglioneuroblastic, rhabdomyosarcomatous, and chondrosarcomatous elements. Following excisional biopsy he was treated with cyclophosphamide, doxorubicin, vincristine, ifosfamide, and etoposide. After 3 courses of chemotherapy the patient had a wide reexcision with no residual tumor. The patient is 4 years from diagnosis, without evidence of disease.

Divergent differentiation in malignant soft tissue neoplasms: the paradigm of liposarcoma and malignant peripheral nerve sheath tumor

In tumors clonality does not always translate into morphologic uniformity. While most sarcomas exhibit only one line of histologic differentiation, a minority may display a strikingly diverse phenotype in addition to the main lineage. This phenomenon not only presents a diagnostic problem but also raises questions about the commitment of tumor cells toward a specific phenotype. Among sarcomas, malignant peripheral nerve sheath tumor (MPNST) and dedifferentiated liposarcoma are two entities in which divergent differentiation is a relatively frequent event. Diagnostically it is crucial to recognize the "primary" sarcoma in such tumors correctly and distinguish it from the "secondary" divergent elements. The presence of the latter could be the first morphologic clue to a specific sarcoma type. Even though it may be difficult to explain the pathogenesis of divergent differentiation, divergence still illustrates that the phenotype of a tumor cell is not set in stone but can be modulated or switched by a number of factors.

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

Ectomesenchymomas (EM) are rare malignant neoplasms usually consisting of rhabdomyosarcoma (RMS) with a neural component. Only 21 cases have been previously reported. Here we extend the clinicopathologic spectrum of EM by describing our findings in 15 cases. Only 5 patients were infants; 10 were < or =3 years old and 5 were > or =6 years old. No male predilection was observed; 7 were female. The originating institutional diagnoses were; RMS (12), undifferentiated sarcoma (1), or EM (2), suggesting underdiagnosis of this entity. The primary tumor sites included external genital (5), pelvis/abdomen (6), head and neck (3), and extremity (1). The size of the primary neoplasm was usually > or =5 cm at diagnosis but dissemination only occurred in a minority. Local infiltration was not uncommon. These neoplasms were typically multilobate, thinly encapsulated, hemorrhagic, and necrotic. Light microscopic features were highly variable, but embryonal RMS with scattered or clustered ganglion cells, often in lacunae, was characteristic. In some cases, primitive neuroblastic or neuroectodermal areas were found and/or a component of alveolar RMS was seen. Focal anaplasia was occasionally observed. Mitotic activity appears higher than previously appreciated and some necrosis was invariably present. Electron microscopy was performed in 11 cases, which confirmed skeletal muscle +/- neural differentiation. Cytogenetic studies performed in five cases revealed no specific abnormality. Monoclonal neuron-specific enolase was the best marker of ganglion cells and primitive neural elements. MIC-2 (CD99) membrane expression was not definitively present in any of the six cases examined. A number of the above parameters appear to be of some prognostic significance, but overall, these neoplasms appear to have a similar outcome as would be predicted for their RMS element alone (exclusive of any neural component), with respect to the RMS subtype, age of the patient, and anatomic location of the neoplasm.

Rhabdomyosarcoma metastasizing as a malignant ectomesenchymoma

Rhabdomyosarcoma is a common childhood malignancy that may occasionally occur as a component of a mixed mesenchymal tumor, e.g., a triton tumor or malignant ectomesenchymoma. A case is reported of a 13-year-old boy who had resection of a paratesticular embryonal rhabdomyosarcoma with subsequent radiation and chemotherapy. Two years later, a retroperitoneal metastasis was resected. Histology showed a mixture of rhabdomyoblasts, ganglion cells, and a third population of cells with combined features of these two distinct cell types. Electron microscopy confirmed the presence of rhabdomyoblasts with characteristic bundles of myofilaments and Z-band material, and ganglion cells with prominent nuclei and nucleoli, rough endoplasmic reticulum, dense core granules, filaments, and tubules. Notably, the third cell population showed features of both rhabdomyoblasts and ganglion cells. Immunohistochemistry confirmed the mixed population of rhabdomyoblasts (positive for vimentin, desmin, negative for S-100, NSE), ganglion cells (positive for S-100 and NSE, negative for vimentin and desmin), and the third population expressing all test antigens. The features of this metastatic lesion are those of a malignant ectomesenchymoma with combined rhabdomyosarcoma and ganglioneuroma components. It is postulated that this lesion results from biphenotypic expression of tumor cells that previously expressed only rhabdomyoblastic differentiation. The role of prior chemotherapy and radiotherapy in this particular case is unclear.