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Peripheral neuroectodermal tumors are uncommon cancers arising from outside the central nervous system. The urinary system is rarely involved. The differentiation of these tumors from other small cell cancer and neuroblastoma is based on immunohistochemical differences. We report 2 cases of such tumors arising from the renal parenchyma. Tumor behavior and treatment modalities are discussed.
Synovial sarcoma is a relatively common sarcoma in adults, which in its classic bimorphic form infrequently poses a diagnostic problem. Monomorphic spindled variants, as well as the less common poorly differentiated variants, may be confused with other soft-tissue sarcomas; the poorly differentiated variant (PDSS), in particular, may be histologically indistinguishable from other small, blue, round cell tumors, including primitive neuroectodermal tumors (PNETs). Detection of the synovial sarcoma-associated t(X;18) by either cytogenetic or molecular genetic approaches may be necessary to confirm the diagnosis of synovial sarcoma in difficult cases. We evaluated 10 cases of PDSS from eight patients using a panel of antibodies (including those to intermediate filament proteins, nerve-sheath associated markers, and neuronal and neuroectodermal associated markers) in order to better establish the immunophenotype of this tumor and to help distinguish it from the tumors with which it may be confused, particularly PNETs and high-grade malignant peripheral nerve sheath tumors (MPNSTs). Our results showed PDSS to have significant immunophenotypic overlap with both PNETs and MPNSTs. In most instances these three entities may be differentiated by a panel of antibodies that should include those to both low and high molecular weight cytokeratins, epithelial membrane antigen, type IV collagen, CD99, CD56, and S-100 protein. Our results also suggest that synovial sarcoma may be a tumor showing combined neuroectodermal and nerve sheath differentiation--perhaps because of translocation-associated expression of specific proteins--rather than a carcinosarcoma of soft tissues or a tumor of specialized arthrogenous mesenchyme.
Ewing's sarcoma and the related primitive neuroectodermal tumor (PNET) share a unique and specific t(11;22)(q24;q12) chromosomal translocation. The breakpoints have recently been cloned and shown to involve the EWS gene on chromosome 22 and the FLI-1 gene on chromosome 11. Translocation results in the fusion of these genes on the der(22) chromosome, resulting in the production of a novel chimeric EWS/FLI-1 message. Using oligonucleotide primers derived from EWS and FLI-1 complementary DNAs, we were able to amplify a specific fusion transcript from 18 of 18 cases containing t(11;22) and 10 of 14 cases of Ewing's sarcoma/PNET that had unsuccessful cytogenetics. No EWS/FLI-1 fusion transcripts were detected in five cell lines derived from cases of pediatric sarcomas having a histological diagnosis other than Ewing's sarcoma/PNET. The sensitivity and specificity of this PCR analysis demonstrates the usefulness of this approach for the primary diagnosis of t(11;22)-containing Ewing's sarcoma/PNET and for the detection of metastatic or residual disease.
Despite the phenotypic similarities between primitive neuroectodermal tumors of the central nervous system, childhood neuroblastoma, and peripheral neuroepithelioma, a histogenetic relationship among these neoplasms has not been shown. High levels of N-myc expression occur selectively in developing brain and in some embryonic tumors of neural origin. N-myc amplification and high levels of N-myc expression in childhood neuroblastoma have been correlated with disease stage and prognosis. To determine whether the copy number of the N-myc gene in primitive neuroectodermal tumors of the central nervous system is altered, we examined 20 primitive neuroectodermal tumors by Southern and/or slot blot hybridization to a 1-kilobase N-myc genomic DNA sequence and a 492-base pair N-myc-specific subclone as well as to a 1.1-kilobase albumin complementary DNA sequence as a control for gene copy number. Amplification of the N-myc gene was detected in two cerebellar tumors both of which exhibited neuronal differentiation by light microscopy. These tumors had not been treated previously. Of the remaining 18 tumors, eight were undifferentiated, three showed early neuroblastic, and seven focal glial differentiation. These findings suggest a possible relationship between N-myc amplification and neuronal differentiation.
The term "small round-cell tumor" describes a group of highly aggressive malignant tumors composed of relatively small and monotonous undifferentiated cells with high nuclear to cytoplasmic ratios. This group includes Ewing's sarcoma (ES), peripheral neuroepithelioma (aka, primitive neuroectodermal tumor or extraskeletal ES), peripheral neuroblastoma ("classic-type"), rhabdomyosarcoma, desmoplastic small round-cell tumor, lymphoma, leukemia, small-cell osteosarcoma, small-cell carcinoma (either undifferentiated or neuroendocrine), olfactory neuroblastoma, cutaneous neuroendocrine carcinoma (aka, Merkel-cell carcinoma), small-cell melanoma, and mesenchymal chondrosarcoma. Their clinical presentations often overlap, thus making a definitive diagnosis problematic in some cases. Yet, a clear understanding of their clinicopathologic features usually allows for a confident diagnosis, especially if immunohistochemistry is used. The following is a review of the immunohistochemistry of this small round-cell tumor group.
Peripheral neuroepithelioma of soft tissue is a malignant primitive neuroectodermal tumor that appears both in children and adults and usually has a poor outcome. Fine needle aspiration on two patients with tumors in the lower limbs showed small round cells with unipolar processes and a tendency to form Homer-Wright rosettes. The cells had a round to oval nucleus with fine chromatin, up to four small, conspicuous nucleoli and vacuolated, periodic acid-Schiff-positive cytoplasm. The diagnosis was supported by electron microscopic study of the aspirate, which showed features of neuroblastic differentiation (i.e., neurosecretory granules), and by histologic, immunohistochemical and cytogenetic study of the resected tumors.
Ewing's sarcoma of bone (ESB) and peripheral neuroepithelioma (PN) are frequently considered to be different tumors. Some researchers have suggested that PN is morphologically a neuroectodermal Ewing's sarcoma. We sought to determine the extent of neuroectodermal features in conventional ESB on direct patient material (25 cases) and to compare these tumors with a similar group of readily diagnosed PNs (10 cases). Light microscopic, ultrastructural, and immunophenotypic parameters were assessed and compared for both groups. The avidin-biotin complex method was used. All tumors were antigenically intact since all stained for vimentin or at least one marker. Neuroectodermal antigens (neuron-specific enolase, Leu-7 [HNK-1], neurofilament 200 kd, and S100) were found in nine of 10 cases of PN and in 17 of 25 cases of ESB. In ESB, an atypical light microscopic appearance correlated with the presence of neuroectodermal features in most cases, but neuroectodermal phenotype was more frequent (68%) than morphological evidence of neuroectodermal differentiation (36%). These data support the concept that ESB and PN are both peripheral primitive neuroectodermal neoplasms, differing only in extent of neuroectodermal phenotype and morphological differentiation.
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FLI1 (Friend leukemia virus integration 1), a member of the Ets gene family, is disrupted on 11q24 by the Ewing's Sarcoma (ES) and Peripheral Neuroepithelioma (PNE) t(11;22)(q24;q12) translocation. ES and PNE are Primitive Neuroectodermal Tumors (PNETs) and the consistent translocation t(11;22)(q24;q12) can be used for differential diagnosis. In PNETs the 3' part of human FLI1 is translocated from 11q24 to 22q12, where it is juxtaposed to the 5' end of the Ewing's Sarcoma gene (EWS). A fusion transcript, resulting in a chimeric protein, is generated. Here, we present the isolation and detailed characterization of a 250-kb colinear YAC, B45C11, which encompasses the ES and PNE breakpoint on 11q24, as shown by FISSH on ES and PNE chromosomes and interphase nuclei. This YAC represents a new reagent for potential use in rapid differential diagnosis by FISSH on tumor biopsies and on paraffin embedded samples, particularly when DNA and/or RNA are not available for molecular analysis. YAC B45C11, which spans 250 kb of contiguous DNA around the ES and PNE breakpoint, contains the entire FLI1 gene. Three potential HpaII-tiny-fragment (HTF) islands are revealed within the YAC. One of these islands appears to be associated with the 5' end of FLI1, which extends over approximately 120 kb of DNA on 11q24. In addition, we demonstrate that YAC B45C11 contains other transcribed sequences in addition to FLI1, by "cross-species" Northern blot hybridizations, which suggests the presence of additional genes in the immediate vicinity of the ES breakpoint on 11q24.
Peripheral malignant neuroectodermal tumors are rare and aggressive small-cell tumors seen predominantly in children and young adults. Mediastinal location is very uncommon. A mediastinal primitive neuroectodermal tumor was diagnosed in a 27-year-old man. Despite treatment combining surgery, radiotherapy and chemotherapy, disease recurred locally along with lungs, spinal and epidural metastases, leading to death. CT and MRI examinations show heterogeneous masses with necrosis, hemorrhage and intense enhancement after Gadolinium injection. The CT and MRI findings are not specific and the diagnosis is based on pathologic, immunohistochemical and electron microscopic features. Although uncommon, peripheral neuroectodermal tumor should be considered in the differential diagnosis of posterior mediastinal masses in children and young adults.
Primitive neuroectodermal tumor (neuroepithelioma) is a relatively common central nervous system tumor in children. Those arising from a peripheral nerve are extremely rare in childhood. There is only one reported case in 6-year-old where the tumor arose from the sciatic nerve. A case of neuroectodermal tumor of the chest wall, arising from the intercostal nerve, in a newborn is presented. The tumor metastasized to the brain. Prominent Homer-Wright rosettes, with central eosinophilic fibrillar substance similar to that seen in neuroepithelioma of the central nervous system, were present in the primary tumor and brain metastases. Ultrastructure, as revealed by transmission electron microscopy, is also described.
We describe a 4-yr-old boy with an occult primitive neuroectodermal tumor, who suffered fatal PTE after a second course of HDC with autologous PBSCT. On day + 52 after a second PBSCT, he was admitted because of respiratory distress. Respiratory failure rapidly progressed and he died within 4 days. The diagnosis of PTE was confirmed by a lung perfusion study with technetium-99m macroaggregated albumin, but too late to allow treatment. Although rare, PTE must be recognized as an important differential diagnosis when respiratory symptoms are observed after HDC with PBSCT.
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The differential diagnoses of childhood and adolescent tumors composed of small round cells include a distinctive clinicopathological entity called malignant small cell tumor (MSCT) of the thoracopulmonary region in childhood. In the present study, 15 such tumors that fulfilled the criteria by Askin et al. were examined for features of possible neural differentiation by light and electron microscopy (EM). With hematoxylin-eosin stain (H&E) the tumors were made up of small undifferentiated cells; rosette formation was noticed in four cases. By immunohistochemistry all 15 tumors were positive for neuron/specific enolase (NSE), which is a specific marker for neural elements and their tumors including neuroblastomas. Ten of 15 MSCT had positive PAS staining. Ultrastructurally dense core (neurosecretory) granules and cell processes indicative of neuronal differentiation could be recognized in 10 of 14 tumors. The dense core granules were often atypical. Filamentous cytoskeleton, never observed in Ewing's sarcoma, was often present. Based on the current results, MSCT of the thoracopulmonary region can be considered a peripheral neuroectodermal tumor with the possible origin in intercostal nerves. MSCTs are generally misdiagnosed as Ewing's sarcoma due to their primitive appearance in H&E sections and their periodic acid-Schiff positivity. NSE immunostaining, preferably augmented by electron microscopy, is necessary for their correct diagnosis.
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Primitive neuroectodermal tumors are rare, highly aggressive neoplasms that affect both sexes and occur in all age groups. They are a large group of neoplasms with neuroepithelial differentiation, including cutaneous neuroblastomas. Histopathologically they are characterized by a rather uniform population of small, dark cells, with or without Homer Wright rosettes. Immunohistochemically they stain for one or more of the reputed neural markers. Ultrastructurally they show interdigitating processes containing neurosecretory granules, intermediate filaments, and microtubules. We describe a patient with unusual multiple peripheral neuroectodermal tumors localized to the skin, with benign biologic behavior. The patient related the appearance of new lesions for several years without evidence of visceral dissemination or systemic complications. The histopathologic, immunohistochemical, and ultrastructural findings support the diagnosis of a peripheral neuroectodermal tumor.
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