Malignant peripheral neuroectodermal tumours of bone other than Askin's neoplasm: characterization of 14 new cases with immunohistochemistry and electron microscopy

Primitive Neuroectodermal Tumor/Ewing Sarcoma of the Retina

An 11-year-old boy underwent enucleation of his left eye for an intraocular tumor. Examination showed a small, round blue cell tumor arising in the peripheral retina near the ciliary body. Immunohistochemical stain results were positive for neuron-specific enolase, synaptophysin, cluster of differentiation 99 (CD99), Friend leukemia integration 1, and CD56. Ultrastructural findings included occasional intracytoplasmic dense core granules. Polymerase chain reaction of the tumor showed a Ewing sarcoma/Friend leukemia integration gene fusion product. The tumor was classified as a primitive neuroectodermal tumor/Ewing sarcoma of the retina and should be distinguished from retinoblastoma. To our knowledge, this is the first case of primary primitive neuroectodermal tumor of the retina.

Peripheral primitive neuroectodermal tumor of the small bowel mesentery: a case showing perforation at onset

A case of peripheral primitive neuroectodermal tumor of the small bowel mesentery with an uncommon clinical onset is reported. A 40-year-old man was admitted to hospital because of acute severe abdominal pain. Chest X-ray revealed a free air sign beneath the diaphragm. At emergency surgery a mass measuring 11.0 x 8.0 cm with perforation was located in the jejunal mesenteric region. Histologically the resected lesion consisted of sheets of undifferentiated small round cells forming abortive Homer Wright rosettes. Some spindle-shaped cells showed perivascular pseudorosettes. Immunohistochemical study revealed that the tumor cells expressed positivity against CD99 (MIC2), neuron-specific enolase, synaptophysin and vimentin. To the authors' knowledge this is the first documentation of peripheral primitive neuroectodermal tumor of the small bowel mesentery with perforation at onset.

Neoadjuvant chemotherapy for peripheral malignant neuroectodermal tumor of bone: recent experience at the istituto rizzoli

PURPOSE

The results achieved in 44 patients with nonmetastatic peripheral neuroectodermal tumor (PNET) of bone treated with neoadjuvant chemotherapy are reported.

PATIENTS AND METHODS

A six-drug regimen of chemotherapy (vincristine, doxorubicin, dactinomycin, cyclophosphamide, ifosfamide, and etoposide) was administered to all patients. Local treatment consisted of surgery in 20 patients, surgery followed by radiotherapy in 13, and radiotherapy only in 11.

RESULTS

At a mean follow-up of 4.5 years (range, 2 to 7 years), 23 patients (52%) remain event-free, 20 have relapsed (45%), and one has died of chemotherapy-related toxicity. The 5-year event-free survival and overall survival were 54.2% and 62.7%, respectively. To assess the prognostic significance of neural differentiation in the family of Ewing's sarcoma, these results have been compared with the outcomes of 138 concomitant patients with typical Ewing's sarcoma (TES) who were treated according to the same protocol. Of these, 103 (75%) remained continuously event-free, 34 (24%) relapsed, and one died of chemotherapy-related toxicity. It follows that PNET patients treated with this chemotherapy regimen have a significantly worse prognosis than typical ES patients (5-year event-free survival, 54.2% v 70.6%, P <.012; 5-year overall survival, 62.7% v 78.3%, P <.002).

CONCLUSION

The authors conclude that studies into new adjuvant therapy for Ewing's sarcoma modulated according to risk of relapse should also consider neural differentiation as a risk factor.

Neuroectodermal differentiation in Ewing's sarcoma family of tumors does not predict tumor behavior

The observation that neuroectodermal differentiation imparts a worse prognosis to the Ewing family of tumors has been suggested by some studies and refuted by others. To assess whether the diagnosis of Ewing's sarcoma versus peripheral primitive neuroectodermal tumor (PNET) affects prognosis, we analyzed tumors from 63 analogously treated pediatric and young adult patients from the National Cancer Institute and St Jude Children's Research Hospital and retrospectively compared the results with clinical outcomes. The tumors were assessed using standard light microscopy and immunohistochemical stains for neuron-specific enolase, CD57, S100 protein, neurofilament protein, and synaptophysin with or without antigen retrieval. Ultrastructural evaluation was also performed in 39 tumors. Classification was performed using Kiel criteria as well as a modified classification. Kaplan-Meier analyses, with Mantel-Haenzel evaluation of the significance of the differences, were performed separately for localized or metastatic tumors. Using the Kiel classification on a subset of 60 cases, 39 tumors qualified as PNET and 21 as Ewing's sarcoma. Using the modified classification on a subset of 61 cases, 14 were classified as PNET, 21 as atypical Ewing's sarcoma, and 26 as Ewing's sarcoma. The addition of electron microscopy to the diagnostic armamentarium significantly increased the likelihood of identifying PNET. No significant differences in event-free or overall survival were seen using either the modified or Kiel classification, regardless of the ancillary diagnostic techniques employed. In this exploratory analysis, neuroectodermal differentiation did not play a role in clinical outcome. Confirmation of this finding will require a larger, separate study of similarly treated patients, and it may not apply to older patients.

Cervical cord compression due to atypical primary neuroectodermal tumor (PNET): one-stage removal and combined cervical spine stabilization. Case report

INTRODUCTION

The neuroectodermal tumor of bone constitutes a recently isolated neoplasm, which morphologically resembles the peripheral neuroepithelioma of soft tissue. The diagnosis is made by excluding readily classified small round cell neoplasms and then demonstrating the neural origin of the tumor by means of ultrastructural or immunocytochemical studies.

CLINICAL CASE

We report a case of a primary neuroectodermal tumor (PNET) with atypical findings (primary cervical location, massive vertebral body infiltration and isolated neurological symptomatology). Total tumor removal was achieved by means of a one-stage three-level laminectomy (partial C5, total C6-C7), C6 somatectomy, and combined anterior and posterior cervical spinal instrumentation and fusion.

CONCLUSIONS

Our case presents three peculiar features: 1) isolated myelopathic symptomatology (first case described); 2) primary isolated massive vertebral cervical involvement with intraspinal epidural extension (first case described); 3) one-stage tumor resection, fusion and instrumentation. Since radiation therapy causes tumor shrinkage but is not curative, radical removal is mandatory even with complex instrumentation procedures.

Cytologic characteristics of peripheral neuroectodermal tumors in fine-needle aspiration smears: a retrospective study of three pediatric cases

Cytologic diagnosis of peripheral neuroectodermal tumors (PNT) on fine-needle aspiration (FNA) smears represents a challenge to the cytopathologist. Usually ancillary studies are used to achieve definitive diagnosis. We retrospectively examined FNA material from three cases of PNT with the aim of identifying their features. Positive and negative cytologic findings were recognized. Positive features for PNT included the presence of: rather uniform appearance of the cells, which display scant but almost always-present perinuclear clear cytoplasm (suggesting a bland epithelial tumor); nuclei with distinctively smooth nuclear membrane contour, finely granular chromatin, and one or two small nucleoli (suggesting neuroendocrine anlage); and organization of the cells singly or in cohesive clusters. Negative findings included the absence of: frequent mitotic figures, large nucleoli, nuclear pleomorphism, cellular debris, histiocytes, and polymorphonuclear leucocytes. The smears appeared clean, with small, uniform cells having features suggesting a neuroendocrine epithelial tumor. These findings may prove useful for accurate cytologic diagnosis and differentiation of PNT from other small blue round cell tumours (SBRCT) of soft tissues without the use of ancillary studies since, when properly evaluated, cytomorphology of the latter group of tumors is more heterogeneous than generally believed.

Neurogenic potential of Ewing's sarcoma cells

We investigated the capacity of eight well-characterized Ewing's sarcoma cell lines to differentiate towards a neural phenotype. Ewing's sarcoma cells expressed the neuroectoderm-associated antigens such as nerve growth factor (NGF) receptor, N-CAM (6H7 and Leu-19) and Leu-7. Ewing's sarcoma cells also exhibited the potential for neural differentiation at the mRNA level; neuron-specific medium- and low-sized filament (NF-M and NF-L) expression was induced by dibutyryladenosine cyclic monophosphate. The pattern of expression of NF-L obtained by using alternative polyadenylation sites in Ewing's sarcoma cells differed from that in peripheral primitive neuroectodermal tumour (PNET) cells, and was similar to that in undifferentiated neural tissues. Furthermore, the NGF receptors detected by immunohistochemistry were found to be non-functional as assayed by c-fos induction with NGF treatment. The results indicate that Ewing's sarcoma cells maintain a primitive phenotype and have the potential to differentiate into a neural phenotype, indicating that Ewing's sarcoma is distinct from PNET.

Is neuro-ectodermal differentiation of Ewing's sarcoma of bone associated with an unfavourable prognosis?

Among Ewing's sarcoma (ES) of bone and related entities are tumours with neuro-ectodermal features that could represent a biologically distinct type. In order to assess the prognostic significance of the various forms of ES, a retrospective joint study involving three cancer centres in Europe and the U.S.A. was initiated. The material from 315 primary ES was reviewed by a panel of five pathologists and classified as typical ES (220 cases), atypical ES (48 cases) or ES with neuro-ectodermal features (47 cases). Prognostic factor analysis on treatment failure-free survival was performed using the Cox model. It included histopathological classification, initial patient characteristics, clinical presentation and treatment type. After multivariate analysis, in addition to treatment type (P < 0.001), metastases (P = 0.003) and proximal tumour location (P = 0.006), two histopathological parameters correlated with poor treatment failure-free survival, the presence of filigree pattern (P = 0.044) and dark cells (P = 0.043). We conclude that ES with neuro-ectodermal features does not appear to have a different outcome to the other subtypes.

Patterns of differentiation in extraosseous Ewing's sarcoma cells. An in vitro study

BACKGROUND

In vitro, tissue culture-associated differentiation assays have facilitated the identification of multiple tumor-cell types.

METHODS

We have investigated the capability of differentiation of three extraosseous Ewing's sarcoma cell lines toward a neural and muscular direction by in vitro stimulation with dibutyryl cyclic adenosine-monophosphate (db cAMP) and 5-azacytidine, respectively.

RESULTS

Elongation of cytoplasmic processes and increase of neural markers chromogranin, S-100 protein, and glial fibrillary acidic protein were observed after db cAMP treatment of these lines and neurosecretory granules as well as myelin figures were demonstrated ultrastructurally. These results support the existence of several pathways of neural differentiation in vitro--neuroblastic, Schwannian, and central glial--in stages of maturation more advanced than those previously reported in Ewing's sarcoma of bone. The cell lines showed no definitive myoblastic differentiation after 5-azacytidine treatment.

CONCLUSIONS

These data suggest that these three extraosseous Ewing's sarcoma cell lines configurate a heterogeneous group of tumors with respect to capability of differentiation into the neural lineage, arrested at more advanced stages of neural crest development than Ewing's sarcoma of bone and without capability of myoblastic differentiation with 5-azacytidine.

Small cell osteosarcoma of bone: an immunohistochemical study with differential diagnostic considerations

Seventy-nine cases of small round cell tumors involving bone were studied in an attempt to learn whether the immunohistochemical features of the lesions might allow distinction of small cell osteosarcoma from other potential differential diagnostic considerations, including Ewing's sarcoma, atypical Ewing's sarcoma, primitive neuroectodermal tumor, mesenchymal chondrosarcoma, lymphoma, and the Askin tumor. The tissues studied were all formalin-fixed, decalcified, paraffin sections from patients between the ages of 16 and 48 years. With one exception (a small cell osteosarcoma), none of the lesions was cytokeratin positive. Moreover, none of the lesions was epithelial membrane antigen, desmin, factor VIII-related antigen, synaptophysin, or Leu-M1 positive. Accordingly, strong positivity for these antibodies in a majority of tumor cells should prompt inclusion of tumor types other than those listed above in the differential diagnosis. Vimentin positivity was seen in a majority of the tumors studied irrespective of histologic type. Scattered tumor cells (< 25%) showed positivity with antibodies to muscle-specific actin and smooth muscle actin in several of the different tumor types studied. No lesions other than lymphoma were leukocyte-common antigen (LCA) positive; all but two lymphomas were LCA positive, while all but one lymphoma were L26 positive. One (lymphoblastic) lymphoma was LCA and L26 negative. S-100, neuron-specific enolase, and Leu-7 did not prove to be specific for "neural-associated" tumors, but rather appeared in some small cell osteosarcomas, Ewing's sarcomas, atypical Ewing's sarcomas, primitive neuroectodermal tumors, mesenchymal chondrosarcomas, lymphomas, and Askin tumors. Antibody to cell surface antigen HBA71 was positive in three Ewing's sarcomas (two typical and one atypical) and negative in small cell osteosarcoma (three cases), mesenchymal chondrosarcoma (two cases), and lymphoma (one case). While some guidance may be derived from analysis of immunohistochemical staining patterns in a given lesion, the results reported in the present study do not suggest that routine immunohistochemistry alone will permit distinction of these small cell tumors of bone from one another. The value of immunohistochemical studies appears to lie particularly in the use of antibodies to LCA and S-100 protein to distinguish lymphoma and mesenchymal chondrosarcoma, and perhaps antibody to HBA71 to distinguish neural family lesions (such as Ewing's sarcoma), from other small cell tumors, such as small cell osteosarcoma.

Cytogenetics of Askin's tumour. Case report and review of the literature

The eleventh cytogenetically analyzed Askin's tumour, diagnosed in a two-year-old girl, is reported. Chromosomal analysis revealed a pseudodiploid karyotype of tumour cells with translocations of t(11;22)(q24;q12) and der(4)t(2;4)(q24;q35). The observed t(11;22)(q24;q12) is not only a unique characteristic of all cytogenetically analyzed Askin's tumours but it also occurs in 92-100% of peripheral neuroepithelioma and of Ewing's sarcoma, irrespective of its osseous or extraosseous localization. This genetical similarity further supports a nosological concept according to which Askin's tumour, Ewing's sarcoma and peripheral neuroepithelioma represent phenotypic variations of the same tumour, namely the peripheral primitive neuroectodermal tumour.

The immunophenotype of Ewing's sarcoma. An immunohistochemical analysis

Since 1963, 53 cases of Ewing's sarcoma have been diagnosed at the N. Goormaghtigh Institute of Pathological Anatomy. All tumours were classified according to their growth pattern as described by Kissane: diffuse, lobular or organoid, the latter with pseudorosettes, or belonging to the fillagree type. In 45 cases, an immunohistochemical examination was carried out on routinely processed material in order to determine the immunophenotype of the tumours and to get more information on the histogenesis of the tumours. Antibodies against cytokeratin, desmin, vimentin, neurofilaments, neuron-specific enolase, Leu7, synaptophysin, chromogranin, the muscle-specific actin, the Von Willebrand factor and the common leucocyte antigen were used in a biotin-streptavidin procedure. The presence of neural markers such as neuron-specific enolase, synaptophysin and Leu7 was proved in the majority of the cases. The expression of the three markers was absent in only two cases. Neurofilaments were demonstrated to be present in 5 of the 6 cases for which fresh material was available. The results of this study point towards a possible neuroectodermal origin of Ewing's sarcoma. This is in agreement with the results of cell culture experiments and of cytogenetic studies.

Differential expression of leukocyte differentiation antigens in small round blue cell sarcomas

BACKGROUND

Small round blue cell sarcomas (SRBCS) comprise a group of cytomorphologically poorly differentiated neoplasms that are characterized by different histogenesis and biologic behavior.

METHODS

Twenty-seven well-characterized SRBCS were examined immunohistochemically to detect the expression of a panel of leukocyte differentiation (CD) antigens and class I (HLA-A,B,C) and class II (HLA-DR) major histocompatibility complex antigen.

RESULTS

Although various cell surface antigens were detectable in SRBCS, the pan-leukocytic-histiocytic CD53 antigen was absent in the neoplastic population of all tumors studied; this finding allowed the authors to discriminate these lesions from lymphomas and leukemias. Some antigens had a differential pattern of expression in the SRBCS group, in particular in the undifferentiated tumor cell populations. In most instances, neuroblastomas (NB) and ganglioneuroblastomas (GNB) were CD9+/CD24+/CD56+ but CD40-/HLA-A,B,C-. Rhabdomyosarcomas (RMS) were CD56+ in all specimens and CD9+ in many samples; generally, they showed CD24-/CD40-/HLA-A,B,C-. Ewing sarcomas (ES) and peripheral primitive neuroectodermal tumors (pPNET) were HLA-A,B,C+/CD40+ but CD9-/CD24-/CD56- in most instances. Thus, with few exceptions, the expression of CD9 and CD56 and the simultaneous absence of HLA-A,B,C and CD40 differentiated GNB, NB, and RMS from ES and pPNET. GNB, NB, and RMS differed in regard to their CD24 expression.

CONCLUSIONS

These data show that various types of SRBCS have different patterns of cell surface antigens. Therefore, these antigens are considered to be helpful in the immunophenotypic subclassification of SRBCS: The immunophenotypic similarities between ES and pPNET, however, might be an additional argument for a close relationship between these two lesions.

Does malignant small round cell tumor of the thoracopulmonary region (Askin tumor) constitute a clinicopathologic entity? An analysis of 30 cases with immunohistochemical and electron-microscopic support treated at the Institute Gustave Roussy

The morphology and clinical outcome of 30 patients with malignant small round cell tumors located in the thoracopulmonary region (Askin tumor) are reported. Histologically, all tumors had similar patterns, with small round-to-oval cells and a lobulated stroma. Immunohistochemical analysis always resulted in positive staining for one or several neural markers. No significant differences were found compared with the immunomarkers in 26 typical Ewing's sarcomas located outside the thoracic wall. In three specimens, electron microscopy confirmed the presence of membrane-bound neurosecretory granules. It was confirmed that there is a remarkable similarity among all malignant small round cell tumors, including Askin tumor and Ewing's sarcoma. Overall survival was poor with a 2-year rate of 38% and a 6-year rate of 14%.

A case of small round cell tumor of the thoracopulmonary region with myogenic and neurogenic elements

We here report a unique case of a young boy with an intrathoracic tumor which consisted of neurogenic and myogenic elements. The initial pathological diagnosis was alveolar rhabdomyosarcoma. The tumor tissue from surgical resection was composed of three parts, each showing a different histological appearance, i.e. a monotonous small cell area, an alveolar area, and an area consisting of pleomorphic rhabdomyoblasts. The small round cells in the monotonous area were immunoreactive with the antibodies for Leu7, neuron-specific enolase (NSE), neurofilament proteins (NFP), and beta 2 microglobulin, but not with the antibody for desmin. These cells also had dense core granules. The tumor cells in the alveolar area were immunoreactive with the antibodies for Leu7 and desmin, but not with the antibody for NFP. Pleomorphic rhabdomyoblasts were immunoreactive with the antibody for desmin, but not with the antibodies for Leu7 and NFP. These findings imply that this tumor consisted of neurogenic and myogenic elements and is considered to be a special type of rhabdomyosarcoma.

Malignant peripheral neuroectodermal tumor and its necessary distinction from Ewing's sarcoma. A report from the Kiel Pediatric Tumor Registry

A new classification scheme is proposed for the differential diagnosis of Ewing's sarcoma and malignant peripheral neuroectodermal tumor (MPNT) based on conventional light microscopic and immunohistochemical findings. The presence of Homer-Wright rosettes and/or the expression of at least two neural markers is diagnostic of MPNT Ewing's sarcoma. Ewing's sarcoma was diagnosed in cases lacking Homer-Wright rosettes and expressing no neural marker or only one in immunohistochemistry. Using this "new" approach considerable differences were found between both tumor types. Although most MPNT were located in the thoracopulmonary region, Ewing's sarcoma was located predominantly in the pelvis and extremities. The mean age of MPNT patients was greater than that of Ewing's sarcoma patients. Most importantly, however, was a statistically significant difference in prognosis: disease-free survival in Ewing's sarcoma patients at 7.5 years follow-up was 60% compared with 45% MPNT patients (P = 0.026). The detection of HNK-1 in MPNT indicated a more aggressive biologic behavior, and the expression of protein S-100 appeared to be correlated with a more favorable clinical course.

Towards the phenotyping of soft tissue tumours by cell surface molecules

This study is aimed at the characterization of soft tissue tumours (STT) by means of cell surface molecules. To achieve this, normal mesenchymal tissues were extensively examined for expression of leucocyte differentiation (CD) antigens and HLA molecules. The panel of antigens finally examined in STT comprised CD10, CD13, CD24, CD34, CD36, CD56, CD57, HLA-A,B,C, beta 2-microglobulin, HLA-DR, -DP, and -DQ and the HLA-D-associated invariant chain (Ii). STT were determined by conventional histomorphological and immunohistochemical criteria. The immunohistological analysis was based on serial frozen sections, one of which was used to demonstrate CD53 antigen. This very broadly distributed leuco/histiocyte-restricted antigen allowed for the distinction between the background of interstitial "stromal" cells and the neoplastic population. In some STT, the expression pattern of the cell surface molecules corresponded to that in their non-neoplastic counterparts. The majority of STT, however, showed considerable changes in the cell surface immunophenotype compared to their cells of origin. These alterations consisted mainly in an aberrant induction/neoexpression and, to a much lesser extent, in an aberrant down-regulation/loss of cell surface antigens. Nevertheless, some immunophenotype configurations are described which, for the time being, can be considered to be useful supplements in the differential diagnosis of this complex class of tumours. The data also indicate considerable changes in cell surface antigen expression occurring in the course of neoplastic transformation of mesenchymal cells. Detailed analysis of alterations in the functional repertoire of neoplastic mesenchymal cells might provide new insights into the biology of STT, possibly leading to new concepts for therapeutic intervention.

Immunohistochemical study of childhood rhabdomyosarcomas and related neoplasms. Results of an Intergroup Rhabdomyosarcoma study project

The authors assessed a panel of immunohistochemical stains against 109 pediatric solid tumors, primarily rhabdomyosarcomas, under the auspices of the Intergroup Rhabdomyosarcoma Study. Fresh tumor tissue received from participating organizations was divided into portions that were either frozen or fixed in formalin, alcohol, or B5. Immunostaining was performed by the avidin-biotin complex method using monoclonal antibodies to desmin, neurofilaments, vimentin, cytokeratin, and leukocyte common antigen on cryostat sections. Tissue was also embedded in paraffin and stained with antimuscle-specific actin (MSA) and polyclonal antibodies to desmin, creatine kinase M subunit (CKM), myoglobin, and neuron-specific enolase (NSE). Antidesmin staining of cryostat sections was the most sensitive indicator of rhabdomyosarcoma (58 of 62 specimens positive). Results with this reagent in alcohol-fixed and formalin-fixed tissue were similar (46 of 56 positive versus 43 of 56 positive, respectively) and comparable with results with anti-MSA in formalin-fixed tissue (43 of 55 positive). However, the proportion of cells stained by antidesmin was higher in alcohol-fixed tissue than in formalin-fixed tissue. Staining with antimyoglobin and anti-CKM was much less satisfactory, with positivity rates of 17 of 37 and 11 of 57, respectively, in formalin-fixed rhabdomyosarcomas. Immunostaining of muscle markers revealed evidence of myogenesis in six undifferentiated sarcomas and in two sarcomas with inadequate histologic study on hematoxylin-eosin-stained sections. However, positivity was also noticed in samples of fibromatosis, Wilms' tumor, ectomesenchyoma, peripheral primitive neuroectodermal tumor, renal rhabdoid tumor, myositis ossificans, malignant fibrous histiocytoma, and embryonal sarcoma of the liver. The authors conclude that combined use of antidesmin and anti-MSA enhances the diagnosis of childhood sarcomas, especially when employed with other techniques such as electron microscopic study.

Atypical primitive neuroectodermal tumors. Comparative light and electron microscopic and immunohistochemical studies on peripheral neuroepitheliomas and Ewing's sarcomas

Recently, primitive neuroectodermal tumors (PNETs) have been shown to cover a wide spectrum of small round cell sarcomas, probably including some Ewing's sarcomas (ESs) and extraskeletal Ewing's sarcomas (EESs), in addition to classical peripheral neuroepitheliomas (PNs). In studies of small cell sarcomas, we found a group of undifferentiated tumors resembling PNETs with some features of neuroectodermal differentiation, but possessing areas of relatively large, pleomorphic cells. To clarify the nature of these tumors and their relationship to PNETs, we examined the variety of histological, immunohistochemical and ultrastructural features of 11 small cell sarcomas. Five of these tumors were composed of uniform, small round cells and were classified as PNs because of the presence of definite Homer-Wright rosettes and fibrillary processes. The presence of well developed neurite-like processes containing neurosecretory granules and immunoreactivities for various neural markers suggested that these PNs showed more advanced neuronal differentiation. Two tumors, with the classical features of ES, showed no ultrastructural evidence of neuronal differentiation, although only gamma-gamma neuron-specific enolase (NSE) positivity was detected. Four undifferentiated tumors with atypical features, included in this study as an atypical PNET group, showed certain neuroectodermal characteristics, such as ganglion cell differentiation, perivascular pseudorosettes, and gamma-gamma NSE reactivity. It is concluded from this study that PNETs may include small round cell tumors showing different degrees of neuro-ectodermal differentiation and some histological variations.

Prognostic value of histopathology in Ewing's sarcoma. Long-term follow-up of distal extremity primary tumors

The pathologic material from 56 patients diagnosed initially as Ewing's sarcoma of the distal extremity and treated on National Cancer Institute protocols between 1968 and 1984 was reviewed and correlated with clinical outcome. Histologically, the tumors were categorized, based on recent pathologic criteria, into three diagnostic groups: (1) typical Ewing's sarcoma, (2) atypical Ewing's sarcoma, and (3) other (predominantly peripheral neuroepithelioma [PN]). Thirty-two patients (57%) had typical Ewing's, 13 (23%) were atypical, and 11 (20%) were in the "other" diagnostic category (seven [13%] PN, two primitive rhabdomyosarcoma, one primitive sarcoma of bone, and one synovial cell sarcoma). No cases of metastatic neuroblastoma, osteosarcoma, or lymphoma were found. Forty-five patients had localized disease at diagnosis; 11 had metastases. Patients with typical Ewing's sarcoma were less likely to have metastatic disease at the time of diagnosis. Only two of 32 patients with typical Ewing's sarcoma had metastases compared with nine of 24 patients in the two other groups. The pattern of relapse was also different in these other groups compared with typical Ewing's patients; five patients developed lymph node metastases and two patients developed brain metastases. Although the presence of metastatic disease at diagnosis was a strong negative prognostic factor, our histologic grouping was independently prognostic of clinical outcome in patients with localized disease. Patients with typical osseous Ewing's sarcoma had an improved overall survival (P2 = 0.03) and patients with other tumors (neither typical nor atypical Ewing's sarcoma) had a poorer disease-free survival (P2 = 0.02). Since no generally accepted histopathologic prognostic criteria exist for Ewing's sarcoma, the potential value of our proposed classification should be evaluated in a larger retrospective and a prospective study.

Soft tissue Ewing's sarcoma. Characterization in established cultures and xenografts with evidence of a neuroectodermic phenotype

This study characterizes the histogenesis of soft tissue Ewing's sarcoma (StEs) based upon an analysis of three tumors. Long-term cultured cell lines and nude mice xenografts were established from original neoplasms or from their metastases. Histologically they revealed a small round cell pattern without signs of differentiation. Several ultrastructural features of neural type were found; the same were also seen on culture cell lines. Moreover, immunohistochemical study for neural markers revealed the presence of HNK-1, NSE, LIRC-LON 36, S-100 protein, glial fibrillary acidic protein, neurofilaments (70 kilodaltons), and chromogranin; some of these markers were present only in the transplants. Cytokeratin was also seen. The translocation t(11;22)(q24;q12) was found in all three neoplasms together with other chromosomal abnormalities. N-myc RNA gave negative results whereas c-myc RNA was expressed. Therefore it may be postulated that StEs displays neuroectodermal features somewhat similar to those seen in peripheral neuroepithelioma as well as in atypical Ewing's sarcoma of bone.

Neural differentiation in small round cell tumors of bone and soft tissue with the translocation t(11;22)(q24;q12): an immunohistochemical study of 11 cases

Clinical, cytogenetic, histopathologic, and immunohistochemical data were obtained in a series of 11 small round cell tumors (SRCT) of bone and soft tissue with the translocation t(11;22) (q24;q12). Ten cases were primary in bone, and one was of extraskeletal origin. According to conventional histopathologic criteria, 10 cases were Ewing's sarcomas (ES) and one was a peripheral neuroectodermal tumor (PNET). Besides the t(11;22), six cases had additional chromosomal aberrations, including trisomy 7 and partial trisomy for the long arm of chromosome 1, which have both been described as nonspecific secondary abnormalities often associated with tumor progression. The tumors were screened for neural differentiation with an antibody panel consisting of neuron-specific enolase, S100 protein, Leu-7, chromogranin, synaptophysin, and neurofilament. Three cases of ES were positive for S100 protein. The PNET and one case of ES were positive for neuron-specific enolase. All of the remaining immunohistochemical stains were negative. Hence, five of 11 SRCT of bone or soft tissue with the t(11;22) showed morphologic and/or immunohistochemical evidence of neural differentiation. In this limited series of cases, no cytogenetic or prognostic differences could be demonstrated between cases with and without a neural phenotype. Our results support the hypothesis that SRCT of bone of soft tissue with the t(11;22) form a single biologic entity displaying varying degrees of neuroectodermal differentiation. The clinical significance of additional cytogenetic abnormalities and of morphologic or immunohistochemical evidence of neural differentiation in this group of tumors needs to be further studied.

Neuroblastoma and other childhood neural tumors: a review

Neuroblastoma is the most common nonhematopoietic solid tumor of childhood and has been intensively studied for at least 4 decades. Despite this, few predictive histopathologic clues to its behavior exist. Age, anatomic sites of occurrence, and clinical stage have traditionally been the only reliable prognostic factors in this disease. A number of laboratory studies that focus on biologic features such as neurotransmitter synthesis (adrenergic and noradrenergic catecholamines), neurotransmitter enzyme expression (dopamine beta hydroxylase, choline acetyl transferase), cytogenetics (homogeneously staining regions, double minute chromosomes, chromosome 1p deletions), molecular genetics (N-myc oncogene amplification and expression), and immunophenotype (surface epitopes such as HLA antigens and GD2 ganglioside and intracytoplasmic determinants such as neurofilament protein, synaptophysin, chromogranin, and neuron specific enolase) now enable the pathologist to predict clinical course in many cases and to distinguish bona fide neuroblastomas, regardless of age, site, or histologic appearance, from a host of related but distinctly separate neuroectodermal tumor entities with apparent different histogenesis, treatment sensitivity, and prognosis.

Immunohistochemical expression of neuron-specific enolase and Leu 7 in Ewing's sarcoma of bone

Neural features have been documented in a series of small round cell tumors of bone, previously classified as Ewing's sarcoma of bone (ESB), using light microscopic, ultrastructural, immunohistochemical, and in vitro techniques. To date, correlation of the presence of these features in ESB with clinical outcome has not been performed. The authors investigated the clinical relevance of positivity to antibodies against neuron-specific enolase (NSE) and Leu 7 (HNK 1) using the avidin-biotin complex technique in 40 cases of ESB seen at St. Jude (Memphis, TN) during the period 1968 to 1986. Twenty-three cases (58%) were positive for NSE and/or Leu 7. The median disease-free survival of patients with localized tumors and NSE and/or Leu 7 positivity was 3.8 years compared to a median disease-free survival of 1.6 years for those without these markers and localized disease. Using the log-rank test, a statistically significant difference was shown in these two groups of patients (P = 0.049). The authors conclude that in this relatively small series ESB commonly expresses NSE and/or Leu 7 and that the presence of these markers is of no prognostic significance overall, but that in patients with localized ESB the presence of NSE and/or Leu 7 by immunostaining may be a favorable prognostic indicator.

Comparative study of neuroectodermal tumor and Ewing's sarcoma of the bone. Histopathologic, immunohistochemical and ultrastructural features

We carried out a histologic, immunohistochemical and ultrastructural study of 19 tumors, previously classified as Ewing's sarcoma of the bone (ESB). The tumors were categorized histologically into four groups according to the presence or absence and the distribution of Homer-Wright rosettes, together with the immunohistochemical and ultrastructural features: 1) neuroectodermal tumor of bone (NTB) with diffusely dispersed rosettes (4 cases), 2) conventional ESB totally lacking the rosettes (9 cases), 3) intermediate-type tumor with characteristics of both NTB and ESB (4 cases), and 4) spindle cell-type tumor with focal rosettes (2 cases). Ultrastructurally, NTB contained neurotubules and neurosecretory granules, whereas ESB consisted of only undifferentiated cells. Immunoreactivity with antineural antibodies, such as Leu-7, and those against synaptophysin, NSE, neurofilament, and chromogranin, was detected in the majority of NTB, in intermediate- and spindle cell-type tumors and in two of the nine cases of ESB. In view of these findings, we propose that use of the term "neuroectodermal tumor of the bone" should be restricted to tumors with an extensive distribution of rosettes, and that those without unequivocal rosettes should be classified as ESB, although ESB may be the most undifferentiated form of NTB and some overlap may occur between the two tumor types.

Clinical and radiologic analysis of 13 cases of primary neuroectodermal tumors of bone

Radiographs and clinical charts were reviewed in a series of 13 cases of primary neuroectodermal bone tumors, involving 9 males and 4 females, aged from 3 to 32 years (average: 15 years). The average delay between the onset and diagnosis was 5 months. Fever and other systemic symptoms were present in 6 cases; in 4 cases a fracture was the mode of presentation. Seven patients had metastases (4 involving bone) at the time of presentation. Only one patient is still alive after 5 years. In the 10 patients who died as a direct result of the tumor, death occured on average 8 months following diagnosis if metastases were present initially, and 36 months after the diagnosis otherwise. Tumors predominantly involved the leg (7 cases), the pelvis (2 cases), and the humerus (2 cases), the involvement being both diaphyseal and metaphyseal. The radiologic appearance is that of an aggressive, poorly demarcated tumor, with cortical destruction, periosteal reaction and soft tissue invasion. Comparison with Ewing sarcoma shows little radiologic or clinical difference, except for a poorer prognosis in neuroectodermal bone tumors. Both bone tumors may have a similar neuroectodermal origin, with Ewing sarcoma representing the undifferentiated variety.

Peripheral neuroectodermal sarcoma of soft tissue (peripheral neuroepithelioma): a pathologic study of ten cases with differential diagnosis regarding other small, round-cell sarcomas

Peripheral neuroepithelioma of soft tissue belongs to the group of peripheral neuroectodermal tumors (PNETs), but because of its clinical, biological, and morphological characteristics, it differs from other small, round-cell sarcomas that appear in children (neuroblastoma) or in the thoracopulmonary region (Askin's tumor) and bone (peripheral neuroectodermal sarcoma of bone). We report ten new cases of such PNET variety, based on their histologic, immunohistochemical, and electron microscopic findings. In all of these cases, the clinicopathologic correlations demonstrated high malignancy, with an ominous outcome in nine cases. The mean age of the patients was 32.6 years and there was a clear male predominance (eight men, two women). Histologically, the presence of Homer-Wright rosettes is mandatory for diagnosis, being complemented with positive immunohistochemistry for several neural immunomarkers using paraffin-embedded material. Neuron-specific enolase, E-36, HNK-1, and chromogranin neural markers proved to be positive in a high number of cases, but other markers (S-100 protein, synapto-physin, GFA protein, and neurofilaments [70 kilodalton]) were absent. Electron microscopy confirmed the presence of neural structures, both by scanning and transmission electron microscopy.

Ewing's sarcoma. A retrospective study of histological and immunohistochemical factors and their relation to prognosis

Histological and immunohistochemical features of 87 patients with conventionally diagnosed Ewing's sarcoma were studied retrospectively on routinely processed material and evaluated with regard to prognostic significance. 74% were convincingly positive when stained for vimentin, 13% were doubtful, and 13% were negative. A varying degree of positivity for neuron-specific enolase (NSE) was found in 15%; these cases all co-expressed vimentin. A single tumour contained scattered cytokeratin-positive cells. Positivity for the leukocyte common antigen (LCA) could be demonstrated in three cases; these were excluded from the statistical analysis of prognostic factors. Growth pattern, soft tissue invasion, monomorphic or dimorphic cell population, and PAS-, NSE- or vimentin-positivity did not influence survival significantly. However, prognosis was increasingly poor with increasing degree of necrosis: median survival was 28 months for grade I necrosis (less than 10%), 16 months for grade II (10-50%), and 11 months for grade III (greater than 50%), p less than 0.0005. A mitosis count of less than 1 per high-powerfield (HPF) was correlated to a median survival of 26 months, greater than or equal to 1 per HPF to 12 months, p less than 0.05. The findings indicate some degree of heterogeneity in Ewing's sarcoma which may be related to primitive peripheral neuroectodermal tumours (PNETs), or be a true blastoma. In future trials, diagnostic criteria (including immunohistochemistry) should be clearly defined and materials should be large enough to allow for stratification according to prognostic factors.

Peripheral neurogenic tumors of the soft tissues in children and adolescents: a clinicopathologic study of 139 cases

A review of over 900 soft tissue neoplasms in children and adolescents revealed 139 neurogenic tumors in 122 patients from newborn to 20 years of age, which had been accessioned in a 25-year period. Based upon clinicopathologic criteria, 84 (60%) tumors were regarded as unequivocally benign or borderline and the remaining 55 (40%) were malignant. The average age at diagnosis for the entire series was 10 years; the sex distribution was approximately equal; and the trunk (66, 48%) was the most frequent topographic site, followed by the head and neck (39, 29%) and extremities (31, 23%). Eighteen tumors (13%) were recognized at birth. Twenty-one patients (17%) had the stigmata of von Recklinghausen's neurofibromatosis (VRN). Neurofibromas and cellular peripheral nerve sheath tumors accounted for 43% (60 cases) of the diagnoses; these 60 neoplasms occurred in 41 patients, 12 of whom had VRN. The second largest category of neoplasms (38 cases, 28%) was the primitive neuroectodermal tumor (PNET) including the subset of "malignant small cell tumor of thoracopulmonary origin" or Askin tumor. The PNETs other than the Askin tumor (26 cases) presented mainly on the trunk (63%) and head and neck region (33%), showed a male predilection (58%) and had a mean age at diagnosis of 7 years. Askin tumors (12 cases) were, by definition, confined to the chest wall or thoracic cavity, showed a female predilection (71%), and presented in the second decade (82%, mean age 14 years). There were 16 (11%) malignant peripheral nerve sheath tumors, seven of which occurred in children with VRN. Six other categories of neurogenic tumors constituted the remaining cases. Our findings indicate that neurogenic neoplasms are an important nosologic group of soft tissue tumors in the pediatric population.

Pigmented esthesioneuroblastoma showing dual differentiation following transplantation in nude mice. An immunohistochemical, electron microscopical, and cytogenetic analysis

Esthesioneuroblastoma (ESTH) is a neuroepithelial-cell-derived neoplasm of the olfactory mucosa composed of homogeneous small round cells which contain neurosecretory granules. Melanin has been detected in such tumours only occasionally. Here we describe a new case of ESTH with divergent differentiation. The primary neoplasm was found in a 67 year-old female, involving the left nasal and maxillary sinus; she died of cerebral metastasis ten months after diagnosis. Histologically only small round cells were seen, with S-100 and NSE positivity. Electron microscopy revealed neurosecretory granules and filaments, as well as the occasional presence of melanosomes. A nude mice xenograft line has been established, and is presently in its ninth transfer. Two cell types are present: small round-to-spindle shaped cells with neural features, and large epithelial-like ones. Both immunohistochemistry and electron microscopy confirm this dual differentiation, with the presence of membrane-bound dense-core neural secretion, as well as melanosomes of neuroectodermal origin. Additionally, an in vitro cell line has been established. Cytogenetic analysis confirmed the presence of both malignant human melanoma patterns; non-random abnormalities in chromosomes 1 and 6, extra copies of chromosome 7. Duplication of the long arm of chromosome 14, as seen in olfactory neuroblastoma, is also seen.