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Peripheral primitive neuroectodermal tumor (peripheral neuroepithelioma) in children. A review of the St. Jude experience and controversies in diagnosis and management.

All patients diagnosed with primitive neuroectodermal tumor (PNET) and extraosseous Ewing's sarcoma in one institution between 1962 and 1987 were reviewed. Of the 26 cases studied, 16 had been diagnosed originally as PNETs, seven tumors were rediagnosed as PNET or EOE by histologic review, and three tumors had an original diagnosis of extraosseous Ewing's sarcoma. To determine whether these diagnoses determine a group of tumors with unique biologic behavior and identifiable pathologic characteristics, clinical and treatment response data were compiled, and electron microscopic and immunohistochemical studies were done for those patients with adequate samples. With combined modality therapy, this group achieved a substantially shorter disease control interval than patients with disseminated osseous Ewing's sarcoma or disseminated neuroblastoma--10.8 months versus 17 months and 16 months, respectively. The pattern of relapse and distant spread also differed among these tumor types. Immunohistochemical studies (for example, neuron-specific enolase and beta 2 microglobulin) were helpful in confirming the diagnosis but were not definitive in themselves. Tentative diagnostic criteria are proposed for use in studies designed to provide further information on the nature and treatment of PNET. Some of the controversies regarding diagnosis are discussed. The authors propose a uniform approach to treatment of extraosseous Ewing's sarcoma and PNET in order to try to clarify their relation.

Adolescent

MIC2 is a specific marker for Ewing's sarcoma and peripheral primitive neuroectodermal tumors. Evidence for a common histogenesis of Ewing's sarcoma and peripheral primitive neuroectodermal tumors from MIC2 expression and specific chromosome aberration.

This study reports on the specific expression of the MIC2 gene, a pseudoautosomal gene located on the short arms of the X and Y chromosomes, on Ewing's sarcoma (ES) and peripheral primitive neuroectodermal tumor (pPNET) cells. The gene product, a cell membrane protein, is recognized by the newly established monoclonal antibody (MoAb) HBA-71 and the previously described MoAb 12E7 and RFB-1. Furthermore, the reaction pattern of the MIC2 antibodies, especially HBA-71, with normal tissues and a great number of benign and malignant tumors (70 different tumors, 199 tumor samples), as well as the correlation between the specific chromosomal aberrations, i.e., the t(11;22) and the del(22) and the expression of this antigen, are demonstrated. Both ES and pPNET cells express the MIC2 gene in very high amounts, which represents a highly selective and almost unique feature of these cells, making an assignment of these tumors in one entity even more likely. The MIC2 antibodies are of great value for clinical and research purposes.

12E7 Antigen

Malignant peripheral primitive neuroectodermal tumor of the uterus.

Peripheral primitive neuroectodermal tumor (PPNET) is rare, occurring most often in young adults. Approximately 50 cases have been reported, with only four cases involving the female genital tract. We report the fifth patient. The term "PPNET" should be used only for tumors with neuroectodermal elements exclusively that occur at sites outside the central and sympathetic nervous system. The pathologic differential diagnoses include rhabdomyosarcoma, immature malignant teratoma, small cell carcinoma of the cervix, and ganglioneuroma. Therapy for this tumor has varied, and no effective regimen has been established.

Adolescent

Peripheral primitive neuroectodermal tumors. Diagnosis, classification, and prognosis.

In conclusion, the group of peripheral primitive neuroectodermal tumors has been redefined in recent years on the basis of cytogenetic, molecular genetic and more precisely defined histopathologic characteristics. Although in the past, many tumors has been called Ewing's sarcoma, currently this diagnosis is limited to tumors which cannot be more specifically classified on the basis of their ultrastructural and immunophenotypic characteristics. Most small round cell tumors previously classified as Ewing's sarcoma are now classified as peripheral PNET. The consistent cytogenetic abnormality in Ewing's sarcoma and peripheral PNET and patterns of neurotransmitter enzymes have supported a common neuroectodermal origin. The precise characterization of soft tissue Ewing's sarcoma is further complicated by the several primitive rhabdomyosarcomas that may exhibit a similar light microscopic appearance. The importance of histopathologic distinction among these various round cell tumors of childhood is well recognized. Furthermore, primitive tumors with overlapping neural and mesenchymal features, known as malignant ectomesenchymoma, are now identified more often than previously. Finally, molecular biologic and cytogenetic differences between peripheral PNET and neuroblastoma have confirmed their clinical and biologic differences, in spite of their morphologic similarities. Molecular genetic and flow cytometric evaluation have contributed to the distinction of groups with prognostic significance and offer possibilities for new clinical trials.

Adolescent

Peripheral primitive neuroectodermal tumors. A flow cytometric analysis with immunohistochemical and ultrastructural observations.

Flow cytometry of classical neuroblastoma has provided provocative evidence that cell cycle and ploidy analysis generate prognostically useful information. To determine whether such analyses of peripheral primitive neuroectodermal tumors might yield similar results, formalin-fixed, paraffin-embedded tissue specimens from 19 peripheral primitive neuroectodermal tumors, each previously characterized by immunohistochemical or ultrastructural study, were assessed. An acceptable histogram was obtained in 16 cases. Of these, nine neoplasms were diploid and seven contained aneuploid DNA. Among patients with diploid lesions, four were free of disease, whereas three had persistent or recurrent disease, and two had died of tumor. Among patients with aneuploid neoplasms, four were free of disease, one had recurrence, and two had died. There was no apparent correlation between immunophenotype and proliferative activity with the clinical outcome. Among aneuploid peripheral primitive neuroectodermal tumors, DNA index did not predict survival. Hence, cell cycle and DNA ploidy analyses do not appear to contribute to the prognostic assessment of peripheral primitive neuroectodermal tumors, as they do to presumably related neoplasms of the central and peripheral nervous system.

Aneuploidy

Cutaneous angiosarcoma as a second malignant neoplasm after peripheral primitive neuroectodermal tumor.

Second malignant neoplasms (SMN) in late childhood or young adulthood in individuals who have been successfully treated for an initial malignancy have emerged as a late effect of therapy in survivors of childhood cancer. Although radiation therapy is frequently implicated, chemotherapy with alkylating agents and antimetabolites has also been associated with SMN. Soft tissue sarcomas are among the most frequent primary malignancies complicated by a SMN and account for a majority of nonhematolymphoid SMN. We present the clinical and pathologic findings in a patient who had a peripheral neuroepithelioma (primitive neuroectodermal tumor, PNET) of the soft tissues diagnosed at 17 years of age, was treated with high-dose irradiation and multidrug chemotherapy, and developed an angiosarcoma 14 years later. This case represents an uncommon combination of mesenchymal malignancies in a young patient with an unusually favorable clinical course following the diagnosis of PNET.

Adolescent

Overexpression of the pseudoautosomal gene MIC2 in Ewing's sarcoma and peripheral primitive neuroectodermal tumor.

Ewing's Sarcoma (ES), the second most frequent bone tumor in childhood and adolescence, and the probably closely related peripheral primitive neuroectodermal tumor (pPNET) share a unique cytogenetic translocation between chromosomes 11 and 22. Both of them expose high amounts of a glycoprotein on their cell surface, which can be specifically detected by the mAb HBA-71. The cDNA coding for the HBA-71 antigen was isolated by screening a cDNA expression library constructed from a pPNET-derived cell line. Nucleotide sequencing revealed the HBA-71 antigen to be the product of the pseudoautosomal gene MIC2 previously identified by the mAb 12E7 in haematopoietic cells. This antigen is a glycoprotein with a molecular weight of about 29,000 and is expressed in low amounts in most human cell lines and probably normal tissues and tumors with only a few exceptions. In T-cells the antigen is involved in cell adhesion processes. In ES- and pPNET-derived cell lines MIC2 expression is significantly enhanced. No gross changes in posttranslational modification could be observed. The high expression results in easy and specific detection of the antigen in immunocytochemical analysis of paraffin embedded tissue sections making HBA-71 a useful tool in tumor diagnosis.

12E7 Antigen

Cytogenetic analysis of primitive neuroectodermal tumors. Absence of the t(11;22) in two of three cases and a review of the literature.

Cytogenetic analyses on direct and short-term cultures from three peripheral primitive neuroectodermal tumors (PNET) showed only one tumor with the t(11;22)(q24;q12), a translocation reported as characteristic of this tumor type. A second tumor contained rearrangements including apparent deletions of chromosomes 11 and 22 between bands 11q21 and 11qter and between bands 22q11.2 and 22qter, respectively. A third tumor contained two normal copies of 11q but appeared to be monosomic for 22. We consider these findings in light of a survey of the PNET literature.

Adolescent

Congenital primitive neuroectodermal tumor with epithelial and glial differentiation. An ultrastructural and immunohistochemical study.

A congenital primitive neuroectodermal tumor associated with epithelial and glial elements is described. This soft-tissue tumor present on the right temple of a newborn boy consisted mainly of small round cells of the primitive neuroepithelial type, occasionally forming rosettes. The other components were focal glandular structures producing mucin, and aggregates of epithelioid cells bearing clear cytoplasm, both being distributed throughout the entire tumor. Additional glandular and clear cell components were strongly positive for various epithelial markers, such as carcinoembryonic antigen, epithelial membrane antigen, and cytokeratin. Epithelioid cells were also positive for neuron-specific enolase and S100 protein. Glial differentiation was evidenced in some of the epithelioid cells by localization of cytoplasmic glial fibrillary acidic protein. These findings suggest that this tumor derives from a remnant of a neural crest, and the possibility of a special type of peripheral primitive neuroectodermal tumor is considered.

Epithelium

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.

Actins

MRI and pathological findings in two cases of Askin tumors.

Askin tumors are primitive peripheral neuroectodermal tumors (PPNET) located in the thoracopulmonary region. This entity was first proposed in 1979 by Askin et al. These highly malignant tumors occur primarily in children and young adults. Pre- und postoperative MRI findings are presented for two pathologically proven cases. MRI is the most appropriate imaging modality for the diagnosis and eventual follow-up for these tumors. They appear homogenous, and iso- or discretely hypointense in comparison to the spinal cord on T1-weighted images and hyperintense on proton density and T2-weighted images. They show a very stark contrast enhancement after i.v. injection of paramagnetic contrast agents. Sharp tissue borders, and exact tumor extension were shown in both cases. The high signal intensity on T2-weighted images was not altered by chemotherapy.

Adult

Monoclonal antibody MB2: a potential marker for Ewing's sarcoma and primitive neuroectodermal tumor.

The small round-cell tumors of childhood present difficulties in diagnosis when differentiation is not apparent. Immunohistochemistry is helpful; however, the only antigen consistently detected in Ewing's sarcoma is vimentin, which may also be detected in the other types of small-cell neoplasms. The monoclonal antibody (MAb) MB2 is marketed as a B-lymphocyte marker that can be used on paraffin-embedded tissue. To determine its specificity, we performed immunohistochemical staining on pediatric tumors with MB2. These included 55 cases of small round-cell tumors (lymphomas, Ewing's sarcoma, peripheral primitive neuroectodermal tumors [PNET], neuroblastomas, rhabdomyosarcomas, and nephroblastomas). MB2 positivity was detected in all B-cell lymphomas and in seven of nine cases of Ewing's sarcoma and three PNET. In neuroblastomas only differentiating ganglion cells were positive. In rhabdomyosarcomas only large rhabdomyoblasts were positive. Blastema of nephroblastomas was negative. Thus, in cases of poorly differentiated small round-cell tumors, MB2 was positive in all B-cell lymphomas, most Ewing's sarcomas and all cases of PNET. Lymphomas were distinguished by staining for leukocyte-common antigen and PNET by neuron-specific enolase. Therefore, the addition of MB2 to a discrete panel of antibodies may prove useful in the diagnosis of Ewing's sarcoma and PNET.

Adolescent

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.

Adolescent

[Autologous peripheral stem cell transplantation in children].

19 children between 3 and 23 years underwent 79 leukapheres for collection of blood stem cells. In children suffering from acute lymphoblastic leukemia (ALL), Non Hodgkin's Lymphoma (NHL) and Ewing's Sarcoma (ES) we collected 6.87 x 10(4) CFU-GM/kg (range 2,65-21.7), if collections were started with the first platelet rise. In children with peripheral primitive neuroectodermal tumors (PNET) and neuroblastoma (NBL) we gained only 1.20 x 10(4) CFU-GM/kg (range 0.09-2.24). 17 children received high dose chemoradiotherapy and peripheral stem cell +/- bone marrow rescue. 9 suffered from solid tumors, 8 from hematopoietic malignancies. 9 were transfused with peripheral stem cells only, 8 received bone marrow in addition. Time to reach 0.5 x 10(9)/l granulocytes was very short-median 31 days (12-65), in 4 children receiving more than 5 x 10(4) CFU-GM/kg 12 to 13 days, only. On January 31st, 1989 6/17 children are alive in complete remission after a median observation time of 14.5 months (3-26) after autologous stem cell transfusion, one child is alive in "no remission", 7 died with relapse, 3 died because of infections (2 x aspergillosis, 1 x pseudomonas septicemia). The collection of blood derived stem cells by leukaphereses was well tolerated even in very small children and easily repeatable. With optimal timing high stem cell numbers were obtainable, resulting in a very short duration of posttransplant granulocytopenia.

Adolescent

Soft tissue tumors in first year of life: a report of 190 cases.

A comprehensive review of soft tissue tumors in children and adolescents disclosed the presence of 190 neoplasms in 183 patients, which were diagnosed in infants between birth and 12 months of age; these infants represented approximately 20% of our entire pediatric soft tissue tumor series. In excess of 75% of cases were pathologically benign with the hemangioendothelioma, lymphangioma, and fibromatosis-myofibromatosis constituting the majority of cases in this category. Fibrous histiocytoma and lipoblastoma were the other two benign entities. Congenital-infantile fibrosarcoma was considered a borderline tumor because of its infrequently manifested potential for metastasis; none of the 13 cases in the present study behaved in a malignant fashion. Embryonal rhabdomyosarcoma and peripheral primitive neuroectodermal tumor were the two principal types (17 of 27 cases) of malignant soft tissue tumors. In contrast to soft tissue tumors in the first two decades, those in the first year of life were more often benign despite their cellularity and presence of mitotic activity. Fibroblastic-myofibroblastic tumors were more frequent in this young age group, whereas neurogenic and myogenic tumors were relatively more common in children older than 1 year of age. The trunk and head and neck region were the preferred topographic sites rather than the extremities, which was the case in children beyond the first year of life.

Female

Laboratory investigation, genetics, and experimental models in sarcomas.

The sarcomas, particularly those of soft-tissue origin, pose substantial diagnostic challenges for the clinician and pathologist. Several small round cell sarcomas, including Ewing's sarcoma, peripheral primitive neuroectodermal tumor, and alveolar rhabdomyosarcoma, can be difficult to distinguish from one another. These same sarcomas can be difficult to distinguish from other small round cell tumors, including non-Hodgkin's lymphoma and neuroblastoma. Spindle cell sarcomas, including malignant peripheral nerve sheath tumor, synovial sarcoma, and leiomyosarcoma, present similar diagnostic challenges. This review discusses 1) recent advances in immunohistochemistry, electron microscopy, and cytogenetics that enable a specific diagnosis in virtually all sarcoma cases; 2) cell biology and oncogenetic implications of novel morphologic and genetic findings in sarcomas; and 3) clinical implications of the recent characterization of several family cancer syndrome genes.

Animals