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.     

Bone Marrow Metastasis in Ewing's Sarcoma and Peripheral Primitive Neuroectodermal Tumor: An Immunohistochemical Study

Bone marrow metastases from small round cell tumors can present diagnostic difficulties. In this study, we assessed the value of immunohistochemistry, using two monoclonal antibodies to CD99, for the diagnosis of metastatic disease in bone marrow trephine specimens from patients with Ewing's sarcoma or primitive neuroectodermal tumor (PNET). The proportions of specimens showing metastases were 10.3% with routine staining and 20.7% with immunohistochemistry. The specimens that were negative on conventional light microscopy and positive with immunohistochemistry all showed other abnormalities. The results do not support the routine use of immunohistochemistry in specimens that are normal by conventional light microscopy, but indicate that useful information may be gained in cases where marrow histology is obscured by fibrosis, necrosis, or distortion artefact. Neither of the two antibodies tested was superior for this purpose. Received January 17, 1997; accepted May 22, 1997     

DETECTION OF TERMINAL DEOXYNUCLEOTIDYL TRANSFERASE (TdT) IN NONHEMATOPOIETIC SMALL ROUND CELL TUMORS OF CHILDREN

In the differential diagnosis of small round cell tumors (SRCTs), terminal deoxynucleotidyl transferase (TdT) is often used as a marker for lymphoblastic lymphomas and leukemias. However, the specificity of TdT using the avidin-biotin-immunoperoxidase (ABC) method is not well documented. To address this issue, we stained paraffin-embedded biopsy specimens of 64 cases of childhood SRCTs using the ABC method with anti-TdT. For any TdT-positive tumors, an additional antibody panel for lymphoid markers was applied. Two patterns of TdT positivity were observed: (1) tumor specific, consisting of strong to moderate nuclear staining, and (2) scattered positive lymphoid cells, usually in a perivascular location and expressing T-cell markers. Analysis showed that 7 of 10 medulloblastomas stained with TdT in a tumor-specific pattern (4 cases moderately to strongly positive in 75-100 of tumor cells, 3 cases weakly to moderately positive in 25-50 of cells). Also, 1 of 19 rhabdomyosarcomas and 1 of 8 Ewing's sarcomas showed moderate to strong tumor-specific TdT staining in 100 and 10 of cells, respectively. Scattered TdT-positive lymphoid cells were observed in 27 of these 64 SRCTs. These findings emphasize that TdT positivity should not be relied upon exclusively for making a diagnosis of lymphoblastic leukemia or lymphoma or ruling out other SRCTs.     

Extracellular Matrix of Small Round cell Tumors of Childhood: An Immunohistochemical Study of 67 Cases

Sixty-seven childhood tumors were studied immunohistochemically for the extracellular matrix elements type IV collagen, laminin, and fibronectin. Tumors included Ewing's sarcoma, primitive neuroectodermal tumor, small cell osteosarcoma, neuroblastoma or ganglioneuroblastoma, rhabdomyosarcoma, and lymphoma. It was found that small cell osteosarcoma was often positive for fibronectin but not type IV collagen or laminin, a new observation. In the lymphomas, matrix proteins were rarely found. Ewing's sarcoma was variably positive for type IV collagen and laminin, but fibronectin was absent. Extracellular laminin and fibronectin were found in one of two cases of primitive neuroectodermal tumor. In neuroblastoma and ganglioneuroblastoma, the matrix components were rarely found. These results, discrepant with findings in cultured cells, may reflect the altered capacity of tumors to produce these proteins in vitro, which suggests that caution should be exercised in drawing conclusions regarding the nature or histogenesis of tumors from data obtained with cultured tumor cells. Embryonal rhabdomyosarcoma frequently contained all matrix elements in the extracellular space and in a dotlike pattern in the cytoplasm; alveolar rhabdomyosarcoma rarely contained these proteins and never exhibited the dotlike pattern. The frequent finding of matrix proteins in embryonal rhabdomyosarcoma but only rarely in alveolar rhabdomyosarcoma and the unique immunostaining pattern in embryonal rhabdomyosarcoma may prove to be a useful adjunct in the diagnosis of childhood tumors.     

Cooperative Ewing's Sarcoma Studies 81/86: pathologico-anatomic and immunohistochemical findings and differential diagnosis of Ewing sarcoma

158 cases of the Cooperative Ewing's Sarcoma Trials (CESS 81/86), which have been documented at the Pediatric Tumor Registry, Kiel, were studied by conventional light microscopy and immunohistochemistry. There were 77 cases of typical Ewing's sarcoma with 70 cases being located in the skeleton and 7 in soft tissues. Of the 14 cases of atypical Ewing's sarcoma 7 cases each were localized in bone and in soft tissue, respectively. In contrast to typical Ewing's sarcoma, cells of atypical Ewing's sarcoma were larger and displayed more heterochromatin. Both, typical and atypical Ewing's sarcoma reacted positively for vimentin. Other stains were negative, notably the neuron specific enolase (NSE). In 55 cases a diagnosis of malignant peripheral neuroectodermal tumor (MPNT) was made. Histologically most of these tumors resembled atypical Ewing's sarcoma. By immunohistochemistry positive reactions were found for NSE, vimentin, protein S-100, neurofilaments and glial fibrillary acidic protein. In 3 cases a diagnosis of small cell osteosarcoma was made. There were 2 cases of undifferentiated sarcoma of bone, 2 cases of soft tissue sarcoma of undetermined histogenesis and 2 cases of rhabdomyosarcoma. Of the 4 tumors which could be investigated for response to polychemotherapy, 1 each corresponded to grade II and III, respectively, and 2 to grade IV according to the classification of histologic grade of regression established by Salzer-Kuntschik et al. (1983).     

The applicability of immunohistochemistry in the diagnosis and differential diagnosis of malignant soft tissue tumors. A reevaluation based on the material of the Kiel Pediatric Tumor Registry

The diagnosis and differential diagnosis of malignant soft tissue tumors not infrequently poses great difficulties, especially in those cases which lack any feature of differentiation by conventional light microscopy. These difficulties have been partially resolved through the application of ultrastructural investigations. Recently considerable progress has been achieved using immunohistochemistry. At the Kiel Pediatric Tumor Registry we were able to reduce the percentage of unclassified soft tissue sarcomas from 17.6% in 1982 to 4.5% in 1989. Particularly useful were antibodies against the different types of intermediate filaments, muscle-specific actin, myoglobin, and the neural markers neuron-specific enolase and protein S-100. In contrast to the expected immunophenotype rhabdomyosarcomas, malignant peripheral neuroectodermal tumors and malignant schwannomas showed expression of cytokeratins. Moreover, in many cases rhabdomyosarcomas and synovial sarcomas expressed neural markers. Ewing's sarcoma and malignant peripheral neuroectodermal tumor are histogenetically related, but differ in grade of neural differentiation. In all soft tissue sarcomas immunohistochemistry is very useful to obtain information on the cellular heterogeneity. Despite the great achievements not every soft tissue sarcoma can be diagnosed with certainty. There will always be a baseline of unclassified cases due to problems which are not caused by the tumor itself but rather by diagnostic circumstances.     

Diagnosis of neuroblastoma metastasis in bone marrow with a panel of monoclonal antibodies

Neuroblastoma, along with rhabdomyosarcoma, Ewing's sarcoma, and acute lymphoblastic leukemia/lymphoma, is one of the small, round-cell tumors of childhood. All of these malignancies show a propensity to metastasize to bone marrow. Occasionally when the clinical picture is unclear and the tumor is particularly anaplastic, it can be difficult to arrive at a diagnosis by conventional histological and biochemical procedures. In the present study, a panel of nine monoclonal antibodies was used to undertake a detailed analysis of seven bone marrows contaminated with tumor cells: six cases of stage IV neuroblastoma, and one case of stage IV-S neuroblastoma. The antibody profiles obtained were compared with those deduced from the studies of over 20 marrows from patients with acute lymphoblastic leukemia. A comparison of these data with those obtained from the studies of rhabdomyosarcoma and Ewing's sarcoma cell lines and tissues suggests that when high levels of tumor cells are present in the marrow, it is possible to obtain a confident diagnosis of either neuroblastoma or acute lymphoblastic leukemia. In addition, the immunocytological identification of neuroblasts in bone marrow enables accurate staging without histological examination.     

Spectrum of Pediatric Cancers in Mozambique: An Analysis of Hospital and Population-Based Data

The existing data provide little detail about the epidemiology of pediatric cancers in Mozambique. We aimed at characterizing the spectrum of pediatric cancers (0–14 years) diagnosed in Mozambique in two different calendar periods. Data were obtained from the Pathology Department of the Maputo Central Hospital (DP-HCM) (1999–2000 and 2009–2010), which receives virtually all samples for histopathological diagnosis in Maputo, with the exception of leukemia, and from the population-based Cancer Registry of Beira (2009–2010). In 1999–2000, the DP-HCM diagnosed 61 cancers. Burkitt lymphoma, malignant bone tumors, and rhabdomyosarcomas accounted for 24.6%, 11.5%, and 9.8% of all cases, respectively. In 2009–2010, the number of cancers increased to 150, reflecting a two- to threefold increase in the proportion of Kaposi sarcomas, non-Hodgkin lymphomas, nephroblastomas, and neuroblastomas. In 2009–2010, the Cancer Registry of Beira registered 34 cases, corresponding to an incidence rate of 9.7/100,000 inhabitants in this age group; Kaposi sarcomas, lymphomas, retinoblastomas, and nephroblastomas accounted for 29.4%, 23.5%, 8.8%, and 8.8% of all cases, respectively. These data show that pediatric cancers account for an appreciable burden in Mozambique, probably reflecting a high frequency of HIV-associated cancers and improved access to diagnosis, and highlight the potential for improving surveillance in this low resource setting.     

Significance of immunohistologic methods in the differential diagnosis of solid tumors in childhood

We have investigated 56 histologic and 13 cytologic specimens of malignant round cell tumors of childhood. The immunohistological detection of intermediate filament polypeptides, neuron specific enolase (NSE) as well as leukocyte common antigen (LCA) allows the histological classification of such tumors. Neuroblastomas demonstrate a positive reaction with antibodies to neurofilaments and NSE independent of differentiation. Rhabdomyosarcomas could be labeled by the desmin antibody, while Ewing sarcomas, malignant lymphomas as well as nonmuscular sarcomas only express vimentin. In nephroblastomas the intermediate filament specific antibodies reveal expression of keratin and vimentin in blastema cells, while tubules are only labeled by the keratin antibody. In undifferentiated nephroblastomas, which lack formation of tubules blastema cells are keratin negative and vimentin positive. Thus antibodies to intermediate filaments, LCA and NSE seem to be useful tools to distinguish the so called "round cell tumors" of childhood.     

Ewing's sarcoma/primitive neuroectodermal tumor of the chest wall

Ewing's sarcoma/primitive neuroectodermal tumor is the most common tumor of the chest wall in children and adolescents. It is extremely malignant with a high frequency of both metastatic spread and of local recurrence. Cure requires intensive therapy to control both distant and local disease. Surgery and high-dose radiotherapy can achieve equivalent local control; however, radiation is associated with the additional morbidities of second malignancy and a significant adverse impact on both cardiac and pulmonary function. The optimal therapeutic sequence is initial biopsy followed by induction chemotherapy with subsequent resection of the primary tumor. This approach will achieve the lowest incidence of tumor present at the margins of resection and, hence, need for postoperative radiotherapy. The chest wall is a rare site for tumors in children and adolescents. In a series reported from St Jude's Children's Research Hospital, chest wall tumors constituted only 1.8% of the solid childhood tumors. They are primarily mesenchymal in origin and the Ewing's sarcoma/primitive neuroectodermal tumors (PNET) predominate. This report concentrates on the later tumors. They are recognized to be extremely malignant, and cure in those who present with metastatic disease is very difficult to achieve. Recent advances in our understanding of their cytogenetic basis and optimal treatment are presented.     

EBV genome and immunoglobulin gene rearrangement in the differential diagnosis of nasopharyngeal carcinoma and lymphoma.

Head and neck tumors include nasopharyngeal carcinoma (NPC) and lymphoma. The differential diagnosis of these tumors is based on histology, immunocytochemical staining, and EBV serology. In rare cases it might be difficult to distinguish between NPC and lymphoma in HE section or biopsies. DNA hybridization with cloned EBV and human immunoglobulin gene fragments allows the detection of EBV-related sequences and immunoglobulin gene rearrangements. The presence of EBV genome supports the diagnosis of NPC or EBV related BL, while rearrangement of immunoglobulin genes points to B-cell lymphoma. The diagnosis in 11 patients suspected of head and neck tumors was carried out by hybridization of DNA extracted from the tumors and assayed with cloned EBV and IgHCJ DNA probes. One patient proved to have EBV-associated BL based on positive hybridization with EBV probes and immunoglobulin rearrangement, presenting a unique hybridization with cloned EBV DNA BamHI W fragment, with bands of 3.2 and 3.9 kb. BL was confirmed in this patient by demonstration of c-myc rearrangement. A second patient was negative in hybridization with EBV, and positive for immunoglobulin rearrangement, and therefore was diagnosed as having B-cell lymphoma. In seven patients NPC was confirmed by hybridization with EBV-DNA probes. In two patients, both NPC and B-cell lymphomas were excluded.     

EBV genome and immunoglobulin gene rearrangement in the differential diagnosis of nasopharyngeal carcinoma and lymphoma

Head and neck tumors include nasopharyngeal carcinoma (NPC) and lymphoma. The differential diagnosis of these tumors is based on histology, immunocytochemical staining, and EBV serology. In rare cases it might be difficult to distinguish between NPC and lymphoma in HE section or biopsies. DNA hybridization with cloned EBV and human Immunoglobulin gene fragments allows the detection of EBV-related sequences and immunoglobulin gene rearrangements. The presence of EBV genome supports the diagnosis of NPC or EBV related BL, while rearrangement of immunoglobulin genes points to B-cell lymphoma. The diagnosis in 11 patients suspected of head and neck tumors was carried out by hybridization of DNA extracted from the tumors and assayed with cloned EBV and IgHCJ DNA probes. One patient proved to have EBV-associated BL based on positive hybridization with EBV probes and immunoglobulin rearrangement, presenting a unique hybridization with cloned EBV DNA BamHI W fragment, with bands of 3.2 and 3.9 kb. BL was confirmed in this patient by demonstration of c-myc rearrangement. A second patient was negative in hybridization with EBV, and positive for immunoglobulin rearrangement, and therefore was diagnosed as having B-cell lymphoma. In seven patients NPC was confirmed by hybridization with EBV-DNA probes. In two patients, both NPC and B-cell lymphomas were excluded.     

"POLYPHENOTYPIC" TUMORS IN THE CENTRAL NERVOUS SYSTEM: Problems in Nosology and Classification

In recent years, there is increasing recognition of polyphenotypic high-grade malignancies in the non-central nervous system (CNS) tumor literature. Some of these tumors have been regarded as variants of primitive neuroectodermal tumor (PNET) or as extrarenal malignant rhabdoid tumors (MRTs). This report concerns two posterior fossa neoplasms, both of which displayed a "polyphenotypic" expression of neural, epithelial, myogenic, and glial markers, including synaptophysin, neurofilament, vimentin, glial fibrillary acidic protein, S-100, neuron-specific enolase, desmin, S antigen, MIC2, cytokeratin, epithelial membrane antigen, and carcinoembryonic antigen. One tumor showed complex intercellular junctions, cytoplasmic intermediate filaments, well-developed rough and smooth endoplasmic reticulum and Golgi apparatus, cilia, and neurosecretory granules. The other neoplasm showed pools of glycogen, desmosomes, and tonofilaments. The histological and ultrastructural appearances were inconsistent with glioma, PNET, meningioma, ependymoma, choroid plexus carcinoma, sarcoma, germ cell tumor, and other tumors in the World Health Organization classification. Although the polyphenotype raises the issue that these may represent variants of MRT or the atypical teratoid-rhabdoid tumor, the morphologic findings in the two cases were very dissimilar. Our two cases underscore the problems in nosology and classification of polyphenotypic tumors of the CNS. This is particularly significant, as therapeutic protocols for PNET, MRT, and non-CNS polyphenotypic tumors are different. We review the literature on polyphenotypic tumors and reiterate the difficulties in precise classification of these complex tumors.     

Kongenitaler melanotischer neuroektodermaler Tumor

Congenital melanotic tumors (MNT) are very rare tumors of childhood. Microscopic findings overlap with those of other small round cell tumors. The neoplasia is almost always benign and generally arises in the maxilla in the 1st month of life. The histogenesis is still controversial today. The idea of a neuroectodermal origin is the most frequently advocated hypothesis. The diagnosis is possible by the coexpression of epithelioid antigen containing cells and melanotic-like cells. The differential diagnosis includes other small round blue cell tumors such as Ewing’s sarcoma, neuroblastoma, PNET, or malignant lymphoma. Treatment of MNT has typically been surgical. We report a case of a 3-month-old infant with an unusual recurrent tumor. Molecular cytogenetic studies in our case did not show numeric or structural genetic changes. The expression of the growth factor VEGF in the neuroblastic tumor cells was high and the growth factor angiopoietin-1 was strongly expressed in the melanotic tumor cells.     

Pure Erythroid Leukemia Mimicking Ewing Sarcoma/Primitive Neuroectodermal Tumor in an Infant

Pure erythroid leukemia (PEL) is a rare type of acute myeloid leukemia (AML) with a very aggressive clinical course. Presentation as a myeloid/erythroid sarcoma is exceedingly rare. We describe an infantile PEL presenting as a multifocal myeloid sarcoma, clinically and pathologically mimicking Ewing sarcoma/PNET family of tumors. The patient died 8 weeks after the initial presentation due to widespread disease. Our case shows that PEL needs to be considered in the differential diagnosis of small round blue cell tumors in infancy. A meticulous workup including immunohistochemistry, flow cytometry, molecular, and cytogenetic studies was required to reach the diagnosis.     

Intracranial Ewing sarcoma

The occurrence of primary extraosseous Ewing sarcoma (EES) of the central nervous system (CNS) has only rarely been reported in the literature. It is important to distinguish this entity from the more common central primitive neuroectodermal tumor (PNET) of brain, since the management of these tumors is different from that of EES. We present the clinical, radiologic, and pathologic features of two cases of EES occurring in the brain. The diagnosis was further confirmed by detection of a rearrangement of the FLI1 and/or EWS gene loci in tumors from both patients using fluorescent in situ hybridization (FISH). Although rare, the possibility of EES should be considered particularly when tumors that arise near the meningeal surface of the brain and have the pathologic appearance of a PNET. Demonstration of t(11;22)(q24;q12) by molecular analysis essentially confirms the diagnosis and enables the oncologist to choose appropriate therapy.