A comparative study of immunohistochemical staining for neuron-specific enolase, protein gene product 9.5 and S-100 protein in neuroblastoma, Ewing's sarcoma and other round cell tumours in children

Superficial Neurocristic EWSR1::FLI1 Fusion Tumor: A Distinctive, Clinically Indolent, S100 Protein/SOX10-Positive Neoplasm

It is now understood that identical gene fusions may be shared by different entities. We report a distinctive neoplasm of the skin and subcutis, harboring the Ewing sarcoma-associated EWSR1::FLI1 fusion, but differing otherwise from Ewing sarcoma. Slides and blocks for 5 cutaneous neoplasms coded as other than Ewing sarcoma and harboring EWSR1::FLI1 were retrieved. Immunohistochemical and molecular genetic results were abstracted from reports. Methylation profiling was performed. Clinical information was obtained. The tumors occurred in 4 males and 1 female (median 25 years of age; range 19-69 years) and involved the skin/subcutis of the back (2), thigh, buttock, and chest wall (median 2.4 cm; range 1-11cm). Two tumors were present "years" before coming to clinical attention. The lesions were multinodular, circumscribed. and consisted of nests of bland, round cells admixed with hyalinized collagenous bands containing spindled cells. Hemorrhage and cystic change were often present; necrosis was absent. All were diffusely S100 protein/SOX10-positive; 4 of 5 were CD99-negative. One tested case was strongly positive for NKX2.2. A variety of other tested markers were either focally positive (GFAP, p63) or negative. Molecular genetic results were: EWSR1 exon 7::FLI1 exon 8, EWSR1 exon 11::FLI1 exon 5, EWSR1 exon 11::FLI1 exon 6, EWSR1 exon 7:: FLI1 exon 6, and EWSR1 exon 10::FLI1 exon 6. Methylation profiling (3 cases) showed these to form a unique cluster, distinct from Ewing sarcoma. All patients underwent excision with negative margins; one received 1 cycle of chemotherapy. Clinical follow-up showed all patients to be alive without disease (median 17 months; range 11-62 months). Despite similar gene fusions, the morphologic, immunohistochemical, epigenetic, and clinical features of these unique EWSR1::FLI1-fused neoplasms of the skin and subcutis differ substantially from Ewing sarcoma. Interestingly, EWSR1 rearrangements involved exons 10 or 11, only rarely seen in Ewing sarcoma, in a majority of cases. Superficial neurocristic EWSR1::FLI1 fusion tumors should be rigorously distinguished from true cutaneous Ewing sarcomas.

Primary renal primitive neuroectodermal tumor

Primitive Neuroectodermal Tumor of the kidney is a rare entity. Very few cases of primary renal PNET have been reported to date. Most literature about rPNET is isolated case reports. We report a case of rPNET in a 39-year-old male with a pre-operative diagnosis of renal cell carcinoma with renal vein thrombosis. The patient underwent radical nephrectomy with thrombolectomy, and histopathological examination revealed a highly aggressive tumor composed of monotonous sheets of round cells. Tumor cells were positive for CD 99 and FLI-1, hence confirming the diagnosis of Primitive Neuroectodermal Tumor. Post-surgery, patient was given VAC/IE-based adjuvant chemotherapy. In view of highly aggressive nature of this tumor, prompt diagnosis and imparting effective chemotherapy regimen to the patient is required, and it is important to differentiate PNET from other small round-cell tumors because of different therapeutic approach.

Primary Ewing Family of Tumors of the Jaw Has a Better Prognosis Compared to Tumors of Extragnathic Sites

PURPOSE

Primary Ewing sarcoma of the jaw is rare. The aim of this study was to describe new cases of primary Ewing sarcoma of the jaw and investigate reported prognostic factors of Ewing sarcoma in this series and treatment outcome.

MATERIALS AND METHODS

Six patients with primary Ewing sarcoma of the jaw were treated at the Memorial Sloan Kettering Cancer Center (MSKCC) from 1992 through 2013. Clinical data, pathology reports, treatment prescribed, treatment regimens, outcome, and follow-up information were reviewed.

RESULTS

Five of 6 patients were female and 5 cases were in the mandible. No patient presented with metastatic disease at diagnosis. All cases were positive for CD99, and 3 patients with genetic confirmation were positive for EWS-FLI1 fusion or EWSR1 gene rearrangement. All patients received induction multiagent chemotherapy and surgical resection and 2 patients received adjuvant radiotherapy. Total (grade IV) or nearly total (grade III) tumor necrosis in 3 of 5 patients (60%) assessed for histologic response to chemotherapy indicated intense sensitivity. All patients were alive and free of disease, with no history of local recurrence, at a median follow-up period of 6.5 years.

CONCLUSION

Patients with primary Ewing sarcoma of the jaw have a good prognosis and metastasis is an uncommon occurrence at initial presentation.

Open removal of a retained retrohepatic inferior vena cava filter with a residual primary neuroectodermal renal tumoral thrombus

Primary neuroectodermal renal tumours (PNET) are rare and aggressive neoplasms; thrombosis of the inferior vena cava (IVC) is associated with this entity. We report here the case of a 19-year-old man who experienced a new onset of abdominal pain. A CT scan revealed a large left renal mass, perirenal haematoma and IVC thrombosis. Owing to an acute drop in haemoglobin and subsegmentary pulmonary embolism, he underwent emergency selective renal artery angiography and embolisation of bleeding vessels and IVC filter (IVCF) placement. Once stable, he underwent a left radical nephrectomy and IVC thrombectomy; the pathology report confirmed PNET. 6 months later, imaging revealed a residual tumoral thrombus in the IVCF located in the retrohepatic IVC. The patient underwent removal of this device and the thrombus via a right thoracoabdominal approach. He recovered well and at 4 months, he continues his chemotherapy cycles.

Immunohistochemistry as potential diagnostic pitfall in the most common solid tumors of children and adolescents

Making a correct diagnosis when dealing with a small round blue cell tumor (SRBCT) of children and adolescents may be relatively straightforward if the tumor arises in the typical clinical setting and the classic pathologic features are all recognizable. However it is widely known that diagnostic difficulties may arise because of: (i) many tumors share overlapping morphological and/or immunohistochemical features; (ii) considerable clinical, pathologic, and immunohistochemical variations do exist; (iii) the increasing use of small biopsies in daily practice makes the diagnosis of these neoplasms more challenging. Accordingly, immunohistochemical analyses are currently mandatory in establishing the correct diagnosis. In this regard there is the need to identify more sensitive and specific immunomarkers useful in the distinction of the several tumor entities. Over the last decades, several markers, such as CD99, WT1 protein, desmin, myogenin, NB84, and INI1 have been identified, providing a considerable help in recognition of the most common solid tumors (ESW/pPNET, rhabdomyosarcoma, neuroblastoma, Wilms' tumor, desmoplastic small round cell tumor; malignant rhabdoid tumor) in children and adolescents. However, at the same time, their unusual, unexpected expression can result in a misinterpretation of the immunohistochemical results, especially by pathologists who are not familiar with oncologic pediatric pathology. Therefore the present review focuses on the potential immunohistochemical pitfalls which should be kept in mind by pathologists to prevent diagnostic errors when dealing with SRBCTs.

Primitive neuroectodermal tumor of the kidney in a young male: Case report and review of literature

Primitive neuroectodermal tumor of the kidney is a rare tumor. A total of approximately 79 primary renal cases have been reported to date. Primitive neuroectodermal tumors occur preferentially in the soft-tissues of the paravertebral region and chest wall, less frequently in extremities, with a slight male predominance. We report a case of primitive neuroectodermal tumor of the kidney in a 17-year-old male with a pre-operative diagnosis of renal cell carcinoma-stage 4. The patient underwent radical nephrectomy and histopathological examination revealed a highly aggressive tumor of monotonous sheets of round cells with focal areas of rosette formations and high mitotic rate with Ki67 index of 25-30%. Tumor cells were positive for CD 99 confirming the diagnosis of primitive neuroectodermal tumor. Primitive neuroectodermal tumor of the kidney needs to be kept in mind as a differential diagnosis in young adults presenting with a large kidney mass.

Primary sinonasal mucosal melanoma with aberrant diffuse and strong desmin reactivity: a potential diagnostic pitfall!

The broad morphologic spectrum, inherent immunophenotypic heterogeneity of malignant melanoma and its rarity in the sinonasal tract are major challenges in eliciting the correct diagnosis, which may lead to misclassification and inadequate medical management. Herein, we describe a single case of a 70 year-old male with sinonasal mucosal melanoma, exhibiting varying histologic phenotypes including small round blue cell morphology, epithelioid and focal rhabdoid morphology and strong, diffuse desmin immunoreactivity. These constellation of features initially prompted the diagnosis of rhabdomyosarcoma. The differential diagnosis in this anatomic area includes other malignant small round blue cell tumors of the sinonasal mucosa such as rhabdomyosarcoma, olfactory neuroblastoma, sinonasal undifferentiated carcinoma, and lymphoma. We reviewed precedent literature and further discuss the potential pitfalls to which pathologists may be prone.

Ewing sarcoma

Classification of small round cell tumors of bone is often challenging due to overlapping clinicopathologic features. The purpose of this article is to review the clinical, radiological, histologic, and molecular features of Ewing sarcoma and to provide a discussion of the differential diagnosis of small round cell tumors of bone.

Modern Diagnosis of Small Cell Malignancies of Children

Small cell malignancies of children constitute a continuing diagnostic challenge for surgical pathologists, although modern methods of ancillary diagnosis provide powerful tools that resolve most difficult cases. Current techniques range from identification of DNA alternations, including gene fusions, chromosome translocations, and genetic deletions, to recognition of characteristic patterns of protein expression, usually visualized with immunohistochemistry. In spite of these advances, recognition of key cellular and histologic features remains the keystone of diagnosis but requires adequately fixed and carefully stained histologic sections. Cytologic features now suffice for diagnosis if confirmed by appropriate testing. This article outlines key histologic features of pediatric small cell neoplasms and the algorithms that allow diagnostic confirmation and the initiation of appropriate therapy.

Histological heterogeneity of Ewing's sarcoma/PNET: an immunohistochemical analysis of 415 genetically confirmed cases with clinical support

Ewing's sarcoma (ES)/peripheral neuroectodermal tumor (PNET) are malignant neoplasms affecting children and young adults. We performed a study to typify the histological diversity and evaluate antibodies that may offer diagnostic/prognostic support. In total, 415 cases of genetically confirmed paraffin-embedded ES/PNET were analyzed on whole sections and in tissue microarrays. This study confirms the structural heterogeneity of ES/PNET, distinguishing three major subtypes: conventional ES (280 cases); PNET (53 cases); and atypical ES/PNET (80), including large cells, vascular-like patterns, spindle pattern, and adamantinoma-like configuration. All cases presented positivity for at least three of the four tested antibodies (CD99, FLI1, HNK1, and CAV1). CAV1 appeared as a diagnostic immunomarker of ES/PNET being positive in CD99-negative cases. Hence, the immunohistochemical analysis confirmed the diagnostic value of all four antibodies, which together cover more than 99% of the tumors, independently of the histological variety. The univariate analysis for survival revealed atypical ES as the only histological parameter apparently associated with less favorable clinical outcome, particularly in the subgroup of patients treated with surgery. In conclusion, the diagnosis of atypical ES is a challenge for the pathologist and needs support from molecular techniques to perform an optimal differential diagnosis with other small round cell tumors.

Comparative evaluation of flow-cytometric immunophenotyping and immunocytochemistry in the categorization of malignant small round cell tumors in fine-needle aspiration cytologic specimens

BACKGROUND

The precise diagnosis of malignant small round cell tumors (MSRCTs) in fine-needle aspiration (FNA) cytology is a challenge that requires ancillary investigations. In this study, the authors evaluated the applicability of flow-cytometric immunophenotyping (FCI) and compared it with immunocytochemistry (ICC) for the accurate categorization of MSRCTs.

METHODS

In total, 37 consecutive MSRCTs that had been diagnosed with FNA cytology were analyzed by ICC and FCI using a panel of antibodies against desmin, vimentin, CD99/major histocompatibility class I-related antigen 2, neuron-specific enolase, and pancytokeratin. The final diagnoses included Ewing sarcoma (n = 17), rhabdomyosarcoma (n = 6; 4 embryonal and 2 alveolar subtypes), neuroblastoma (n = 10), desmoplastic small round cell tumor (n = 2), and retinoblastoma (n = 2).

RESULTS

Accurate categorization was possible in 67.5% of cases by ICC and in 64.8% of cases by FCI. Concordant immunophenotyping results with either technique were obtained in 21 cases (59.4%). Low cellularity of the sample and negativity for all markers tested were some limitations to both techniques when applied on fine-needle aspirates. However, using a combination of both techniques, 86.4% (32 of 37 cases) MSRCTs were typed accurately.

CONCLUSIONS

FCI is applicable on FNA material and complements ICC in accurate the typing of MSRCTs. This is particularly useful in advanced-stage disease, when neoadjuvant chemotherapy may be instituted promptly.

Cluster analysis of immunohistochemical profiles in synovial sarcoma, malignant peripheral nerve sheath tumor, and Ewing sarcoma

As a result of overlapping morphologic and immunohistochemical features, it can be difficult to distinguish synovial sarcoma, malignant peripheral nerve sheath tumor, and Ewing sarcoma/primitive neuroectodermal tumor in core biopsies. To analyze and compare immunohistochemical profiles, we stained tissue microarrays of 23 synovial sarcomas, 23 malignant peripheral nerve sheath tumors, and 27 Ewing sarcomas with 22 antibodies potentially useful in the differential diagnosis, and analyzed the data with cluster analysis. Stain intensity was scored as none, weak, or strong. For CD99, tumors with membranous accentuation were independently categorized. Cluster analysis sorted five groups, with like tumors clustering together. Synovial sarcoma clustered into two groups: one cytokeratin and EMA positive (n = 11), the other mostly cytokeratin negative, EMA positive, bcl-2 positive and mostly CD56 positive (n = 9). Malignant peripheral nerve sheath tumor clustered into two groups: one S100 positive, with nestin and NGFR positivity in most (n = 10), the other mostly S100 negative, and variably but mostly weakly positive for nestin and NGFR (n = 11). Ewing sarcomas clustered into a single group driven by membranous CD99 staining. Thirteen cases failed to cluster (outliers), while three Ewing sarcomas clustered into groups of other tumor types. Paired antibodies for each tumor type determined by visual assessment of cluster analysis data and statistical calculations of specificity, sensitivity, and predictive values showed that EMA/CK7 for synovial sarcoma, nestin/S100 for malignant peripheral nerve sheath tumor, and membranous CD99/Fli-1 for Ewing sarcoma yielded high specificity and positive predictive values. Cluster analysis also highlighted aberrant staining reactions and diagnostic pitfalls in these tumors. Hierarchical cluster analysis is an effective method for analyzing high-volume immunohistochemical data.

Expression of the EWS/FLI-1 oncogene in murine primary bone-derived cells Results in EWS/FLI-1-dependent, ewing sarcoma-like tumors

Ewing sarcoma is the second most common malignant pediatric bone tumor. Over 80% of Ewing sarcoma contain the oncogene EWS/FLI-1, which encodes the EWS/FLI-1 oncoprotein, a hybrid transcription factor comprised of NH2-terminal sequences from the RNA-binding protein EWS and the DNA-binding and COOH-terminal regions of the Ets transcription factor FLI-1. Although numerous genes are dysregulated by EWS/FLI-1, advances in Ewing sarcoma cancer biology have been hindered by the lack of an animal model because of EWS/FLI-1-mediated cytotoxicity. In this study, we have developed conditions for the isolation and propagation of murine primary bone-derived cells (mPBDC) that stably express EWS/FLI-1. Early-passage EWS/FLI-1 mPBDCs were immortalized in culture but inefficient at tumor induction, whereas later-passage cells formed sarcomatous tumors in immunocompetent syngeneic mice. Murine EWS/FLI-1 tumors contained morphologically primitive cells that lacked definitive lineage markers. Molecular characterization of murine EWS/FLI-1 tumors revealed that some but not all had acquired a novel, clonal in-frame p53 mutation associated with a constitutive loss of p21 expression. Despite indications that secondary events facilitated EWS/FLI-1 mPBDC tumorigenesis, cells remained highly dependent on EWS/FLI-1 for efficient transformation in clonogenic assays. This Ewing sarcoma animal model will be a useful tool for dissecting the molecular pathogenesis of Ewing sarcoma and provides rationale for the broader use of organ-specific progenitor cell populations for the study of human sarcoma.

Clinical features of molecular pathology of solid tumours in childhood

The outlook for children with cancer has improved substantially over the past 20 years, with over three-quarters of children now surviving in the long term. Better use of existing cytotoxic drugs and supportive care have made large contributions, but some of the improvement in survival is due to a greater knowledge of childhood cancer at the cellular and molecular levels. As in leukaemias, several childhood solid tumours carry balanced chromosomal translocations, resulting in fusion genes that encode chimeric proteins with new oncogenic properties. Many of these fusion genes, and other genetic aberrations are tumour specific and are related to outcome. Tumour biology now plays an important part in identifying appropriate treatment through more accurate diagnoses and new risk stratifications based on molecular markers.

Metastatic neuroblastoma presenting with binocular blindness from intracranial compression of the optic nerves

A 2-year-old boy with blindness as an isolated symptom was found to have no light perception binocularly because of compression of both optic nerves by a neuroblastoma infiltrating the walls of the optic canals and medial sphenoid bone. Imaging disclosed a primary tumor near the kidney and multiple osseous metastases. Although neuroblastoma commonly causes blindness by metastasis to the orbit, it rarely causes bilateral blindness from intracranial compression of the optic nerves. This is the first report of bilateral blindness as the presenting feature.

A systematic review of molecular and biological markers in tumours of the Ewing's sarcoma family

The aims of this study were to perform the first systematic review of molecular and biological tumour markers in tumours of the Ewing's sarcoma family (ESFT), and evaluate the current evidence for their clinical use. A well-defined, reproducible search strategy was used to identify the relevant literature from 1966 to February 2000. Papers were independently assessed for tumour markers used in the screening, diagnosis, prognosis or monitoring of patients with ESFT. Eighty-four papers studying the use of 70 different tumour markers in ESFT's were identified. Low-quality, inconsistent reporting limited meta-analysis to that of prognostic data for 28 markers. Patients with tumours lacking S-100 protein expression have a better overall survival (OS) (hazard ratio (HR)=0.41, 95% confidence interval (CI) 0.19, 0.89) than those with expression; patients with high levels of serum LDH had a worse OS and disease-free survival (DFS) (OS: HR=2.92, CI 2.16, 3.94, DFS: HR=3.38, 95% CI 2.28, 4.99); patients with localised disease and tumours expressing type 1 EWS-FLI1 fusion transcripts had an improved DFS compared with those with other fusion transcript types (HR=0.17, 95% CI 0.079, 0.37). The knowledge base formed should facilitate more informative future research. Improved statistical reporting and large, multicentre prospective studies are advocated.

Hu Immunolabeling as a Marker of Neural and Neuroendocrine Differentiation in Normal and Neoplastic Human Tissues: Assessment Using a Recombinant Anti-Hu Fab Fragment

The recombinant antibody fragment Fab GLN 495 recognizes an epitope shared by members of the neuron-associated Hu protein family (including HuC, HuD, and HelNl). This novel reagent labels the nuclei of neurons throughout the peripheral and central neuraxes and has been shown to recognize pulmonary small cell carcinomas and central nervous system (CNS) tumors of mature neuronal phenotype or neuronogenic differentiating capacity. Using this Fab fragment, we have undertaken a systematic survey of normal human tissues and an assessment of 554 non-CNS tumor samples for immunohistochemical evidence of Hu expression. Adrenomedullary cells, pancreatic islet cells, paraganglial chief cells, isolated adenohypophyseal cells, and spermatogonia were the only nonneuronal normal tissue elements to bind Fab GLN 495. In addition to labeling all 10 small cell carcinomas studied (six of which were extrapulmonary in origin), this recombinant anti-Hu Fab proved immunoreactive with neuroblastomas (four/four), esthesioneuroblastomas (one/one), typical (three/four) and atypical (one/four) pulmonary carcinoids, pancreatic islet cell tumors (two/six), large-cell neuroendocrine carcinoma of lung (one/four), Merkel cell tumors (two/three), medullary carcinomas of the thyroid (four/six), pheochromocytomas (two/four) and paragangliomas (four/four). Nonneural/neuroendocrine tumor labeling was restricted to the neuronal and immature neuroepithelial components of teratomas, to extraskeletal myxoid chondrosarcomas (three/four) and to small subsets of cells within examples of renal rhabdoid tumor (one/four), desmoplastic small cell tumor (one/four), alveolar rhabdomyosarcoma (two/four), Ewing sarcoma/PNET (two/nine), and Wilms tumor (one/four). Immunoreactivity was principally nuclear, with variable cytoplasmic labeling. Our findings support the largely restricted expression of Hu by neural/neuroendocrine neoplasms, suggest a potential role for Fab GLN 495 in the identification of small cell carcinomas irrespective of primary site, and support a recent proposal that at least some extraskeletal myxoid "chondrosarcomas" actually represent neuroendocrine tumors of soft parts. Int J Surg Pathol 8(2):109-117, 2000

PGP9.5: a marker for cellular neurothekeoma

Neurothekeomas are benign, predominantly cutaneous neoplasms that are divided histologically into myxoid, intermediate, and cellular types. Although it is generally agreed that the myxoid type of neurothekeoma has a neural origin, the lack of consistent immunoreactivity to neural markers and insufficient ultrastructural evidence of neural differentiation in cellular neurothekeoma have brought the origin of cellular neurothekeoma into question. In this report the authors show that immunoreactivity to protein gene product 9.5 (PGP9.5)--a broad neural marker--is positive in 100% of cases of cellular neurothekeoma using microwave antigen retrieval, as well as in all cases of myxoid and intermediate neurothekeoma. In contrast, immunoreactivity to S-100 protein is only positive in 3 of 12 cases of cellular neurothekeoma. These results show that PGP9.5 is a useful marker for identifying cellular neurothekeoma, as well as other types of neurothekeomas using the antigen retrieval method. The results are consistent with the notion that cellular neurothekeoma has a neural differentiation.

Adults with Ewing's sarcoma/primitive neuroectodermal tumor: adverse effect of older age and primary extraosseous disease on outcome

OBJECTIVE

To assess outcome and prognostic factors for survival of adults with Ewing's sarcoma/primitive neuroectodermal tumor (PNET).

BACKGROUND

Ewing's sarcoma/PNET is a disease of childhood rarely seen in adults. Accordingly, there is a relative paucity of published literature pertaining to outcome for adults with this disease.

METHODS

Between 1979 and 1996, 37 patients with newly diagnosed Ewing's sarcoma/PNET were evaluated and treated at the Adult Sarcoma Program at Dana-Farber Cancer Institute and Brigham & Women's Hospital. Twenty-six patients had localized disease at presentation and 11 had metastatic disease. All but two patients received multiagent chemotherapy. Local treatment consisted of surgery (7 patients), surgery and radiation therapy (19), radiation therapy (6), or no local treatment (5). Median follow-up for living patients was 100 months (range 8 to 199).

RESULTS

The 5-year survival rate for the group overall was 37%+/-9%. The 5-year local control rate was 85%+/-7%. Significant favorable predictors for survival on univariate analysis included localized disease at presentation, primary origin in bone, primary size <8 cm, and a favorable objective response to chemotherapy. Patients with localized disease had a 5-year survival rate of 49%+/-11% compared with 0% for those with metastatic disease at presentation. Multivariate analysis showed three significant independent predictors for death: metastatic disease at presentation, primary origin in extraosseous tissue versus bone, and age 26 years or older.

CONCLUSION

Adult patients with Ewing's sarcoma/PNET at highest risk for death are those who are older than 26 years and have metastatic disease or an extraosseous primary tumor. The development of novel therapies should target these high-risk groups.

Ewing's sarcoma of os calcis: case report with a review of literature

A rare case of Ewing's sarcoma of os calcis is described here. Its atypical clinical and radiological features often delay the diagnosis. These features and review of literature are discussed.

Oral granular cell tumours: a histological and immunocytochemical study

In a series of nine cases of intra-oral granular cell tumors (GCTs) an attempt was made, using both histochemical and immunocytochemical methods, to determine whether these tumours show Schwann-cell or neuroendocrine differentiation. Positive immunostaining with protein gene product 9.5 (PGP 9.5), neurone-specific enolase (NSE) and S-100, in contrast to predominantly negative immunostaining in 12 cases of neurilemmoma of the head and neck, and a similar pattern of staining with luxol fast blue to five known neuroendocrine tumours, strongly suggests that granular cell tumors may be neuroendocrine in nature.

Primitive neuroectodermal tumour of the chest wall

The concept of primitive neuroectodermal tumour (PNET) has been evolving for many years, as has its nomenclature. It was first described as a tumour arising in peripheral nerve, when it was called neuroepithelioma. These tumours are part of the differential diagnosis of malignant small round cell tumours, which include Ewing's sarcoma, rhabdomyosarcoma, neuroblastoma and lymphoma, and which appear as sheets of monotonous small round cells on light microscopy, staining dark blue with haematoxylin and eosin. In the 1970's, reports of tumours displaying neural features introduced new terms such as primitive neuroectodermal tumour and peripheral neuroectodermal tumour. A relationship to the undifferentiated primitive neuroectodermal tumours of the central nervous system in children was assumed by the title of these tumours, although it was recognised that they were not necessarily related to peripheral nerves.

Immunocytochemical study of 12E7 in small round-cell tumours of childhood: an assessment of its sensitivity and specificity

12E7 is a monoclonal antibody to the MIC2 gene product and can be applied to formalin-fixed, paraffin-embedded tissue. The diagnostic utility of 12E7 as a marker of Ewing's sarcoma and peripheral neuroectodermal tumour was assessed. Immunocytochemical studies were performed on 120 small round-cell tumours from children and adolescents. Immunoreactivity for 12E7 was seen in 13 of 15 Ewing's sarcomas. 14 of 15 peripheral neuroectodermal tumours, four of 14 embryonal rhabdomyosarcoma, seven of 11 T-lymphoblastic lymphomas and one T-cell acute lymphoblastic leukaemia. Immunoreactivity was located on the cell-membrane of Ewing's sarcomas, peripheral neuroectodermal tumours and lymphoid tumours while rhabdomyosarcomas showed weak, cytoplasmic staining in differentiated rhabdomyoblasts. Studies on alveolar rhabdomyosarcomas (n = 10), acute myeloid leukaemias (3), B-lymphoblastic lymphomas (8), blastema-rich nephroblastomas (9), neuroblastomas (20) and retinoblastomas (10) as well as single examples of B-cell acute lymphoblastic leukaemia, Ki-1 anaplastic lymphoma of indeterminate phenotype and intra-abdominal desmoplastic tumour with divergent differentiation were negative. 12E7 is a sensitive marker for the Ewing's sarcoma/peripheral neuroectodermal group of tumours and is useful in distinguishing them from neuroblastoma and blastema-rich nephroblastoma. However, immunopositivity for 12E7 should be interpreted in conjunction with the results of neural and lymphoid markers.

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.

Divergent differentiation in small round-cell tumours of the soft tissues with neural features--an analysis of 10 cases

A series of 10 small round-cell tumours, having in common evidence of neural differentiation, were investigated by immunohistochemistry and electronmicroscopy. In seven, evidence of divergent muscle and/or epithelial differentiation was found. This phenomenon thus appears more common than previously appreciated and suggests that there may be a continuous and overlapping phenotypic spectrum from Ewing's tumour of soft tissue to intra-abdominal desmoplastic small cell tumour.

Prognostic implication of immunodetection of P glycoprotein in Ewing's sarcoma

Increased expression of P glycoprotein is associated with multidrug resistance in many cell lines. P glycoprotein has been detected in different human tumors. To assess the implication of multidrug resistance in the prognosis of Ewing's sarcoma the expression of P glycoprotein was studied immunohistochemically in pre- and post-therapeutic tumor tissues of 21 cases treated according to the CESS 81 or 86 protocol. The response to chemotherapy was evaluated histologically. Formalin-fixed, paraffin-embedded and fresh frozen sections were immunostained with a monoclonal antibody to P glycoprotein, clone JSB 1, using the double APAAP method. P glycoprotein was detected in 12 cases of 21 (57%) in either pre- or postchemotherapy tumor tissues. From the 21 cases 8 revealed a good morphological response to chemotherapy (33%); 10 of the 13 non-responders were positive for P glycoprotein (77%), but only 2 of the 8 responders (25%). The difference was statistically significant (P < 0.05). Comparing P glycoprotein expression with the clinical outcome, we found that 7 of 12 positive cases had died (58%). From the negative cases only 3 of 9 had died (33%). However, judged by the Kaplan Meyer life tables, these data were not significant. In conclusion our results suggest that the immunodetection of P glycoprotein indicates a poor response to chemotherapy and probably a bad clinical outcome for Ewing's sarcoma patients.

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.

'Neuron-specific' protein gene product 9.5 (PGP 9.5) is also expressed in glioma cell lines and its expression depends on cellular growth state

Protein gene product 9.5 (PGP 9.5), which in the normal nervous system is restricted to certain neurons, has been detected in two glioma cell lines, rat C6 and human GL15, by immunoblotting and immunocytochemistry. Its expression in these cells depends on the cellular growth state, being maximal between the first and second post-plating day. Only a faint PGP 9.5 immunoreactivity can be observed in glioma cells after the eleventh post-plating day, i.e. about one week after confluency has been reached. The present results suggest that PGP 9.5 in cultured glial cells is maximally expressed during the growth phase and that the protein could play a role during brain development in glial cells, in reactive gliosis, or in tumorigenesis of the glial lineage.

Immunohistochemical staining for ferritin in neuroblastomas

Immunohistochemical staining for ferritin was examined in 35 neuroblastomas from 27 children and compared with serum ferritin levels. All but two of the patients presented with advanced (stages III and IV) disease, and the adrenal was the most common primary site (20/27, 74%). Immunostaining was positive in only one of 14 tumour biopsies taken at the time of diagnosis (7%), but eight of 21 neuroblastomas (38%) marked for ferritin after chemotherapy. No consistent association was established between tumour- and serum-associated ferritins in the untreated or treated groups. Ferritin staining in treated neuroblastomas was usually more marked in partly differentiated tumour cells. The increased frequency of ferritin positive neuroblastomas after chemotherapy appeared to be associated with large local accumulations of ferritin and haemosiderin within the treated tumours, and (probably) with the blood transfusions which these children received.

Cytogenetic and molecular characterization of a newly established neuroblastoma cell line LS

A new human neuroblastoma cell line (LS) that originated from an abdominal tumor of a 16-month-old girl is presented; it was classified, according to Evans, as being stage III. Morphological (dense-core particles) and biochemical characteristics (dopamine-beta-hydroxylase, acetylcholinesterase, neuron-specific-enolase) confirmed the diagnosis. In addition to a slightly variable modal chromosome number of 48 or 49 (because of marker-chromosomes and autosomal trisomies), cytogenetic analysis revealed two constantly appearing chromosomes with homogeneously stained regions (HSR's). The karyotype remained constant over 50 passages in vitro [49,XX, -12, +der5, + 17, + mar1, + mar2]. Double minutes were a rare phenomenon and appeared only in a few metaphases. In situ hybridization showed that some of the HSR's consisted of amplified N-myc copies. The distribution of the N-myc copies according to in situ hybridization signals along the HSR's was compared with the data of Southern and Northern blotting analyses.

NB84: a new monoclonal antibody for the recognition of neuroblastoma in routinely processed material

A new monoclonal antibody NB84 recognizing an uncharacterized molecule of 57 kD was produced using human neuroblastoma tumour tissue as a source of antigen. The antibody was selected for its ability to give reliable staining on conventional formalin-fixed, paraffin-embedded material. In the present study, NB84 was assessed for its usefulness in the differential diagnosis of paediatric small cell tumours. It gave reliable staining of 17/19 (90 per cent) neuroblastomas and was negative on all other tumours apart from Ewing's sarcomas, of which 9/14 (64 per cent) showed mainly focal positivity. It is concluded that in association with a panel of markers against leucocyte, muscle, epithelial, and neural markers NB84 provides considerable assistance in the recognition of neuroblastoma and thus is important in enabling the most appropriate therapy to be given.