Diagnostic utility of FLI-1 monoclonal antibody and dual-colour, break-apart probe fluorescence in situ (FISH) analysis in Ewing's sarcoma/primitive neuroectodermal tumour (EWS/PNET). A comparative study with CD99 and FLI-1 polyclonal antibodies

Primary intracranial Ewing sarcoma/ peripheral primitive neuroectodermal tumor, an entity of unacquaintance: a series of 8 cases

PURPOSE

The purpose is to highlight the primary intracranial (meningeal-based) occurrence of Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET).

METHODS

This report is a collation of clinicopathological features of eight cases of molecularly and clinicoradiologically confirmed primary (non-metastatic) intracranial (non-osseous) meningeal ES/PNET.

RESULTS

The age range was 1 to 33 years with a median age of 9 years. Male to female ratio was 0.6:1. All patients were diagnosed on the debulking surgical material (gross total resection, 2 cases; subtotal resection, 6 cases) and showed primitive embryonal histomorphology with diffuse membranous CD99 immunoexpression and EWSR1 gene rearrangement by fluorescence in situ hybridization. Seven of them showed a typical FISH pattern of split signals with break-apart probe, while one showed an unusual signal pattern of loss of green signals. EFT-2001 adjuvant protocol was followed along with focal radiotherapy (RT) in all cases (except case 8, full course of chemotherapy could not be completed). Two cases had local recurrence-one of them died of disease recurrence before the administration of further treatment.

CONCLUSION

This series adds non-osseous intracranial site to the list of uncommon sites of occurrence for ES/PNET and more importantly emphasizes the need to be considered in a differential list of primary intracranial primitive embryonal tumors before embarking as primary central nervous system (CNS) embryonal tumor, NOS.

A case report of neonatal orbital peripheral primitive neuroectodermal tumor and literature review

Primitive neuroectodermal tumors are rare malignant neoplasms from primitive neural crest cells. Most primitive neuroectodermal tumors occur in the central and sympathetic nervous systems. We report a Chinese newborn patient presenting a huge unilateral proptosis after birth, diagnosed as orbital peripheral primitive neuroectodermal tumor by histopathology and immunohistochemistry. Our case is the first reported case of orbital peripheral primitive neuroectodermal tumor diagnosed in the newborn period. The clinical manifestations, radiological findings, histopathologic, and immunohistochemistry results are described in detail. We also conducted a literature search focusing on primitive neuroectodermal tumor of the orbit. To the best of our knowledge, all articles with English abstracts were reviewed here.

Extraskeletal Ewing's sarcoma/peripheral primitive neuroectodermal tumor of the small bowel presenting with gastrointestinal perforation

Extraskeletal Ewing’s sarcoma (E-EWS)/peripheral primitive neuroectodermal tumor (pPNET) is a rare soft tissue tumor that arises from a multipotent progenitor cell and is considered to be of neuroectodermal origin. Although soft tissue E-EWS/pPNETs are common, they are exceedingly rare in the small bowel. Only 30 cases of E-EWS/pPNET of the small bowel have been reported. However, only one case of gastrointestinal perforation has been reported till today. Here, we report the second case of E- EWS/pPNET with gastrointestinal perforation.

Ovarian primary primitive neuroectodermal tumor: a review of cases at PUMCH and in the published literature

Background

The pathological characteristics, treatment strategies and prognosis of ovarian primary primitive neuroectodermal tumor (PNET) were unclear due to the rarity of PNET. All cases treated at Peking Union Medical College Hospital (PUMCH) between 1975 and 2016 and published in the English literature between 1980 to 2017 were reviewed.

Results

Finally four cases from PUMCH and 15 cases in the literature were included. The median age was 25 years (range 13–79), and the median diameter of the tumors was 13.4 cm (range 5.0–30.0). The most common initial symptoms were abdominal pain, bloating and a pelvic mass. Diagnosis primarily depended on immunohistochemical and fluorescence in situ hybridization data. Treatment consisted of surgery, various chemotherapy regimens and/or radiotherapy. The 5-year overall survival (OS) and progression-free survival (PFS) rates were 15 and 52%, respectively. For patients with OS and PFS > 12 months, the median ages were 21 years (range 13–35) and 17 years (range 13–35), respectively, while for patients with OS < 12 months and PFS < 12 months, the median ages were 48 years (range 14–79) and 25 years (range 18–79), respectively.

Conclusions

No standard therapy for ovarian primary PNET exists, and an individualized strategy is recommended. Young patients seem to have better prognoses.

A mesenteric primary peripheral Ewing's sarcoma/primitive neuroectodermal tumor with molecular cytogenetic analysis: Report of a rare case and review of literature

Rare cases of Ewing's sarcoma/primitive neuroectodermal tumors (EWS/PNETs) arising from mesenteric tissue have been reported. This report describes an EWS/PNET in a 25-year-old woman who presented with abdominal pain lasting 3 days. Radiologic evaluation revealed a 9 cm × 6 cm homogeneous mass in the lower abdomen with homogeneous enhancement and invasion of the ileum. Surgical resection was completed during exploratory laparotomy. Immunohistochemically, the tumor cells revealed CD99, friend leukemia virus integration-1 and NKX2.2 (NK2 Homeobox 2, a protein coding gene) and subsequently showed EWSR1 rearrangement. The histological feature, immunohistochemical results and genetic fluorescence in situ hybridization analysis of this case were confirming the diagnosis of EWS/PNET. Adjuvant chemotherapy was suggested, but the patient was lost to follow-up.

EWSR1 Rearrangement and CD99 Expression as Diagnostic Biomarkers for Ewing/PNET Sarcomas in a Moroccan Population

Ewing sarcoma/primitive neuroectodermal tumor (Ewing/PNET sarcomas or EPS) are a group of round cell tumors. Malignant round cell tumors form a large and diverse group that includes rhabdomyosarcoma, synovial sarcoma, non-Hodgkin's lymphoma, neuroblastoma, hepatoblastoma, Wilm's tumor, desmoplastic small round cell tumor, and other morphologically similar entities. Differential diagnosis of Ewing sarcoma/primitive neuroectodermal tumor (Ewing/PNET sarcomas or EPS) is difficult. In addition to morphology and immunohistochemistry (IHC), differential diagnosis of these tumors is based on molecular analysis of the EWSR1 gene rearrangement using fluorescent in situ hybridization (FISH) technique. We investigated the diagnostic value of combined CD99 immunostaining and EWSR1 t(22q12) alteration using a dual-color, break-apart rearrangement probe in forty-one formalin-fixed paraffin-embedded (FFPE) tissue samples from pediatric and adult patients diagnosed with EPS. IHC was performed in all cases using the CD99 antibody and showed a positivity of 92.7% in the enrolled cases (38/41) followed by FISH analysis where 48.8% of the cases (20/41) were rearranged. Sensitivity and specificity for IHC assays were 88% and 58%, respectively. Notably, FISH had a sensitivity of 100% and a specificity of 87%. In addition, CD99 positivity was found to correlate with EWSR1 rearrangement (p < 0.05). This report shows that FISH has better sensitivity and specificity than IHC in the Moroccan population, and supports its combination with CD99 immunostaining as diagnostic biomarkers for this rare malignant entity."

Ewing's Sarcoma/Peripheral Primitive Neuroectodermal Tumors in Bronchus

Ewing sarcoma/peripheral primitive neuroectodermal tumors (ES/pPNET), a member of the Ewing sarcoma family of tumors, is a malignant soft tissue tumor with small undifferentiated neuroectodermal cells. Primary trachea-bronchial ES/pPNET is very rare. The most common pulmonary ES is due to a metastasis. We describe a case of ES/pPNET which originated in the left basal trunk bronchus. The patient was a 30-year-old male, presenting with irritable cough and fever for 10 days. A tumor of 60 mm in diameter was found in the left basal trunk bronchus, extending to the left lower lobe. No distant metastases were detected. Histopathological examination revealed a malignancy of ES/pPNET with a diffuse proliferation of round cells, a Flexner-Wintersteiner rosette formation and positive staining for CD99. The patient was successfully treated with a combination of left lower lobectomy and adjuvant chemotherapy and has remained disease-free for approximately 18 months at follow-up. This case highlights that ES/pPNET should be considered as a differential diagnosis in cases of trachea-bronchial tumors.

Primary Ewing's Sarcoma of Cranium in a Pediatric Patient

Ewing's sarcoma primarily involving the skull is an unusual occurrence (1% of all Ewing's sarcoma cases) with very few reported cases in the published literature. The challenge in such cases is to establish a definitive diagnosis before starting the multidisciplinary treatment approach. We report such a rare case in a 13-year-old boy who is being treated at our institute with an intention of adding to the limited information we currently have on diagnosis, management, and the outcome of such cases.

Meningeal Ewing Sarcoma/Peripheral PNET: Clinicopathological, Immunohistochemical and FISH study of four cases

Meningeal Ewing Sarcoma (ES)/peripheral primitive neuroectodermal tumor (pPNET) is a rare diagnostically challenging small round cell tumor in the CNS. This study investigates the clinical pathological features of four cases of this tumor from archives of 6 years in our hospital. Patients were within the median age of 21.5 years and male to female ratio was 1:1. The tumors distributed at the supra-tentorial location, posterior fossa and lumbar vertebral canal, usually presenting as the dura-sited nodule or having close connection with the meninges within the cranium or vertebral canal. Histopathologically, small round undifferentiated tumor cells with hypercellularities, scant cytoplasm and inconspicuous nucleoli were observed, although some components such as atypical larger vesicular nuclei, prominent nucleoli of tumor cells, necrotic foci and mesenchymal collagen proliferation forming the lobular structure, were also appreciated. Immunohistochemally, tumor cells displayed membranous positivity of CD99 (4/4), nuclear positivity of FLI-1 (4/4) and NKX2.2 (4/4), negativity of EMA, GFAP and synaptophysin expression. The histochemical PAS staining showed weak positivity in one case. Fluorescence in situ hybridization (FISH) test using EWSR1 (22q12) dual color break apart rearrangement probe showed positive results in two cases. Results suggest that using a panel of immunohistochemical markers, including NKX2.2, CD99, FLI-1, EMA, GFAP and synaptophysin, combined with the supplementary EWSR1 FISH test, helps to define the diagnosis of meningeal ES/pPNET of CNS.

Atypical teratoid/ rhabdoid tumor, an immunohistochemical study of potential diagnostic and prognostic markers

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare tumor of the CNS mostly seen in infants and is often associated with a dismal outcome. Despite the heterogeneous morphology and/or immunoprofile, its diagnosis nowadays relies on the negative INI-1/BAF47 nuclear immunostain in tumor cells. We aim to investigate a number of immunohistochemical antibodies as potential diagnostic and prognostic markers. All AT/RT cases in patients younger than 18 years of age were included. Demographics, clinical features and outcome were collected. Immunostains tested included SALL-4, OCT3/4, CD99, FLI-1, cyclin-D1, β-catenin, P53, P16, CDX2 and WT-1. Nineteen cases (10 males) were identified at our center between 2004-2013 with a median age of 24 months. Ten (52.6%) cases were supratentorial. Six (42.9%) cases showed metastasis at time of presentation. Chemotherapy was administered to 10 (62.5%) and radiotherapy to seven (43.8%). The median overall survival was 11 months. A single long-term survival of 104 months was identified. Pathologically, most cases showed an admixture of rhabdoid cells and/or small cells and/or pale cells in variable proportions. Of all tested antibodies, only positivity for FLI-1 was associated with improved survival (P = 0.0012), while positivity for cyclin-D1 showed a trend toward improved survival (P = 0.0547). CDX2 was positive only in the single long-term survival. Interestingly, two cases showed co-expression of CD99 and FLI-1, and some were positive for SALL-4. In conclusion, FLI-1 and cyclin-D1 are potential prognostic markers associated with better outcome. Occasional AT/RT cases might co-express CD99 and FLI-1 as well as SALL-4, a potential diagnostic pitfall with Ewing sarcoma/ primitive neuroectodermal tumors and germ cell tumors, respectively.

Clinical presentation and long-term outcome of primary spinal peripheral primitive neuroectodermal tumors

Primary spinal peripheral primitive neuroectodermal tumors (pPNETs) are extremely rare entities that predominantly occur in children and young adults. Few studies have reported more than three cases. There are no current optimum treatment strategies due to the paucity of data. Here, we present 13 patients (nine females and four males) with primary intraspinal pPNETs who were surgically treated from April 2008 to February 2014. Histopathologic findings revealed the expression of CD99 in all cases. Limb weakness was the most common initial symptom (11/13, 85 %). The tumors were located mainly at the cervical level (6/13, 46 %) and in the epidural space (10/13, 77 %). The radiological diagnosis was neurinoma or meningioma in most cases (10/13, 77 %). Gross total resection was achieved in 77 % (10/13) of patients. During a mean follow-up of 25.5 months, local relapse occurred in 8 (61.5 %) patients and distant metastases occurred in 8 (61.5 %) patients. The overall 1-year survival rate was 77 % (10/13), and the overall 2-year survival rate was 54 % (7/13). The 2-year survival rate was 57.1 % in patients with adjuvant chemotherapy and 50 % in those without chemotherapy. Gross total resection and adjuvant radiotherapy with or without chemotherapy demonstrated a longer survival period (1-year survival rate: 100 %; 2-year survival rate: 86 %). Our data showed that primary spinal pPNETs are extremely rare and aggressive tumors with a poor prognosis. Radical resection is advocated. Gross total resection combined with adjuvant radiation may help to significantly improve patient survival period. Chemotherapy may also help to slightly prolong patient life.

Upregulation of NKX2.2, a target of EWSR1/FLI1 fusion transcript, in primary renal Ewing sarcoma

Renal Ewing sarcoma (ES) is a rare malignant tumor characterized by fusion of the EWSR1 gene with a member of the ETS family of oncogenes, arising at a specific chromosomal translocation. Diagnosis of ES can be problematic, especially from cytological or small bioptical specimens because the differential diagnoses comprising a diverse group of small round blue cell tumors (SRBCTs). We report a case of primary renal ES in a young male, which had a t(11;22) (q24;q12) chromosome translocation encoding a type2 EWSR1/FLI1 fusion transcript. The tumor cells showed diffuse cytoplasmic immunoreactivity for CD99 and diffuse nuclear immunoreactivity for NKX2.2, an important oncogenic transcriptional target of EWSR1/FLI1, not only in the histological, but also in the cytological specimens. From the results of this case, we speculate that NKX2.2, in combination with CD99, may be a useful immunocytochemical marker to distinguish renal ES from other SRBCTs of kidney.

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.

Diagnostic Immunohistochemistry in Cutaneous Neoplasia: An Update

Immunohistochemistry (IHC) is an important adjunct in the diagnosis of neoplastic skin diseases. In addition to the many established IHC markers currently in use, new markers continue to emerge, although their general acceptance and routine application requires robust validation. Here, we summarize the most well-established and commonly used biomarkers along with an array of newer ones reported in the past several decades that either demonstrate or hold high clinical promise in the field of cutaneous pathology. We also highlight recent applications of novel IHC markers in melanoma diagnosis including genetic mutation status markers [e.g. BRAF (v-raf murine sarcoma viral oncogene homolog B) and NRAS (neuroblastoma RAS viral oncogene homolog)] and an epigenetic alteration marker (e.g. 5-hydroxymethylcytosine). We specifically focus on the role of IHC in the differential diagnosis of cutaneous lesions that fall under the following categories: melanoma, epidermal tumors with an intraepidermal epitheliomatous pattern, spindle cell lesions of the dermis, small round blue cell tumors of the dermis, and cutaneous adnexal tumors. While IHC is a valuable tool in diagnostic dermatopathology, marker selection and interpretation must be highly informed by clinical context and the histologic differential diagnosis. With rapid progress in our understanding of the genetic and epigenetic mechanisms of tumorigenesis, new IHC markers will continue to emerge in the field of diagnostic dermatopathology.

Primary primitive neuroectodermal tumor arising in the mesentery and ileocecum: A report of three cases and review of the literature

Primitive neuroectodermal tumor (PNET) is most commonly encountered in the soft tissue or bone in children and young adults, and its involvement in the intestines is exceedingly rare. To the best of our knowledge, eighteen cases have been reported to date. The present study reports three cases of PNET arising in the mesentery and ileocecum in 59- and 22-year-old males and a 36-year-old female. Computed tomography revealed a solid mass in the lower abdomen, with areas of cystic changes. Microscopically, the tumors were composed of small round cells arranged in sheets and rosettes with scant cytoplasm, hyperchromatic nuclei and a high mitotic rate. The tumor cells were immunopositive for CD99 and FLI1. EWS/FLI1 translocations were detected in all cases. Case 1 and case 2 underwent tumor resection without any preoperative radiotherapy, chemotherapy or biological therapy. Case 3 underwent tumor resection and received eight cycles of IAP chemotherapy (2.0 mg ifosfamide, 80 mg epirubicin, 30 mg cisplatin 30mg). Case 3 was followed up for 34 months until they succumbed to peritoneal recurrence, whereas the other cases were not followed up. The incidence of these small round-cell tumors in the intestinal system, their clinical and pathological features and differential diagnosis are discussed with a review of the literature.

[Value of core needle biopsy in preoperative diagnostics of soft tissue tumors: possibilities and limitations]

The differential diagnosis of soft tissue swellings encompasses a variety of benign, intermediate, low-grade malignant and high-grade neoplastic lesions in addition to tumor-like reactive processes. As treatment of these heterogeneous conditions varies greatly from conservative observation and simple local excision up to extensive radical surgical resection, treatment decisions are based mainly on a precise preoperative histological diagnosis on limited biopsy material. Even for clinically unequivocal sarcomas, the importance of the preoperative histological diagnosis has been increasingly emphasized as different therapeutic regimens have been established for different sarcoma types and the indications for preoperative treatment is influenced by the tumor grade and by the entity itself. Other factors positively influencing the increasing use of core needle biopsy for preoperative tumor diagnosis in soft tissue pathology are the availability of modern high-resolution imaging modalities as well as the establishment of several new second generation immunohistochemical markers and the discovery of entity-specific translocations detected by fluorescence in situ hybridization (FISH) in several sarcoma subtypes. In this review it will be shown that a targeted approach for processing core needle biopsies oriented towards the characteristic topographical, demographic, cytomorphological and architectural features of soft tissue lesions facilitates a precise diagnosis of soft tissue neoplasms in most cases. However, profound knowledge of the different aspects of soft tissue tumor diagnostics and familiarity with the frequent as well as the less common and rare tumor entities and variants is a prerequisite for appropriate interpretation of core needle biopsy findings and for selecting a limited but well-suited marker panel. The utilization of modern immunohistochemistry and/or FISH methods is highly useful for establishing the diagnosis of rare and unusual neoplasms in core needle biopsies.

Primitive neuroectodermal tumor presenting with diffuse leptomeningeal involvement in a 55-year-old woman: a case report and brief summary of current diagnostic tests and treatment

Primitive neuroectodermal tumors (PNETs) are typically present as masses in children and adolescents, but rarely in adults. Diagnoses, management strategies, and prognostication factors are not well established in adult cases of PNETs. We describe the case of a central nervous system PNET diagnosed in a 55-year-old woman presenting with a sudden onset of symptoms consisting of increased intracranial pressure and findings of diffuse leptomeningeal enhancement and a small medullary lesion seen on MRI. Amongst the small database of PNETs diagnosed in adults, our case report stands out as one of few cases describing a primarily leptomeningeal PNET diagnosed on biopsy. We also review the literature on PNETs presenting with diffuse leptomeningeal disease and the treatment of PNETs in the adult population.

The small round blue cell tumors of the sinonasal area: histological and immunohistochemical findings

Background

Primary Small round blue cell tumors (SRBCT) in sinonasal comprise histogenetically diverse entities with overlapping morphologic features. Because of the limited initial biopsy tissue materials, differential diagnostic difficulties may arise, and as they have different management, exact diagnosis and classification are very important.

Objectives

In this study, we analyzed the immunohistochemical expression of a panel of markers in the classification and diagnosis of sinonasal SRBCTs.

Material and Methods

This cross sectional study was performed on 36 paraffin embedded tissue samples. Histologic and immunohistochemical slides from 36 patients with SRBCT were analyzed retrospectively. The patients were admitted in Khalili hospital, Shiraz from 1383 to 1388.

Results

There were 13 women and 23 men with the mean age of 53 ±12.1. There were 9 malignant melanoma, seven poorly differentiated SCC; six lymphoma (DLBL); 4 SCNEC; three SNUC; two ON; two Ewing/PNET; two embryonal rhabdomyosarcoma, and one plasmacytoma. Pan-cytokeratin was strongly expressed poorly differentiated SCC and all cases of SNUC. Coexpression of desmin and nuclear myoD1 was only detected in rhabdomyosarcoma. HMB45 was only expressed in sinonasal melanoma. CD99 expression was identified only in Ewing/PNET. FLI-1 was detected in 50% of PNET. P63 was expressed in poorly differentiated SCC (2/7) and SNUC (1/3).

Conclusions

The results of our study indicate that the integration of histopathologic findings with application of limited but highly specific markers led to the separation of carcinomas, lymphoma and melanomas from other small cell tumors. Using a panel of keratin, LCA, desmin, and HMB45 is the most practical and economic approach to accurately classify these tumors.

Usefulness of a monoclonal ERG/FLI1 antibody for immunohistochemical discrimination of Ewing family tumors

Ewing family tumors (EFTs) and prostate carcinomas are characterized by rearrangement of ETS genes, most commonly FLI1 (EFTs) and ERG (prostate carcinomas). Previously, we characterized an antibody against ERG (EPR3864) for detecting ERG-rearranged prostate carcinoma. Because EPR3864 also cross-reacts with FLI1, we evaluated the usefulness of EPR3864 for discriminating EFTs from other small round blue cell tumors (SRBCTs) with immunohistochemistry. Of 57 evaluable EFTs, 47 (82%) demonstrated at least moderate, diffuse, nuclear ERG/FLI1 staining (including 89% and 100% of cases with confirmed EWSR1:FLI1 and EWSR1:ERG fusions, respectively), of which 1, 3, and 43 showed negative, cytoplasmic, or membranous CD99 staining, respectively. Among other SRBCTs (61 cases, 7 types), at least moderate, diffuse, nuclear EPR3864 staining was seen in all precursor B-lymphoblastic lymphomas/leukemias and subsets of Burkitt lymphomas (10%) and synovial sarcomas (45%). In summary, EPR3864 may be useful in detecting EWSR1:FLI1 and EWSR1:ERG rearranged EFTs in addition to prostate carcinomas.

Molecular diagnostics complementing morphology in superficial mesenchymal tumors

Molecular techniques are increasingly important in the practice of surgical pathology. In soft tissue tumors, there are a number of tumors with recurring cytogenetic abnormalities. Knowledge of these abnormalities has furthered our understanding of these tumors and has also allowed development of molecular techniques to aid in the diagnosis. This review will focus on mesenchymal tumors with specific cytogenetic abnormalities that may present as a superficial tumor of the dermis or subcutis.

Expression of ERG, an Ets family transcription factor, identifies ERG-rearranged Ewing sarcoma

ERG gene encodes for an Ets family regulatory transcription factor and is involved in recurrent chromosomal translocations found in a subset of acute myeloid leukemias, prostate carcinomas and Ewing sarcomas. The purpose of this study was to examine the utility of an ERG antibody to detect EWSR1-ERG rearranged Ewing sarcomas. A formalin-fixed paraffin-embedded tissue microarray and whole-tissue sections from 32 genetically characterized Ewing sarcomas were examined: 22 with EWSR1-FLI1, 8 with EWSR1-ERG and 2 with EWSR1-NFATC2. Immunohistochemistry was performed using a rabbit anti-ERG monoclonal antibody directed against the C-terminus of the protein and a mouse anti-FLI1 monoclonal antibody against a FLI1 Ets domain (C-terminus) fusion protein. Immunoreactivity was graded for extent and intensity of positive tumor cell nuclei. ERG labeling was seen in 7/8 EWSR1-ERG cases (predominantly diffuse (5+), moderate to strong), while only 3/24 non-EWR1-ERG cases showed labeling (very weak). FLI1 labeling was observed in 29/31 cases regardless of fusion variant; 23 displayed diffuse (5+) strong/moderate labeling (5/7 EWSR1-ERG, 18/22 EWSR1-FLI1). Both EWSR1-NFATC2 cases had weak reactivity with FLI1 and weak or no reactivity for ERG. In conclusion, strong nuclear ERG immunoreactivity is specific for Ewing sarcomas with EWSR1-ERG rearrangement. In contrast, FLI1 was not specific to rearrangement type, likely because of cross reactivity with the highly homologous Ets DNA-binding domain present in the C-terminus of both ERG and FLI1.

Immunohistochemical endothelial markers: a review

A relatively large number of new endothelial markers that can assist in the diagnosis and classification of endothelial and vascular neoplasms have become available over the past few years. The expression of these markers, however, differs considerably among the various tumors. A selection of markers that have potential diagnostic utility or are of current interest among pathologists are reviewed and compared with some of the more traditional markers that have been employed in diagnostic pathology.

Small Round Cell Tumors of Bone

Diagnosing small round cell tumors (SCRTs) can be a difficult task for pathologists due to overlapping clinicopathologic features. This review highlights the clinical, radiographic, histologic, immunohistochemical, and genetic features of the most common SRCTs involving bone with an emphasis on differential diagnosis. SRCTs are a heterogeneous group of neoplasms characterized by poorly differentiated cells with small, blue, round nuclei and scant cytoplasm. They can occur as primary tumors in bone or soft tissue.

Ewing sarcoma/peripheral primitive neuroectodermal tumor and related tumors

Ewing sarcoma/peripheral primitive neuroectodermal tumor (EWS/pPNET) and other tumors with EWS gene rearrangements encompass a malignant and intermediate neoplasm with a broad anatomic distribution and a wide age range but a predilection for soft tissue in children, adolescents, and young adults. The overlapping histologic, immunohistochemical and cytogenetic and molecular genetic features create diagnostic challenges despite significant clinical and prognostic differences. Ewing sarcoma is the 3rd most common sarcoma in children and adolescents, and desmoplastic small round cell tumor is a rare neoplasm that occurs more often in older children, adolescents, and young adults. Pathologic examination is complemented by immunohistochemistry, cytogenetics, and molecular genetics. This article reviews the clinicopathologic features of EWS/pPNET and desmoplastic small round cell tumor in the spectrum of tumors with EWS gene rearrangements. Other tumors with different histopathologic features and an EWS gene rearrangement are discussed elsewhere in this volume.

Primitive neuroectodermal tumors of the spine: a comprehensive review with illustrative clinical cases

Primary spinal primitive neuroectodermal tumors (PNETs) are uncommon malignancies that are increasingly reported in the literature. Spinal PNETs, like their cranial counterparts, are aggressive tumors and patients with these tumors typically have short survival times despite maximal surgery, chemotherapy, and radiation. Because no standard management guidelines exist for treating these tumors, a multitude of therapeutic strategies have been employed with varying success. In this study the authors perform a comprehensive review of the literature on primary spinal PNETs and provide 2 new cases that highlight the salient features of their clinical management.

Heterologous and rare homologous sarcomas of the uterine corpus: a clinicopathologic review

Pure sarcomas of the uterine corpus are uncommon, constituting less than 3% of all malignancies at this site, and most of them are leiomyosarcomas and endometrial stromal sarcomas. Rare histotypes of homologous sarcomas and heterologous sarcomas are occasionally encountered, and the absence of significant accumulated experience with these histotypes at this location may potentially raise diagnostic and patient management difficulties. In this article, the clinicopathologic attributes of all earlier reported sarcomas of the uterine corpus other than leiomyosarcomas and endometrial stromal sarcomas are summarized. Included are embryonal rhabdomyosarcoma, pleomorphic rhabdomyosarcoma, angiosarcoma, alveolar soft part sarcoma, malignant perivascular epithelioid cell tumors (PEComas), osteosarcoma, chondrosarcoma, liposarcomatous tumors, malignant extrarenal rhabdoid tumors, Ewing sarcoma/primitive neuroectodermal tumor, and other rare histotypes. Embryonal rhabdomyosarcoma (20%), Ewing sarcoma/primitive neuroectodermal tumor (17%), angiosarcoma (14%), and pleomorphic rhabdomyosarcoma (13%) appeared to be more common than the others, although there was no single overwhelmingly prevalent histotype in the group. A subset, including embryonal rhabdomyosarcoma, alveolar soft part sarcoma, and PEComas, peak in the premenopausal years, but most of the others were observed in postmenopausal women. Favorable outcomes have been reported for the patients diagnosed with alveolar soft part sarcoma, and the prognosis for their counterparts with PEComa remains a matter of debate. Multimodal therapeutic approaches to contemporary patients with embryonal rhabdomyosarcomas have resulted in significantly improved outcomes. Unfortunately, most of the other sarcomas have been associated with rapid tumor progression and unfavorable patient outcomes. The differential diagnosis for these sarcomas is often extensive and varies by histotype, but their accurate diagnosis fundamentally requires the careful exclusion of biphasic malignancies.

Primitive neuroectodermal tumors in patients with testicular germ cell tumors usually resemble pediatric-type central nervous system embryonal neoplasms and lack chromosome 22 rearrangements

Primitive neuroectodermal tumors (PNETs) are one of the most frequent types of 'non-germ cell' tumor in patients with testicular germ cell tumors and have a guarded prognosis when present in metastatic sites after cisplatin-based chemotherapy. Improved treatments, including targeted therapy, require understanding the biology of these neoplasms. We therefore analyzed the morphologic, immunohistochemical and molecular biologic features of 14 PNETs from 14 patients with concurrent or previous testicular germ cell tumors; 12 tumors were from metastatic sites and 2 were primary in the testis. Using standard light microscopic criteria for central nervous system and peripheral PNETs, we classified nine tumors as medulloepithelioma, three as medulloblastoma/supratentorial PNET, one as neuroblastic tumor with abundant neuropil and true rosettes and one as small cell embryonal tumor/PNET (Ewing sarcoma-like). Immunostains directed against INI1, CD57, S-100 protein, NeuN, WT1, neurofilament, CD99, GFAP, synaptophysin, chromogranin, AE1/AE3 cytokeratin, Fli-1 and collagen IV were performed for each case. INI1 was diffusely and strongly positive in all tumors whereas the other stains, except for cytoplasmic WT1 (which showed substantial reactivity in most tumors), were mostly focal to negative, including CD99 (eight negative, six focal) and Fli-1 (all negative). The most consistently reactive 'neuroendocrine' marker was CD57. Each case was also analyzed for chromosome 22 rearrangements using a FISH-based break-apart probe method. Only 1 tumor, classified as medulloepithelioma, was scored positive for chromosome 22 translocation (22% rearranged cells) and the remaining 13 were negative, including the one case that resembled peripheral PNET. We conclude that PNETs derived from testicular germ cell tumors mostly resemble central nervous system PNETs and generally lack the chromosome 22 translocation of peripheral PNETs. Future treatment strategies should take these findings into account.

Ewing sarcoma-primitive neuroectodermal tumor of the uterus: a clinicopathologic, immunohistochemical and ultrastructural study of one case

INTRODUCTION

Ewing sarcoma-primitive neuroectodermal tumors (ES/PNET) constitute a family of neoplasms characterized by a continuum of neuroectodermal differentiation. ES/PNET of the uterus is rare. There are 43 cases published in the English literature as far as we know. We describe an additional case.

CASE REPORT

A 56-year-old woman presented with a 2-month history of irregular menopausal vaginal bleeding. After surgical excision, microscopic, immunohistochemical and electron microscopic examination suggested the diagnosis of ES/PNET. The patient underwent combined chemotherapy consisting of ifosfamide, etoposide, and cisplatin. She was alive with no evidence of recurrence or metastasis after 41 months of the initial operation.

DISCUSSION

In spite of the rarity of ES/PNET, we should consider it in the differential diagnosis of small cell neoplasms of the uterus.

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.

Primary cutaneous Ewing sarcoma/primitive neuroectodermal tumour: a clinicopathological analysis of seven cases highlighting diagnostic pitfalls and the role of FISH testing in diagnosis

Aims:

To perform a clinicopathological analysis of a series of primary cutaneous Ewing sarcomas/primitive neuroectodermal tumours (ES/PNET) to highlight the pathological features, discuss the differential diagnosis, emphasise the role of molecular testing (particularly fluorescence in situ hybridisation, FISH) in diagnosis and outline the patients’ clinical course.

Methods:

Seven cases of primary cutaneous ES/PNET were identified from the authors’ consultation files.

Results:

The patients were aged 16–61 years (median 25). Five were female and two were male. Five cases involved the limbs and two the trunk. Five were initially misdiagnosed (three as carcinoma and two as melanoma). All cases were characterised histologically by sheet-like growth of small round cells with little cytoplasm and showed strong membranous staining for CD99 and positive but variable staining for FLI-1. Six patients showed an EWS rearrangement (five on FISH analysis and one on RT-PCR). All tumours were completely excised. Three patients received adjuvant chemotherapy, one of whom also received radiotherapy. Follow-up was available in all cases (range 11–57 months; median 41). No recurrences or metastases occurred.

Conclusions:

Although rare, primary cutaneous ES/PNET should be considered in the differential diagnosis of cutaneous “small blue cell tumours”. Immunostaining for FLI-1 and molecular testing for evidence of an EWS rearrangement are useful ancillary investigations to confirm the diagnosis. The prognosis of primary cutaneous ES/PNET appears to be more favourable than extracutaneous ES/PNET.

Continuous Fli-1 expression plays an essential role in the proliferation and survival of F-MuLV-induced erythroleukemia and human erythroleukemia

Erythroleukemia induced by Friend Murine Leukemia Virus (F-MuLV) serves as a powerful tool for the study of multistage carcinogenesis and hematological malignancies in mice. Fli-1, a proto-oncogene and member of the Ets family, is activated through viral integration in F-MuLV-induced erythroleukemia, and is the most critical event in the induction of this disease. Fli-1 aberrant regulation is also observed in human malignancies, including Ewing's sarcoma, which is often linked to expression of the EWS/Fli-1 fusion oncoprotein. Here we examined the effects of Fli-1 inhibition to further elucidate its role in these pathological occurrences. The constitutive suppression of Fli-1, through RNA interference (RNAi), inhibits growth and induces death in F-MuLV-induced erythroleukemia cells. Expression of a dominant negative protein Engrailed (En)/Fli-1 reduces proliferation of EWS/Fli-1-transformed NIH-3T3 cells, and both F-MuLV-induced and human erythroleukemia cells. F-MuLV-induced erythroleukemia cells also display increased apoptosis, associated with reduced expression of bcl-2, a known fli-1 target gene. Introduction of En/Fli-1 into an F-MuLV-infected erythroblastic cell line induces differentiation, as shown by increased alpha-globin expression. These results suggest, for the first time, an essential role for continuous Fli-1 overexpression in the maintenance and survival of the malignant phenotype in murine and human erythroleukemias.

Molecular and phenotypic analysis of poorly differentiated sinonasal neoplasms: an integrated approach for early diagnosis and classification

Primary poorly differentiated (small round and non-small) sinonasal neoplasms comprise histogenetically and biologically diverse entities with overlapping morphologic features. Because of the limited initial biopsy tissue materials, differential diagnostic difficulties may arise and complicate timely management of some cases. We used immunohistochemical and molecular marker analyses in a large cohort of these tumors to optimize their early diagnosis and classification. Fifty-two tumors of the skull base and sinonasal regions and, for comparison, 19 poorly differentiated neoplasms of other head and neck sites were analyzed by a panel of immunohistochemical markers including those of epithelial, mesenchymal, melanocytic, and neuroectodermal origin using tissue microarray. Reverse transcriptase-polymerase chain reaction analysis of messenger RNA for EWS-FLI1 and PAX-FKHR fusion transcripts and the human achaete-scute homolog-1 gene was performed on 24 of the 52 sinonasal tumors and the 19 tumors of other sites for comparison. The immunohistochemical results substantiated the phenotypic assessment and the initial diagnosis in 49 of the 52 tumors. In 4 instances the integrated markers and phenotypic analyses led to reclassification of 3 tumors and confirmed the histogenesis of a mesenchymal tumor with aberrant cytokeratin expression. Molecular analysis of the EWS-FLI1 fusion gene transcript revealed 4 (9.3%) of the 43 tumors to be positive; all were Ewing sarcomas. The human achaete-scute homolog-1 gene transcript was identified in 10 (23.8%) of 42 tumors: 3 of 6 neuroblastomas, all 4 neuroendocrine carcinomas, and 1 each in sinonasal undifferentiated carcinoma, rhabdomyosarcoma, and melanoma. The PAX-FKHR fusion transcript was not detected in any tumors. We conclude that (1) an integrated morphologic and biomarker algorithm may better optimize the early diagnosis of poorly differentiated sinonasal and skull-base tumors; (2) molecular analysis may assist in future biological stratification of certain classes of these tumors; and (3) the human achaete-scute homolog-1 gene transcript is a nonspecific marker for the diagnosis of neuroblastoma.

Analysis of CHOP rearrangement in pleomorphic liposarcomas using fluorescence in situ hybridization

Pleomorphic liposarcoma (PLS) is an aggressive subtype of liposarcoma composed of high-grade sarcoma with pleomorphic lipoblasts. PLS usually exhibits a heterogeneous histology and sometimes has a myxoid or round cell area similar to myxoid/round cell liposarcomas (MLS/RCs). Using fluorescence in situ hybridization (FISH) analysis, we investigated the existence of CHOP split signals in various histological areas of PLS including the MLS/RC-like feature and also estimated the distribution of various signals with polyploidy and amplification. Moreover, to detect CHOP fusion transcripts we performed nested reverse transcription-polymerase chain reaction (RT-PCR). Seven PLSs and three MLS/RCs were selected for FISH analysis using the locus-specific indicator CHOP (12q13) dual color, break apart probe (Vysis, USA). The FISH analysis was applied to formalin-fixed, paraffin-embedded tissue sections of representative areas in all cases. Six of seven PLS cases showed the CHOP split signal ranging from 0.5% to 3% of counted nuclei, while all cases of MLS/RC exhibited CHOP rearrangement in more than 50% of counted nuclei. All cases of PLS showed a varied distribution of extra signals with polyploidy and amplification in each histological area. No CHOP fusion transcript was found in any case of PLS by nested RT-PCR. A CHOP rearrangement in PLS should be recognized only as a representative part of complex karyotypes, because the number of cells with split signals was minute compared with that of MLS/RC, and the signals were found in any area despite their histological differences. The cytogenetic background of PLS and that of MLS/RC are obviously different despite histological similarity.