Immunohistochemical detection of EWS and FLI-1 proteinss in Ewing sarcoma and primitive neuroectodermal tumors: comparative analysis with CD99 (MIC-2) expression

Ultrastructural differences between synovial sarcoma and solitary fibrous tumor: comparative study in adult patients from the National Cancer Institute of Mexico

Synovial sarcoma (SS) and solitary fibrous tumor (SFT) are entities with considerable morphological and immunohistochemical similarities that sometimes show a non-confirmatory profile (TLE1 negative, CD34 and focal or negative STAT6 and lack of specific fusion IHC markers), in which the utility ultrastructure is unknown. A cross-sectional, retrospective, analytical, nonexperimental study was carried out by the Department of Pathology of the National Cancer Institute of Mexico (INCan) e from January 1, 2009 to December 31, 2018. With 17 SFT cases with diffuse or focal CD34 and STAT6 positivity and 18 cases of SS with positive FISH molecular test t(X:18) breakapart were studied by electron microscopy of fresh glutaraldehyde fixed or paraffin-embedded tissue. The ultrastructural findings with a significant difference present in the SS were tandem tight junctions, desmosomes and abundance of dilated rough endoplasmic reticulum (RER) cisternae (p < 0.001, 0.003, and 0.001, respectively); while in the (SFT) the presence of abundant glycogen, basal lamina, long and slender cytoplasmic processes, pinocytic vesicles, hemidesmosomes, and/or dense plaques, collagen skein, and microvilli-like buds (p = 0.028, 0.005, and <0.001 for the last five). We then infer that the five distinctive markers of the SFT are the collagen skeins intermingled with cellular processes in a shape of "squid can," and the pinocytic vesicles as they were not observed in any case of SS. Conversely, tandem junctions were not found in any SFT case. Although the presence of multivesicular buds in the SFT was not significant, it had not been previously described.

FLI-1 is expressed in a wide variety of hematolymphoid neoplasms: a special concern in the differential diagnosis

Friend Leukemia Virus Integration 1 (FLI-1) is a member of E26 transformation-specific family of transcription factors that participates in hematopoietic and vascular endothelial cell development. Immunohistochemical detection of FLI-1 has been widely used to diagnose vascular tumors or, more evidently, Ewing's sarcoma. However, the expression pattern of FLI-1 in hematolymphoid neoplasms remains unclear. Therefore, in this study, we aimed to investigate the expression of FLI-1 in these tumors, focusing on high-grade lesions, which presents a diagnostic challenge by mimicking Ewing's sarcoma. We evaluated the expression FLI-1 in various types of lymphoid and plasmacytic tumors, including 27 plasmablastic lymphomas, 229 diffuse large B-cell lymphomas, 22 precursor T- or B-lymphoblastic lymphomas, 24 angioimmunoblastic-type nodal T-follicular helper cell lymphomas, 52 peripheral T-cell lymphomas, NOS, 18 Burkitt lymphomas, 18 non-gastric lymphomas of mucosa-associated lymphoid tissue, 38 chronic lymphocytic leukemia/small lymphocytic lymphomas, 15 mantle cell lymphomas, 23 gastric MALT lymphomas, 50 plasma cell myelomas, and 38 follicular lymphomas. We calculated the H-scores of FLI-1 immunostaining, ranging from 0 to 200, and used the scores to analyze the clinicopathological significance of FLI-1 statistically. FLI-1 was expressed to varying degrees in all types of hematological tumors. FLI-1 expression was detected in 84.1% of patients (466/554). FLI-1 was highly expressed in precursor T- or B-lymphoblastic lymphomas. Follicular lymphomas exhibited low FLI-1 expression. In plasmablastic lymphoma, 85.2% of the patients were focally positive for FLI-1. FLI-1 expression did not correlate with clinicopathological variables, such as demographic data or disease stage, in patients with plasmablastic lymphoma and diffuse large B-cell lymphoma. However, FLI-1 overexpression was associated with poorer overall survival in patients with plasmablastic lymphoma. This study demonstrates that FLI-1 is expressed in various hematolymphoid neoplasms. FLI-1 expression can lead to diagnostic confusion, especially in small blue round cell tumors, such as lymphoblastic lymphoma, plasmablastic lymphoma, and plasma cell myeloma, when distinguishing tumors positive for CD99 and CD56 without CD3, CD20, or CD45. Our findings also suggested the possibility of FLI-1 as a potential prognostic biomarker for plasmablastic lymphoma.

Fine-Needle Aspiration Diagnosis of Lymphoma Based on Cytomorphology Alone: How Accurate is it? - A Cyto-Histopathology Correlative Study

Context:

Fine-needle aspiration cytology (FNAC) is a rapid and accurate first-line diagnostic modality in lymphadenopathy.

Aims:

To determine the utility of FNAC for the diagnosis of lymphoma and highlight the various pitfalls in morphological interpretation.

Settings and Design:

This was a retrospective study of 3 years duration in which cytology diagnosis was compared with the follow-up histopathology diagnosis wherever available.

Results:

A cytodiagnosis of lymphoma was made in a total of 868 cases (2.8%) out of nearly 33,000 FNAC performed during the study period; 556 (64.1%) cases were diagnosed as non-Hodgkin lymphoma (NHL), 198 (22.8%) as Hodgkin lymphoma (HL), and in 114 (13.1%) cases, a cytological diagnosis of lymphoma without further categorization was given. Histopathological reports were available in 348 cases, with an overall concordance rate of 93.1% (324), which was slightly higher in the HL cases (95.8%) as compared to NHL (91.7%). Twenty-four cases (6.9%) showed discordant cytological diagnosis with subsequent histopathology. The main reasons for the erroneous diagnosis were the over-interpretation of the germinal center cells as atypical lymphoid cells, over-interpretation of immunoblasts with prominent nucleoli as Hodgkin cells, and sheets of monomorphic lymphoid cells interpreted as low-grade lymphoma.

Conclusion:

Cytomorphology alone can make a correct basic diagnosis of lymphoma with a high degree of accuracy. The errors in interpretation can be further reduced by careful attention to the diagnostic pitfalls and common differential diagnoses.

Primary renal Ewing's sarcoma in a young male treated completely by surgical excision without chemotherapeutic agents: Case report

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Primary renal Ewing sarcoma is a rare tumor in adults.

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Proper surgical resection is the most important treatment step.

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Further studies needed to establish treatment for this tumor.

Introduction

Primary renal Ewing’s sarcoma is a rare tumor with dismal prognosis. The main treatment modality of treatment is surgical excision with adjuvant or neoadjuvant chemotherapy.

Case presentation

We present a case of primary renal EWS in 27-year-old male. He presented to our center complaining of three days history of severe left flank pain associated with nausea and vomiting. Computerized tomography (CT) revealed a 10 × 7 × 6.5 cm left lower pole renal mass. Left radical nephrectomy was performed and revealed a tumor with uniform round to oval nuclei cells. The cells stained strongly positive for CD 99. The diagnosis was established as primary renal Ewing’s sarcoma. The patient refused the chemotherapy. Fortunately, he was free of the disease on regular clinical and radiological follow-up, the last follow up was 30 months post-nephrectomy.

Conclusion

This case highlights the importance of proper surgical treatment and its role in the managing this type of malignancy especially in localized disease at presentation.

Retroperitoneal extraosseous peripheral primitive neuroectodermal tumor in a Formosan serow: case report and literature review

A 10-y-old female captive Formosan serow (Capricornis swinhoei) was inactive and was azotemic. An autopsy was performed following her death, and multiple irregularly shaped, white-to-gray masses of 0.5-2 cm diameter were noted on both ureters, the left adrenal gland, urinary bladder, and uterus. Microscopically, organs were effaced by a poorly demarcated, highly infiltrative neoplasm, composed of neoplastic round cells arranged in islands, sheets, or nests with occasional rosette formation. The neoplastic cells were small: ≤2 red blood cell (≤ 15 μm) diameter. The neoplastic cells were positive for CD56, CK, FLI-1, and NSE, but negative for desmin, GFAP, melan A, NF, PAX-8, S100, synaptophysin, and vimentin. Therefore, the diagnosis of retroperitoneal extraosseous peripheral primitive neuroectodermal tumor (pPNET) was made. pPNET with FLI-1 expression has not been reported previously in animals, to our knowledge.

OLIG2 is a marker of the fusion protein-driven neurodevelopmental transcriptional signature in alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma (RMS) is associated with an underlying pathogenic translocation involving either PAX3 or PAX7 and FOXO1. The presence or absence of this fusion defines the biology and clinical behavior of this subtype of RMS and its identification in tumors is relevant to prognostication and treatment planning. To further explore the unique characteristics of fusion-driven RMS, we leveraged a published gene expression data set to perform an unbiased comparison of 33 fusion-positive and 25 fusion-negative RMS cases. Our analyses revealed 1790 expressed loci with more than two-fold differential expression at a threshold of P < .05. Genes with increased expression in fusion-positive relative to fusion-negative RMS were significantly enriched for those involved in "nervous system development," "neuron differentiation," and "neurogenesis," highlighting a neurodevelopmental gene expression signature driven by the alveolar RMS-associated fusion protein. We show that neurodevelopmental genes are enriched near PAX3-FOXO1 fusion protein binding sites, suggesting a genome-wide fusion protein-mediated activation of cis regulatory elements. Among the genes with differential expression in fusion-positive versus fusion-negative RMS, we identified expression of the transcriptional regulator of motor neuron and oligodendrocyte development, OLIG2, as a marker of the fusion protein-dependent neurodevelopmental signature. Immunohistochemical analysis of a cohort of 73 RMS specimens revealed OLIG2 expression in 96.4% of fusion-positive RMS (N = 27/28), but only in 6.7% of fusion-negative RMS (N = 3/45; P < .001). The proportion of OLIG2-expressing cells in fusion-negative cases did not exceed 5%, while 92.9% of fusion-positive cases showed expression in at least 5% of cells. Our findings identify OLIG2 expression as a unique manifestation of a neurodevelopmental gene expression signature driven by the oncogenic fusion protein characteristic of alveolar RMS, which may aid in the diagnostic and prognostic distinction of fusion-positive cases.

A Rare Case of Dumbbell-shaped Primary Intraspinal Peripheral Primitive Neuroectodermal Tumor Involving Thoracic Spinal Epidural Space

Primary intraspinal primitive neuroectodermal tumor (PNET) is a type of round cell malignant tumor which is reported only above 100 in literature. We report a case of epidural thoracic peripheral PNET, discuss its pathological features, radiology, and treatment options.

EWSR1 fusion proteins mediate PAX7 expression in Ewing sarcoma

PAX7 is a paired-box transcription factor that is required for the developmental specification of adult skeletal muscle progenitors in mice. We previously demonstrated PAX7 expression as a marker of skeletal muscle differentiation in rhabdomyosarcoma. Here, using analyses of published whole-genome gene expression microarray data, we identify PAX7 as a gene with significantly increased expression in Ewing sarcoma in comparison to CIC-DUX4 round cell sarcoma. Analysis of PAX7 in a large cohort of 103 Ewing sarcoma cases by immunohistochemistry revealed expression in 99.0% of cases (102/103). PAX7 expression was noted in cases demonstrating three distinct Ewing sarcoma EWSR1 translocations involving FLI1, ERG, and NFATc2. No PAX7 expression was observed in any of 27 cases of CIC-DUX4 sarcoma by immunohistochemistry (0%; 0/27). Exploring the mechanism of PAX7 expression in Ewing sarcoma using curated RNA- and ChIP-sequencing data, we demonstrate that the EWSR1 fusion protein is required for PAX7 expression in Ewing sarcoma and identify a candidate EWSR1-FLI1-bound PAX7 enhancer that coincides with both a consensus GGAA repeat-containing binding site and a peak of regulatory H3K27 acetylation. Taken together, our findings provide mechanistic support for the utility of PAX7 immunohistochemistry in the diagnosis of Ewing sarcoma, while linking this sarcoma of uncertain histogenesis to a key transcriptional regulator of mammalian muscle progenitor cells.

Aberrant expression of FLI-1 in melanoma

Friend leukemia integration site 1 (FLI-1) nuclear transcription factor has been proposed as a suitable tool in the differential diagnosis of small round cell sarcomas. It has also been described as a nuclear marker of endothelial differentiation. Expression of FLI-1 has been demonstrated in Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) and vascular neoplasms. In the present study, we describe 2 cases of metastatic melanoma with small round blue cell morphology that showed strong nuclear expression of FLI-1. Because of the small round blue cell morphology and negative immunohistochemical staining for pan-melanocytic cocktail (HMB45, anti MART1 and anti-tyrosinase) and SOX10 in both cases, FLI-1 immunostaining was requested as part of the tumors workup. Ultimately, both cases were established as being metastatic melanoma. Dermatopathologists should be aware that melanoma can be strongly positive for FLI-1 and not misinterpret these cases for ES/PNET or vascular lesions, especially when melanomas show unusual morphology.

Ewing Sarcoma/Primitive Neuroectodermal Tumor of the Kidney: A Rare and Lethal Entity

Ewing sarcoma/primitive neuroectodermal tumor represents a spectrum of undifferentiated tumors with similar biology that together represent the second most common sarcoma in the pediatric-young adult age range. Very rarely, this tumor presents as a primary neoplasm of the kidney. The clinical presentation of this tumor is not specific, and other renal tumors may present with a similar histologic appearance. Establishing the correct diagnosis is critical because renal Ewing sarcoma/primitive neuroectodermal tumor carries a strikingly dismal prognosis and thus dictates a specific treatment strategy. A low threshold for the use of ancillary molecular tests is recommended, particularly in diagnostically problematic cases. Important considerations with regards to morphology, immunohistochemistry, and molecular alterations will be reviewed here and should be taken into account before rendering this rare and lethal diagnosis.

Ewing sarcoma: a chronicle of molecular pathogenesis

Sarcomas have traditionally been classified according to their chromosomal alterations regardless of whether they accompany simple or complex genetic changes. Ewing sarcoma, a classic small round cell bone tumor, is a well-known mesenchymal malignancy that results from simple sarcoma-specific genetic alterations. The genetic alterations are translocations between genes of the TET/FET family (TLS/FUS, EWSR1, and TAF15) and genes of the E26 transformation-specific (ETS) family. In this review, we intend to summarize a chronicle of molecular findings of Ewing sarcoma including recent advances and explain resultant molecular pathogenesis.

Comparison of Primary Spinal Central and Peripheral Primitive Neuroectodermal Tumors in Clinical and Imaging Characteristics and Long-Term Outcome

OBJECTIVE

Primary spinal primitive neuroectodermal tumors are extremely rare entities. The purpose of this study was to analyze the differences in clinical and imaging characteristics and outcomes between primary spinal central PNETs (cPNETs) and peripheral PNETs (pPNETs).

METHODS

There were 25 consecutive patients with primary spinal primitive neuroectodermal tumors enrolled. The diagnosis was cPNET in 6 patients with negative CD99 expression and pPNET in 19 patients with positive CD99 expression. Gross total resection (GTR) was achieved in 12 patients, subtotal resection was performed in 9 patients, and partial resection was performed in 4 patients. Postoperative chemotherapy was given to 14 patients, and radiotherapy was given to 16 patients.

RESULTS

The age at diagnosis was significantly younger in the cPNET group (mean 12.8 years) compared with the pPNET group (mean 22.5 years) (P = 0.040); the 2 pathologies did not show a significant difference in prognosis. GTR (P = 0.041), radiotherapy (P = 0.008), and GTR with radiotherapy (P = 0.009) were significant factors leading to a higher 2-year survival rate. Kaplan-Meier analysis showed that radiotherapy (P < 0.001) and GTR with radiotherapy (P = 0.040) resulted in a longer median survival time. Patients who underwent GTR, chemotherapy, and radiotherapy all together had the highest 1-year (100.0%) and 2-year (71.4%) survival rates and the longest median survival time (32 months).

CONCLUSIONS

Patients with spinal cPNETs were younger compared with patients with pPNETs. The prognosis of spinal cPNETs and pPNETs was poor with no significant difference between the entities. The most beneficial treatment modality is GTR combined with adjuvant radiotherapy and chemotherapy.

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.

Cyclin D1 is a useful marker for soft tissue Ewing's sarcoma/peripheral Primitive Neuroectodermal Tumor in children and adolescents: A comparative immunohistochemical study with rhabdomyosarcoma

Cyclin D1 amplification and/or overexpression contribute to the loss of the regulatory circuits that govern G1-S transition phase of the cell cycle, playing pivotal roles in different human malignant tumors, including breast, colon, prostate cancer, lymphoma, melanoma and neuroblastoma. In vitro studies have shown that cyclin D1 is overexpressed in Ewing's sarcoma (EWS)/peripheral Primitive Neuroectodermal Tumor (pPNET), but not in rhabdomyosarcoma cell lines. Only a few immunohistochemical studies are available on cyclin D1 expression in EWS/pPNET, which confirmed its expression only in a limited number of cases. The aim of the present study was a comparative immunohistochemical analysis of the expression and distribution of cyclin D1 in a large series of pediatric/adolescent soft tissue EWS/pPNETs and rhabdomyosarcomas (both embryonal and alveolar subtypes) to assess its potential usefulness in their differential diagnosis. Notably cyclin D1 was strongly and diffusely expressed in all cases (20/20) of EWS/pPNET, while it was lacked in all cases (15/15) of rhabdomyosarcomas. Immunohistochemical overexpression of cyclin D1 in EWS/pPNET is a novel finding which could be exploitable as a diagnostic immunomarker for this tumor. Although highly sensitive, cyclin D1 is not specific for EWS/pPNET, and thus it should not be evaluated alone but in the context of a wide immunohistochemical panel. Accordingly, we first emphasize that when pathologists are dealing with a small round blue cell tumor of soft tissues in pediatric/adolescent patients, a strong and diffuse nuclear expression of cyclin D1 is of complementary diagnostic value to CD99 and FLI-1 in confirming diagnosis of EWS/pPNET and in ruling out rhabdomyosarcoma.

A Primary Primitive Neuroectodermal Tumor Arising from Left Subclavian Vein and Extending along Left Brachiocephalic Vein and Superior Vena Cava into Right Atrium

Primitive neuroectodermal tumor (PNET) is an extremely rare malignancy thought to be derived from fetal neuroectodermal precursor cells. It usually occurs in central and peripheral nervous system or soft tissue and bone, while intravenous or intracavitary PNET is considered as an extremely rare tumor. We reported a case of a 44-year-old woman who presented with the left unilateral facial and neck swelling. Magnetic resonance imaging revealed a tape-shaped solid mass within left subclavian vein, left brachiocephalic vein, superior vena cava, and right atrium; the proximal end proportion occupied almost the entire right atrium with a pedicle flip protruded into the right ventricle. Ultrasonography revealed an irregular hypoechnoic mass arising from the left subclavian vein, which extended along the left brachiocephalic vein and superior vena cava into the right atrium and up to the right ventricle. Positron emission tomography-computed tomography revealed several hypermetabolic thyroid nodules with no evidence of intravenous hyperactive lesion. The patient underwent tumor resection under cardiopulmonary bypass. At 15 days postoperatively, total thyroidectomy and resection of the left subclavian vein were simultaneously performed. The patient received chemotherapy and radiotherapy later. Histologically, the neoplasm displayed small, round, blue cells with hyperchromatic nuclei and scant cytoplasm. The neoplastic cells showed a strong immunopositivity for CD99, synaptophysin, CD56, CD57, and friend leukemia integration 1, thus confirming a diagnosis of the PNET. Histopathological examination of the thyroid showed papillary carcinoma. Thus, this PNET had no definitive organ or tissue of origin, which primarily originated from the left subclavian vein with tumor extension along the superior vena cava to the right ventricle.

Targeted imaging of Ewing sarcoma in preclinical models using a 64Cu-labeled anti-CD99 antibody

PURPOSE

Ewing sarcoma is a tumor of the bone and soft tissue characterized by diffuse cell membrane expression of CD99 (MIC2). Single-site, surgically resectable disease is associated with an excellent 5-year event-free survival; conversely, patients with distant metastases have a poor prognosis. Noninvasive imaging is the standard approach to identifying sites of metastatic disease. We sought to develop a CD99-targeted imaging agent for staging Ewing sarcoma and other CD99-expressing tumors.

EXPERIMENTAL DESIGN

We identified a CD99 antibody with highly specific binding in vitro and labeled this antibody with (64)Cu. Mice with either subcutaneous Ewing sarcoma xenograft tumors or micrometastases were imaged with the (64)Cu-labeled anti-CD99 antibody and these results were compared with conventional MRI and 2[18F]fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) imaging.

RESULTS

(64)Cu-labeled anti-CD99 antibody demonstrated high avidity for the CD99-positive subcutaneous tumors, with a high tumor-to-background ratio, greater than that demonstrated with FDG-PET. Micrometastases, measuring 1 to 2 mm on MRI, were not detected with FDG-PET but were readily visualized with the (64)Cu-labeled anti-CD99 antibody. Probe biodistribution studies demonstrated high specificity of the probe for CD99-positive tumors.

CONCLUSIONS

(64)Cu-labeled anti-CD99 antibody can detect subcutaneous Ewing sarcoma tumors and metastatic sites with high sensitivity, outperforming FDG-PET in preclinical studies. This targeted radiotracer may have important implications for the diagnosis, surveillance, and treatment of Ewing sarcoma. Similarly, it may impact the management of other CD99 positive tumors.

Intracranial metastasis from primary spinal primitive neuroectodermal tumor

Primary spinal primitive neuroectodermal tumors (PNET) are rare tumors, with only 94 cases reported till date. Metastasis to brain from a spinal PNET is even rarer. In the present report, we evaluate the pathology and treatment of solitary intracranial metastasis from spinal PNET in a 22-year-old female who presented with headache and left hemiparesis and was diagnosed to have right parietal parasagittal tumor. She has been previously diagnosed to have cervicothoracic primary spinal PNET, and was treated by surgery, radiotherapy, and chemotherapy seven years back. The intracranial tumor has been removed and pathological examination confirmed as PNET. She received radiotherapy and chemotherapy with ifosfamide and etoposide, following surgery for the right parietal PNET. At 20 months follow-up, patient is stable and has no recurrence of the disease. Critical review of reported cases of primary spinal PNET metastsising to brain was done.

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.

Renal primitive neuroectodermal tumors

Primitive neuroectodermal tumors exist as a part of the Ewing sarcoma/primitive neuroectodermal tumor family. These tumors most commonly arise in the chest wall and paraspinal regions; cases with a renal origin are rare entities, but have become increasingly reported in recent years. Although such cases occur across a wide age distribution, the average age for a patient with a renal primitive neuroectodermal tumor is the mid- to late 20s, with both males and females susceptible. Histologically, these tumors are characterized by pseudorosettes. Immunohistochemically, CD99 is an important diagnostic marker. Clinically, these are aggressive tumors, with an average 5-year disease-free survival rate of only 45% to 55%. Given that renal primitive neuroectodermal tumor bears many similarities to other renal tumors, it is important to review the histologic features, immunostaining profile, and genetic abnormalities that can be used for its correct diagnosis.

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.

Primary spinal extradural Ewing's sarcoma (primitive neuroectodermal tumor): Report of a case and meta-analysis of the reported cases in the literature

Background:

Primary spinal primitive neuroectodermal tumors (PNET) and/or spinal extraskeletal Ewing's sarcoma family tumors (ESET) are rare lesions appearing in the spinal extradural space. One hundred forty-one primary spinal PNETs, including 29 intramedullary lesions, have been reported in the literature. Encountering a case of primary epidural EES/peripheral PNET (pPNET) in sacral level, which is the fifth one occurring at this level in the literature, we have tried to conduct a meta-analysis of the reported cases.

Case Description:

A 44-year-old lady with epidural EES/pPNET is reported here. She was once operated for L5/S1 herniated disc, which did not ameliorate her symptoms. The clinical, imaging, surgical, and histopathologic characteristics of our case are presented and wide search of the literature is also done. All the reports were level 3 or less evidences and most of the series had missing parts. 106 cases of primary intraspinal (extradural/extramedullary-intradural) EES/pPNET and 29 cases of primary intramedullary PNET (CNS-PNET) have been reported in the literature. The most common clinical presentation in both entities was muscle weakness proportionate to the tumor location. Distant metastasis occurred in 38 of 99 (38%) cases of primary intraspinal EES/pPNET, while the rate of metastasis was 48% in patients with PNETs occurring in the intramedullary region (P > 0.05). One-year survival rate of the patients who underwent chemo-radiation after total or subtotal resection was better than those who did not receive chemotherapy or radiotherapy, or did not have total or subtotal resection. However, this difference was not repeated in 2-year survival rate in any of the tumor groups.

Conclusion:

It seems that total or subtotal removal of the tumor and adjuvant chemo- and radiation therapy can improve the outcome in these patients.

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.

Malignant small round cell tumors

Malignant small round cell tumors are characterised by small, round, relatively undifferentiated cells. They generally include Ewing's sarcoma, peripheral neuroectodermal tumor, rhabdomyosarcoma, synovial sarcoma, non-Hodgkin's lymphoma, retinoblastoma, neuroblastoma, hepatoblastoma, and nephroblastoma or Wilms’ tumor. Other differential diagnoses of small round cell tumors include small cell osteogenic sarcoma, undifferentiated hepatoblastoma, granulocytic sarcoma, and intraabdominal desmoplastic small round cell tumor. Differential diagnosis of small round cell tumors is particularly difficult due to their undifferentiated or primitive character. Tumors that show good differentiation are generally easy to diagnose, but when a tumor is poorly differentiated, identification of the diagnostic, morphological features is difficult and therefore, no definitive diagnosis may be possible. As seen in several study reports, fine needle aspiration cytology (FNAC) has become an important modality of diagnosis for these tumors. The technique yields adequate numbers of dissociated, viable cells, making it ideally suitable for ancillary techniques. Typically, a multimodal approach is employed and the principal ancillary techniques that have been found to be useful in classification are immunohistochemistry and immunophenotyping by flow cytometry, reverse transcriptase polymerase chain reaction (RT-PCR), fluorescence in situ hybridization (FISH), and electron microscopy. However, the recent characterization of chromosomal breakpoints and the corresponding genes involved in malignant small round cell tumors means that it is possible to use molecular genetic approaches for detection.

Intraspinal primitive neuroectodermal tumor in a man with neurofibromatosis type 1: Case report and review of the literature

BACKGROUND

The occurrence of primitive neuroectodermal tumors (PNET) in patients with neurofibromatosis type 1 (NF1) has only been reported in two other cases in English-Language literature. Owing to the rarity of intraspinal PNET and the extremely high gene mutation variability in NF1, there is currently no conclusive evidence to suggest that PNET is associated with NF1. Here, we report a case of intradural PNET in a patient with NF1.

CASE DESCRIPTION

A 27-year-old male underwent a C1-C3 laminectomy for resection of an intramedullary mass. Histopathology and immunohistopathology analysis was performed. Microscopic examination and immunohistochemical staining indicated the mass was a primitive neuroectodermal tumor. Within 1 month after tumor resection, the patient developed leptomeningeal carcinomatosis. The patient was not a candidate for radiation therapy but underwent palliative systemic chemotherapy. He subsequently developed neutropenia and died 3 months after tumor resection.

CONCLUSION

To our knowledge, this is the first reported intraspinal PNET associated with NF1. Genetic analysis of CNS PNETs suggests a possible correlation, but larger case series are needed to support this theory.

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.

Pathobiologic markers of the ewing sarcoma family of tumors: state of the art and prediction of behaviour

Over the past three decades, the outcome of Ewing sarcoma family tumor (ESFT) patients who are nonmetastatic at presentation has improved considerably. The prognosis of patients with metastatic disease at the time of diagnosis and recurrence after therapy remains dismal. Drug-resistant disease at diagnosis or at relapse remains a major cause of mortality among patients diagnosed with ESFT. In order to improve the outcome for patients with potential relapse, there is an urgent need to find reliable markers that either predict tumor behaviour at diagnosis or identify therapeutic molecular targets at the time of recurrence. An improved understanding of the cell of origin and the molecular pathways that regulate tumorigenicity in ESFT should aid us in the search for novel therapies for ESFT. The purpose of this paper is thus to outline current concepts of sarcomagenesis in ESFT and to discuss ESFT patterns of differentiation and molecular markers that might affect prognosis or direct future therapeutic development.

RNAi phenotype profiling of kinases identifies potential therapeutic targets in Ewing's sarcoma

Background

Ewing's sarcomas are aggressive musculoskeletal tumors occurring most frequently in the long and flat bones as a solitary lesion mostly during the teen-age years of life. With current treatments, significant number of patients relapse and survival is poor for those with metastatic disease. As part of novel target discovery in Ewing's sarcoma, we applied RNAi mediated phenotypic profiling to identify kinase targets involved in growth and survival of Ewing's sarcoma cells.

Results

Four Ewing's sarcoma cell lines TC-32, TC-71, SK-ES-1 and RD-ES were tested in high throughput-RNAi screens using a siRNA library targeting 572 kinases. Knockdown of 25 siRNAs reduced the growth of all four Ewing's sarcoma cell lines in replicate screens. Of these, 16 siRNA were specific and reduced proliferation of Ewing's sarcoma cells as compared to normal fibroblasts. Secondary validation and preliminary mechanistic studies highlighted the kinases STK10 and TNK2 as having important roles in growth and survival of Ewing's sarcoma cells. Furthermore, knockdown of STK10 and TNK2 by siRNA showed increased apoptosis.

Conclusion

In summary, RNAi-based phenotypic profiling proved to be a powerful gene target discovery strategy, leading to successful identification and validation of STK10 and TNK2 as two novel potential therapeutic targets for Ewing's sarcoma.

Pre-B-cell acute lymphoblastic leukemia with bulk extramedullary disease and chromosome 22 (EWSR1) rearrangement masquerading as Ewing sarcoma

We report a 2-year-old female with a subcutaneous tumor who was initially misdiagnosed as suffering from Ewing sarcoma with a positive EWSR1 rearrangement and EWS/FLI1 transcript. After finding lymphoblasts in peripheral blood, the diagnosis of acute lymphoblastic leukemia was established. This necessitated further analysis of the subcutaneous tumor. The tissue was positive for immature B-cell markers and an immunoglobulin heavy chain gene rearrangement, which confirmed the final diagnosis of common type acute lymphoblastic leukemia with bulk extramedullary disease. The patient was treated with chemotherapy and was in remission 30 months after the diagnosis.

Primary vaginal Ewing's sarcoma or primitive neuroectodermal tumor in a 17-year-old woman: a case report

Introduction

Primary Ewing's sarcoma or primitive neuroectodermal tumor of the genital tract of women is uncommon. Rarer still is its occurrence in the vagina, with only five cases described so far. Out of these, only one case was confirmed using molecular analysis.

Case presentation

We present an extremely rare case of Ewing's sarcoma or primitive neuroectodermal tumor in a 17-year-old Indian girl. She presented with a vaginal mass that was initially diagnosed as a malignant round cell tumor. Immunohistochemistry showed diffuse positivity for vimentin, membranous positivity for MIC2, and positivity for BCL2 and FLI-1. On the other hand, she was negative for cytokeratin, epithelial membrane antigen, desmin, Myo D-1, myogenin and smooth muscle actin. A diagnosis of primitive neuroectodermal tumor was thus offered. Furthermore, a molecular analysis of our patient using reverse transcription-polymerase chain reaction technique showed positivity for t(11; 22) (q24; q12) (EWSR1-FLI1), thus confirming the diagnosis of a Ewing's sarcoma/primitive neuroectodermal tumor. Our patient was offered chemotherapy on Institutional protocol EFT 2001.

Conclusion

This is a rare case of primary vaginal Ewing's sarcoma or primitive neuroectodermal tumor, which was confirmed with molecular analysis, in the youngest patient known so far. This study reinforces the value of integrating morphological features with membranous MIC2 positivity, along with application of molecular techniques in objective identification of an Ewing's sarcoma or primitive neuroectodermal tumor at uncommon sites.

Peripheral neuroectodermal tumor of the vulva: a case report

BACKGROUND

Peripheral neuroectodermal tumors arising from vulva are extremely rare; only 12 cases have been reported so far. These tumors belong to the Ewing sarcoma family of tumors. They occur in bones and variety of soft tissues of chest wall, pelvis, paravertebral region, and lower extremities. Being aggressive tumors, they have poor prognosis.

CASE

We report a case of a 20-year-old woman who presented with a 20 x 15 x 10-cm pedunculated mass arising from the right labium majus. Judicious use of a panel of markers led to diagnosis of peripheral neuroectodermal tumor. The patient died of metastatic disease.

CONCLUSIONS

Judicious use of a panel of markers and a molecular test, if necessary, helps in confirming the diagnosis. Surgery followed by chemotherapy with or without radiation is the treatment of choice.

Small cell tumors of bone

Bone tumors are fortunately rare, but small cell tumors of bone are a relatively common subset of these lesions. They comprise of a diverse group of primary and metastatic neoplasms in both children and adults. The most common small cell tumors of bone include Ewing sarcoma/primitive neuroectodermal tumor, small cell osteosarcoma, multiple myeloma, lymphoma, leukemia, neuroblastoma, rhabdomyosarcoma, and Langerhans cell histiocytosis. Although each entity has its distinctive features, the differential diagnosis of this group of tumors is still challenging because they are all "small, blue, and round cell tumors", histologically. The correct diagnosis of small cell tumors of bone depends on an evaluation of clinical, radiologic, pathologic, and genetic features. Patients' age and sex are very important, as are the signs and symptoms at presentation. Radiologically, which bone is involved, the specific portion of the bone (epiphysis, metaphysis, or diaphysis; cortex vs. medulla) involved, and the radiographic manifestations (lytic, blastic, or mixed lytic and blastic) are also often critical parameters for the diagnosis. In recent years, with a better understanding of the molecular and cytogenetic background of several small cell tumors, more accurate diagnoses have been supported by the clinicopathologic criteria and by a panel of immunohistochemical studies. In this review we will provide an overview of the clinical, radiologic, pathologic, and genetic characteristics of these tumors.

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.

Tissue microarrays: applications in study of p16 and p53 alterations in Ewing's cell lines

Background

Tissue microarrays (TMAs) are used to study genomics and proteomics in several tumour tissue samples. Cell lines (CC) are of great importance in the study of the genetic changes in tumours, and some reveal several aspects of tumour oncogenesis. There are few published reports on Ewing's tumours with TMAs including original tumours (OT) and corresponding CC.

Methods

We have performed four TMAs, from 3 OT and the corresponding CC of successive in vivo and in vitro tumour passages. Xenotransplant CC in nude mice from OT (XT/OT) was made. Subsequently multiple XT were performed and in vitro XT cell line (CC/XT) was obtained. In vivo re-inoculation of CC/XT (XT/CC) was planned. TMAs with the successive tumour passages that grew in nude mice (XT/OT and XT/CC) were analyzed by morphologic pattern (Hematoxilin/eosin), immunohistochemical staining (CD99, FLI1, p16, p53, ki-67), fluorescent in situ hybridization-FISH-(EWSR1 break apart, p16 and p53 status) and gene fusion types.

Results

Heterogeneous results of the p16, p53 and ki67 in OT, XT/OT, CC/XT and XT/CC were observed. The three cell lines revealed EWS/FLI1 rearrangements. p16 gene was deleted only in one case. The deletion was detected by FISH and confirmed by PCR assays. A p53 alteration was found in the second case with monosomy and subsequently polysomic status of chromosome 17 during the evolution of CC. The PCR study revealed p53 mutation. The third case showed hypermethylation in the promoter of p16. The growth of the tumour in nude mice was more accelerated when the inoculation was performed from the CC/XT, increasing progressively over the passages. The third case did not reveal tumour growth in nude mice after the re-inoculation of CC/XT.

Conclusion

The study of several cores from original tumours and successive tumour passages in TMAs facilitated the analysis of the genetic alteration and protein expression in Ewing's tumours.

Primary pleural neoplasia: entities other than diffuse malignant mesothelioma

CONTEXT

Overwhelmingly, the most common neoplasm involving the pleura is metastatic carcinoma. In contrast, diffuse malignant mesothelioma occurs relatively rarely; however, it is nonetheless the most common neoplasm primary to the pleura. Metastatic carcinoma and diffuse malignant mesothelioma each have their own prognostic and therapeutic characteristics. Other primary pleural neoplasms occur uncommonly or rarely, with their own prognostic and therapeutic characteristics.

OBJECTIVE

To review primary pleural neoplasms other than diffuse malignant mesothelioma, to better ensure correct diagnosis and optimal assessment of prognosis and treatment.

DATA SOURCES

Literature review and primary material from the authors' institutions.

CONCLUSIONS

A nonexhaustive group of uncommon to rare benign and malignant primary pleural neoplasms--other than diffuse malignant mesothelioma--are presented, of which one must be aware in order to maintain an appropriate index of suspicion to include them in the differential diagnosis of a pleural tumor.

Application of immunohistochemistry to soft tissue neoplasms

CONTEXT

Soft tissue tumors are composed of numerous and complex diagnostic entities. Because of this complexity and the recognition of an intermediate malignancy category including some tumors with a deceptively bland histologic appearance, soft tissue tumors may represent a major diagnostic challenge to the general practicing pathologist.

OBJECTIVE

To correctly diagnose soft tissue tumors with the ancillary use of immunohistochemistry.

DATA SOURCES

Review of the current literature with emphasis on those tumors for which immunohistochemistry has proven to be particularly useful.

CONCLUSIONS

Immunohistochemistry plays an important role in the diagnosis of soft tissue tumors. One of its major utilities is to correctly identify a tumor as being of mesenchymal or nonmesenchymal origin. Once mesenchymal origin has been established, histologic subtyping according to specific cell lineage may be achieved with the use of lineage-specific markers. Tumors of uncertain cell lineage and tumors with primitive small round cell morphology are often characterized by a unique immunohistochemical phenotype. In this group of tumors, immunohistochemistry is most widely applied and is of greatest value. Despite the rapid development of molecular genetic techniques, immunohistochemistry still remains the most important diagnostic tool in the diagnosis of soft tissue tumors aside from recognition of morphologic features and clinical correlation.

Ewing family of tumours involving the vulva and vagina: report of a series of four cases

BACKGROUND

Ewing's sarcoma and peripheral primitive neuroectodermal tumour (pPNET) are now regarded as two morphological ends of a spectrum of neoplasms, characterised by a t(11;22) or other related chromosomal translocation involving the EWS gene on chromosome 22 and referred to as Ewing family of tumours (EFTs). EFTs are extremely rare in the vulva and vagina, a review of the literature revealing only 13 previously reported possible cases, most of which have not had molecular confirmation. In this study, four new cases of EFTs involving the vulva (three cases) or vagina (one case) are reported.

RESULTS

The tumours occurred in women aged 19, 20, 30 and 40 years and ranged in size from 3 to 8 cm. Morphologically, all neoplasms had a lobulated architecture and were composed of solid aggregates of cells. In one case, occasional rosettes were formed. In all the tumours, there was diffuse membranous staining with CD99; nuclear positivity with FLI-1 was present in two cases. Three cases were focally positive with the broad-spectrum cytokeratin AE1/3, all were diffusely positive with vimentin and all were desmin negative. In two cases, a t(11;22) (q24;q12) (EWSR1-FLI-1) chromosomal translocation was demonstrated by reverse transcriptase-PCR (one case) and fluorescence in situ hybridisation (FISH) (one case), and in another case a rearrangement of the EWSR1 gene on chromosome 22 was demonstrated by FISH. In the other case, a variety of molecular studies did not reveal a translocation involving the EWS gene but this tumour, on the balance of probability, is still considered to represent a neoplasm in the EFTs. Follow-up in two cases revealed that one patient developed pulmonary metastasis and died and another is alive without disease at 12 months.

CONCLUSIONS

This report expands the published literature regarding EFTs involving the vulva and vagina and stresses the importance of molecular techniques in firmly establishing the diagnosis, especially when these neoplasms arise at unusual sites.

Small Round Cell Tumors of Bone

Context.—Primary small round cell tumors of the bone are a heterogeneous group of malignant neoplasms presenting predominantly in children and adolescents. They include Ewing sarcoma/peripheral neuroectodermal tumor or Ewing family tumors, lymphoma, mesenchymal chondrosarcoma, and small cell osteosarcoma. Even though they share many morphological similarities, their unique biological and genetic characteristics have provided substantial insights into the pathology of these diverse neoplasms.

Objective.—To provide an overview of the clinical, radiologic, pathologic, and genetic characteristics of these tumors along with a pertinent review of the literature.

Data Sources.—A literature search using PubMed and Ovid MEDLINE was performed, and data were obtained from various articles pertaining to clinicopathologic, biological, and genetic findings in these tumors. Additionally, findings from rare cases have been included from author's subspecialty experience.

Conclusion.—The diagnosis of small round cell tumors can be made accurately by applying clinicopathologic criteria, as well as a panel of immunohistochemical and genetic studies in appropriate cases. Molecular genetic studies may provide further insight into the biology, histogenesis, and prognosis of these tumors.

Askin tumor with metastasis to the scalp: a histochemical, immunohistochemical and ultrastructural study

A 29-year-old woman presented with facial edema, and imaging disclosed a tumor extending from the anterior chest wall to the anterosuperior aspect of the mediastinum. Transbronchial cytology of the primary tumor and biopsy of the metastatic scalp lesion were performed. Histologically, the tumor consisted of closely packed small round cells. The neoplastic cells generally had round nuclei, finely dispersed chromatin, and small to prominent nucleoli. Histochemically, the cytoplasm of the neoplastic cells contained abundant glycogen and stained with Grimelius silver. Immunohistochemically, the neoplastic cell membranes reacted with CD99 (MIC2) and the neoplastic nuclei reacted with Fli-1, but various other markers, including lymphocyte and skeletal muscle markers, were not detected. No neoplastic cells were also reactive for chromogranin A, synaptophysin, and neurofilament. Ultrastructurally, some neoplastic cells had delicate cytoplasmic processes and contained membrane-bound dense core granules in the cytoplasm. Even if results are immunohistochemically negative for neuroendocrine markers, the combination of immunohistochemistry of CD99 (MIC2) and Fil-1 may be useful in diagnosing Askin tumor or its metastatic lesion.

Friend leukaemia integration-1 expression in malignant and benign tumours: a multiple tumour tissue microarray analysis using polyclonal antibody

BACKGROUND

Friend leukaemia integration-1 (FLI-1) antibody is a useful marker for Ewing's sarcoma/primitive neuroectodermal tumour (EWS/PNET) and vascular tumours. However, it is also expressed in subsets of lymphoblastic lymphoma, Merkel cell carcinoma (MCC) and desmoplastic small round cell tumour (DSRCT).

AIM

To determine expression of FLI-1 in various benign and malignant neoplasms, by immunohistochemical analysis on 4323 tumours using multiple tumour microarrays, as well as on whole sections.

RESULTS

FLI-1 was expressed in 46/62 EWS/PNETs, 2/3 olfactory neuroblastomas, 7/102 small cell carcinomas of the lung, 10/34 MCCs, 1/14 rhabdomyosarcoma, 19/132 non-Hodgkin's lymphomas, 2/3 DSRCTs, and in 53/74 benign and malignant vascular tumours. In addition, 27/508 squamous cell carcinomas, 19/837 adenocarcinomas, 10/400 urothelial bladder cancers, 1/40 basal cell carcinomas, 3/29 liposarcomas, 1/40 glioblastoma multiforme and 9/29 medullar carcinomas of the breast expressed FLI-1. The sensitivity and specificity of FLI-1 to distinguish EWS/PNET from all types of malignancies were 74.2% and 96.0%, respectively. Finally, the sensitivity and specificity of FLI-1 to distinguish EWS/PNET from other small round cell tumours (SRCTs) were 74.2% and 91.6%, respectively.

CONCLUSION

This study was the first to show that FLI-1 can be seen in a variety of solid tumours, some of which had never been explored before. This finding should be kept in mind, especially when using FLI-1 as a marker for finding the primary origin of poorly differentiated metastatic tumour. Finally, despite the expression of FLI-1 in numerous malignancies, it is still considered to be highly sensitive and specific in distinguishing EWS/PNET from other tumour types in general and from other SRCTs in particular.

The application of immunohistochemistry in the diagnosis of bone tumors and tumor-like lesions

Immunohistochemistry (IHC) plays an important role in the diagnosis of some bone tumors, especially in the differential diagnosis of primary from metastatic non-osseous tumors and in the categorization of small-round-blue-cell tumors. This article reviews immunomarkers used in bone tumors and their diagnostic significance.

Keratin-positive Ewing's sarcoma: an ultrastructural study of 12 cases

Ewing's sarcoma/primitive neuroectodermal tumor (EWS/PNET) is an aggressive neoplasm of bone and soft tissue. Histologically, it is characterized by the presence of small round blue cells, which usually express MIC-2 and FLI-1 immunohistochemically. The most specific feature for diagnosis, however, is cytogenetic or molecular evidence of a consistent abnormality, the t(11;22)(q24;q12), or variants thereof. The immunohistochemical expression of keratins in a significant proportion of these cases has been highlighted in several recent studies. The ultrastructural features of these keratin-positive tumors have not, however, been characterized in detail. In this study we analyzed the ultrastructural features of 12 well-documented EWS/PNETs that stained strongly for pankeratin by immunohistochemistry. Ultrastructurally, the tumor cells contained a few organelles, which included a small number of mitochondria, poorly developed Golgi complexes, free ribosomes, and inconspicuous rough-endoplasmic reticulum. Rudimentary cell junctions were seen in 2 tumors while prominent junctions were observed in the remaining 10. Five tumors contained intracytoplasmic filaments, and definite tonofibrils were identified in 2. Well-developed basal lamina around tumor cells were also demonstrated in 2 tumors. Follow-up information was available for all cases. Seven patients died of disease, 2 are alive with disease, and 3 have no current evidence of disease. The cohort includes 5 patients with a type-1 translocation, which has been associated with a better prognosis in some studies; 4 of these patients have died of their disease, and 1 is alive with recurrent disease. This study shows that keratin-positive EWS/PNETs have evidence of epithelial differentiation ultrastructurally, and may possibly represent a more aggressive subset of the EWS/PNET group of tumors.