Immunohistochemical detection of FLI-1 protein expression: a study of 132 round cell tumors with emphasis on CD99-positive mimics of Ewing's sarcoma/primitive neuroectodermal tumor

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

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

Gastrointestinal Ewing Sarcoma: A Clinicopathological and Molecular Genetic Analysis of 25 Cases

Occurrence of extraskeletal Ewing sarcoma (ES) in the gastrointestinal (GI) tract is extremely rare. Here, we report 25 cases of ES arising primarily in the GI tract with a focus on the clinicopathological and molecular features, differential diagnosis, and biological behavior. Thirteen patients (52%) were male, and 12 (48%) were female with age ranging from 9 to 59 years (mean: 36.2 years; median: 38 years). Twenty-one tumors (84%) occurred in the small intestine, 3 (12%) in the stomach, and 1 (4%) in the anal canal. At operation, 8/18 (44.4%) patients presented with abdominopelvic disseminated disease. Tumor size measured from 2 to 25 cm (mean: 8.2 cm; median: 6 cm) in maximum size. Microscopically, the tumors were composed of infiltrative small round, ovoid, or short spindle cells arranged mostly in lobular and solid sheet-like patterns with a rich capillary vasculature. Focal formation of Homer Wright-type rosettes and pseudoalveolar architecture was noted each in 2 (8%) cases and 3 (12%) cases. Besides CD99 (25/25; 100%), Fli-1 (15/15, 100%), and NKX2.2 (14/16; 87.5%), the tumor cells also showed variable staining of CD117 (14/17; 82.4%). Of 25 cases, 23 (92%) demonstrated EWSR1 rearrangement by fluorescence in situ hybridization analysis. The 2 cases with negative fluorescence in situ hybridization results were found to harbor EWSR1::ERG and EWSR1::FLI1 fusion by further RNA sequencing, respectively, with a median follow-up of 12 months (range: 1 to 42 months), 5/19 (26.3%) patients developed visceral metastasis and 12/19 (63.2%) patients died of the disease (range:1 to 33 months; median: 9 months). This study showed that GI ES had a predilection for the small intestine, although other sites of the GI tract could also be involved. GI ES had a poor prognosis with a high rate of mortality, particularly in patients with abdominopelvic disseminated disease. In light of appropriate therapeutic strategies and prognostic considerations, it is essential not to misdiagnose GI ES as gastrointestinal stromal tumor owing to the expression of aberrant CD117.

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.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Primitive Neuroectodermal Tumor Presenting With a Large Subcapsular Hematoma in Pregnancy: A Case Report and Current Literature Review

Primitive neuroectodermal tumors (PNET) are rare, small round cell tumors that are difficult to diagnose. It is important to identify PNET early, utilizing immunohistochemistry and genetic markers, as it is often an aggressive cancer. PNET is most commonly described in men between the ages of 20 and 40, with very few case reports highlighting the development in pregnant patients. We present a case of localized renal PNET in a pregnant patient and highlight the diagnostic work-up and treatment as well as the relationship between pregnancy and the potential development of aggressive tumors.

Ewing's Sarcoma of the Orbit: A Case Report and Literature Review

Ewing's sarcoma (ES) is a malignant small round cell neuroectodermal tumour primarily affecting children in the first and second decade of life. Since ES is difficult to control, early diagnosis is crucial, and the treatment requires a multimodality approach constituting chemotherapy, surgery and radiotherapy. Here, we present a case of ES of orbit in a 17-year-old female diagnosed in 2021. This case report focuses on the clinicopathological presentation and management principles of this rare manifestation of the disease that unilaterally infiltrated into the extraconal space of the orbit as well as the I/L frontal sinus. The patient underwent chemotherapy and radiation, and she is on follow-up.

Synovial sarcoma: cytopathology of 51 cases highlighting the application of ancillary molecular testing

INTRODUCTION

Among sarcomas, synovial sarcoma (SS) is defined by its unique SS18 cytogenetic translocation. Fine needle aspiration (FNA) biopsy is in a key position to exploit this uniqueness for diagnostic purposes.

MATERIALS AND METHODS

Our cytopathology files were searched for examples of SS with histopathologic verification. FNA biopsy, imprint smears, and core needle biopsy (CNB) were performed using standard techniques.

RESULTS

Fifty-one cases from 49 patients (male/female ratio, 1:1; age range, 12-79 years; mean age, 40 years) met the inclusion criteria. Of the 51 cases, 44 (86%) were FNAs, 6 were cytology imprints, and 1 was pleural fluid. Eleven aspirates had concurrent CNB. All cases had tissue confirmation. The biopsy sites included extremities (n = 24; 47%), trunk (n = 12; 24%), lung (n = 8; 16%), head or neck (n = 6; 12%), and pleural fluid (n = 1; 2%). The aspirates were from primary (n = 36; 71%), metastatic (n = 12; 24%), and recurrent (n = 3; 5%) neoplasms. The cytologic diagnoses were SS (69%), suspicious for SS (12%), malignancy (10%), spindle cell neoplasm (4%), and malignancy other than SS (6%). In general, smears and imprints contained dense cell aggregates and single cells composed of a monotonous population having fusiform, rounded, or ovoid banal nuclei and scant cytoplasm. Poorly differentiated SS showed both large epithelioid cell and small cell cytomorphology. When performed, SS18 immunohistochemical and genetic testing was positive in all 19 FNA and 3 CNB cases.

CONCLUSIONS

When coupled with appropriate ancillary testing, FNA biopsy allows for a specific, accurate diagnosis of SS in most cases.

Top 10 Histological Mimics of Neuroendocrine Carcinoma You Should Not Miss in the Head and Neck

BACKGROUND

The spectrum of neuroendocrine neoplasia (NEN) of the head and neck region is wide-ranging and diverse, including a variety of diagnoses stretching from benign and low-malignant tumor forms to highly proliferative, poor prognosis neuroendocrine carcinoma (NEC). Moreover, there are several non-neuroendocrine differential diagnoses to keep in mind as well, displaying various degree of morphological and/or immunohistochemical overlap with bona fide neuroendocrine lesions.

METHODS

Review.

RESULTS

While the growth patterns may vary, well-differentiated NEN usually display a stippled "salt and pepper" chromatin, a granular cytoplasm, and unequivocal expression of neuroendocrine markers such as chromogranin A and synaptophysin. However, these features are often less pronounced in NEC, which may cause diagnostic confusion-not the least since several non-NEC head and neck tumors may exhibit morphological similarities and focal neuroendocrine differentiation.

CONCLUSION

As patients with NEC may require specific adjuvant treatment and follow-up, knowledge regarding differential diagnoses and potential pitfalls is therefore clinically relevant. In this review, the top ten morphological and/or immunohistochemical mimics of NEC are detailed in terms of histology, immunohistochemistry, and molecular genetics.

Molecular testing of soft tissue tumors

BACKGROUND

The diagnosis of soft tissue tumors is challenging, especially when the evaluable material procured is limited. As a result, diagnostic ancillary testing is frequently needed. Moreover, there is a trend in soft tissue pathology toward increasing use of molecular results for tumor classification and prognostication. Hence, diagnosing newer tumor entities such as CIC-rearranged sarcoma explicitly requires molecular testing. Molecular testing can be accomplished by in situ hybridization, polymerase chain reaction, as well as next generation sequencing, and more recently such testing can even be accomplished leveraging an immunohistochemical proxy.

CONCLUSION

This review evaluates the role of different molecular tests in characterizing soft tissue tumors belonging to various cytomorphologic categories that have been sampled by small biopsy and cytologic techniques.

Selective Immunoreactivity for WT1 Carboxy-Terminus Distinguishes Desmoplastic Small Round Cell Tumor From its Histologic Mimics

Desmoplastic small round cell tumor (DSRCT) is an aggressive pediatric round cell sarcoma containing a characteristic EWSR1-WT1 gene fusion. In the absence of genetic data, distinguishing DSRCT from other small round cell tumors of childhood can be problematic due to overlapping histologic and immunohistochemical features. We studied the utility of immunohistochemistry with antibodies targeting both the amino-terminal and carboxy-terminal regions of the Wilms tumor-1 (WT1) protein in differentiating these groups of tumors. The study cohort included 33 cases of genetically confirmed pediatric round cell tumors (10 DSRCTs, 12 Wilms tumors, 10 Ewing sarcomas, and 1 CIC-rearranged sarcoma). Immunoreactivities and immunolocalization of both the WT1 amino-terminus and carboxy-terminus were scored and documented. All DSRCTs displayed selective reactivity for only the WT1 carboxy-terminus (10/10), while dual immunoreactivity for both the WT1 carboxy-terminus (12/12) and amino-terminus antibodies (12/12) were characteristic of Wilms tumors. CIC-rearranged sarcoma showed variable WT1 nuclear immunopositivity (1/1, 1/1) and Ewing sarcomas were consistently WT1-negative for both the WT1 amino-terminus (0/10) and carboxy-terminus (0/10). Dual WT1 amino-terminus and carboxy-terminus immunohistochemistry remains a helpful diagnostic tool in discriminating intraabdominal small round cell tumors, which serves as an adjunct to the genetic information in preventing misdiagnosis.

A rare case report of renal ewing sarcoma/primitive neuroectodermal tumor with ACTH production

Background

Ewing sarcoma/primitive neuroectodermal tumor (PNET) of the renal is extremely rare. The common cause of ectopic ACTH syndrome is pulmonary neuroendocrine tumors, such as small cell carcinomas and carcinoid tumors. Here, we present an unusual case of ectopic ACTH syndrome and hypothyroidism caused by Ewing sarcoma/PNET of the right kidney.

Case presentation

A 19-year-old girl presented with a history of right lumbar pain and discomfort for 2 months, aggravated for 2 days. Abdominal contrast-enhanced computed tomography and computed tomography angiography showed an upper pole occupancy of the right kidney occupancy with subepithelial hemorrhage. Preoperative hormone levels including plasma total cortisol (PTC), adrenocorticotrophic hormone (ACTH) and thyroid hormone measurements were abnormal, indicating that the patient had Cushing syndrome and hypothyroidism. The patient underwent right radical nephrectomy. Histopathological analysis revealed a renal small round blue cell tumor (consistent with a primitive neuroectodermal tumor), with positive immunohistochemistry for CD99 and Ki67 (about 10%) and molecular pathology for EWSR1 gene fusions. PTC, ACTH and thyroid hormone returned to normal after surgery.

Conclusions

We report a rare ectopic ACTH syndrome and hypothyroidism due to renal Ewing sarcoma/PNET. The clinical manifestation of renal Ewing sarcoma/PNET is non-specific and the diagnosis relies on pathological morphology, immunohistochemistry and fusion gene detection. At present, surgery combined with radiotherapy and chemotherapy is used in the treatment, but the prognosis is still not optimistic.

Extranodal Biphenotypic Non-Hodgkin Lymphoma of the Popliteal Cavity: A Case Report and Review of Literature

Primary soft-tissue lymphoma (PSTL) is a rare extranodal non-Hodgkin lymphoma, characterized by a mass growing within soft-tissue, which is connective tissue, adipose tissue, and skeletal muscle. Here, we describe a case of biphenotypic lymphoblastic lymphoma arising from soft tissue of the popliteal fossa in an 11-year-old boy. A pediatric review about PSTL revealed that anaplastic large cell lymphoma is the most common histological type and a biphenotypic lymphoblastic lymphoma has not yet been reported in childhood. Lymphoma should always be considered in patients presenting with a soft-tissue mass, and a comprehensive immunohistochemical evaluation, including B-cell, T-cell, and myeloid markers, is needed to make a correct diagnosis and establish the most suitable treatment.

A challenging diagnosis: Lesson from case series of sacral Ewing sarcoma

Background

Ewing's sarcoma is an aggressive bone and the surrounding soft tissue cancer primarily found in children and young adults. It is mostly observed in the trunk and long bones while unusually seen in the sacrum. Sacral Ewing sarcoma has a unique anatomic limitation due to neurological structures, vertebral column, and pelvic involvement. Hence, identifying sacral Ewing's sarcoma remains a challenge.

Method

This is a case series including three patients diagnosed with Sacral Ewing's sarcoma. These three cases have been diagnosed based on clinical and radiographic examination, MRI, histopathology, and immunohistochemistry examination.

Discussion

Sacral Ewing's sarcoma remains a challenge to diagnose due to its unique anatomy site. MRI examination is sensitive to detect lesions but nonspecific. Thus, require histopathological confirmation.

Conclusion

Early diagnosis of Ewing's sarcoma is essential and we need to perform further examinations, such as immunohistochemistry examination, to confirm the diagnosis of Ewing's sarcoma.

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Sacral Ewing's sarcoma remains a challenge to diagnose due to its unique anatomy site.

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MRI examination is sensitive to detect lesions but nonspecific.

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We recommended to perform further examinations, such as immunohistochemistry examination, to confirm the diagnosis of Ewing’s sarcoma.

Case Report: Primary Intraosseous Poorly Differentiated Synovial Sarcoma of the Femur

Primary intraosseous poorly differentiated synovial sarcoma is exceedingly rare. Here, we present a case of primary intraosseous poorly differentiated synovial sarcoma from the proximal femur in a 16-year-old girl. The case was initially misdiagnosed, but the correct diagnosis of synovial sarcoma was eventually confirmed by fluorescence in situ hybridization and next-generation sequencing. We review the literature pertaining to synovial sarcoma and show that this case is the second molecularly proven intraosseous poorly differentiated synovial sarcoma in the literature. Recognition of intraosseous synovial sarcoma composed of small round cells is imperative in order to avoid misdiagnosis of the tumor as Ewing sarcoma and other small round-cell tumors, all of which have markedly different clinical management.

Rare case of renal Ewing sarcoma presenting as ectopic Cushing syndrome in a 12-year-old girl

We present a 12-year-old girl with recent onset weight gain and purple striae over the abdomen. Examination revealed her to be hypertensive. On evaluation for Cushing syndrome (CS), her cortisol and adrenocorticotropic hormone (ACTH) were found to be high. MRI brain showed a suspicious lesion (thought to be pituitary microadenoma). Inferior petrosal sinus sampling was not conclusive of pituitary source of ACTH. High dose dexamethasone suppression test confirmed an ectopic source of ACTH secretion and CT scan revealed a mass in the right kidney which was laparoscopically excised. Histopathology and immunohistochemistry confirmed Ewing sarcoma. Our case highlights the rare presentation of renal Ewing sarcoma (RES) as CS. To the best of our knowledge, this is only the second case report of RES/primitive neuroectodermal tumour of the kidney presenting as CS in paediatric age group and first with a concomitant pituitary incidentaloma.

Diagnosis of soft tissue tumors using immunohistochemistry as a surrogate for recurrent fusion oncoproteins

Soft tissue neoplasms encompass a broad spectrum of clinicopathologic manifestations. In a subset of soft tissue tumors, spanning a wide range of clinical behavior from indolent to highly aggressive, recurrent genetic translocations yield oncogenic fusion proteins that drive neoplastic growth. Beyond functioning as primary mechanisms of tumorigenesis, recurrent translocations represent key diagnostic features insofar as the presence of a particular oncogenic gene fusion generally points to specific tumor entities. In addition to more direct methods for identifying recurrent translocations, such as conventional cytogenetics or fluorescence in situ hybridization, immunohistochemistry for a component of the fusion oncoprotein increasingly is being used as a surrogate marker, exploiting the tendency of these fusion components to be distinctively overexpressed by translocation-bearing tumor cells. Diagnostic immunohistochemistry can also be used to identify the characteristic gene expression changes that occur downstream of oncogenic fusions. Here, we review the use of immunohistochemistry to detect surrogate markers of recurrent translocations in soft tissue tumors, focusing on the practical applications and limitations of this diagnostic approach.

Successful Radical Pneumonectomy for a Primitive Neuroendodermal Tumor in the Lung: A Case Report and Review of the Literature

Peripheral primitive neuroendodermal tumors (PNETs) and Ewing's sarcoma belong to the Ewing family of tumors and are small round-cell malignancies originating from spinal cord cells. These tumors account for 5% of all small round-cell malignant neoplasms. PNETs that arise from the lung parenchyma without pleural or chest wall involvement are very rare. We report a case of an adult female with a large pulmonary PNET who had given birth just 1 month prior to the diagnosis. She had cough and expectoration for 6 months, and the preoperative examination showed no metastases. Thus, we performed radical pneumonectomy and lymph node dissection. The patient recovered well without surgical complications and was discharged 7 days after the surgery. Postoperative pathology confirmed that the tumor was a small round-cell malignancy, and the tumor cells were positive for CD99, Friend leukemia virus integration 1 (FLI-1), and neuron-specific enolase (NSE), which was consistent with the diagnosis of a PNET. For primary large pulmonary PNETs, radical pneumonectomy may be a safe surgical method, worthy of further application in clinical practice.

[New in the current WHO classification (2020) for soft tissue sarcomas]

The current WHO classification for tumors of soft tissue and bone includes numerous new entities, most often defined by novel molecular findings. In this article, we present translocation-positive tumors to broaden the spectrum of monomorphic mesenchymal neoplasias. The undifferentiated small round cell sarcomas are now assembled in their own separate chapter to underline their occurrence in both soft tissue and bone, emphasizing their morphologic, molecular, and biologic differences. Another interesting new group are tumors with GLI1 activation, which, however, have not yet been included into the WHO classification. NTRK-driven tumors present with a potential therapeutic target for several established inhibitors. Finally, there have been novel findings in rhabdomyosarcomas allowing more precise subtyping associated with different biological behavior.

DDIT3 Immunohistochemistry Is a Useful Tool for the Diagnosis of Myxoid Liposarcoma

Myxoid liposarcoma is a malignant adipogenic neoplasm characterized by prominent arborizing capillaries, occasional lipoblasts, and primitive-appearing spindle cells in a myxoid background. A recurrent translocation in myxoid liposarcoma results in an oncoprotein consisting of full-length DDIT3 (CHOP) fused to an N-terminal segment of either FUS (TLS) or, less often, EWSR1. Here, we explore the diagnostic significance of DDIT3 expression in myxoid liposarcoma using a mouse monoclonal antibody recognizing an epitope in the N-terminal region. Studying a total of 300 tumors, we find diffuse, moderate-to-strong nuclear-localized anti-DDIT3 immunoreactivity in all 46 cases of myxoid liposarcoma representing 36 unique tumors, including 6 cases with high-grade (round cell) morphology. DDIT3 immunohistochemistry also highlighted a distinctive vasculocentric growth pattern in 7 myxoid liposarcomas treated with neoadjuvant radiation. In contrast, the vast majority of other examined lipomatous and myxoid neoplasms exhibited no DDIT3 expression; limited, weak immunoreactivity in <10% of cells was infrequently observed in dedifferentiated liposarcoma (6/39, 15%), solitary fibrous tumor (3/12, 25%), pleomorphic liposarcoma (1/15, 7%), and high-grade myxofibrosarcoma (2/17, 12%). Although this minimal DDIT3 expression did not correlate with DDIT3 amplification or myxoid liposarcoma-like morphology in dedifferentiated liposarcoma, there was evidence among sarcomas (excluding myxoid liposarcoma) of a relationship between expression and exposure to neoadjuvant radiation or cytotoxic chemotherapy. The constellation of findings indicates that DDIT3 immunohistochemistry may have utility in the evaluation of myxoid and lipomatous neoplasms to support the diagnosis of myxoid liposarcoma.

Primary Ewings sarcoma in liver - A rare case report with review of literature

Ewing's sarcoma family of tumours include both peripheral primitive neuroectodermal tumour (PNET) and Ewing's sarcoma including both intraosseous and extra osseous sites. Rarest of all is the involvement of liver as primary site, of which only 4 case reports have been published. We report a very rare case of 4 year old male child with primary Ewing's Sarcoma in the liver along with review of literature. The child presented with pain abdomen and low grade fever and hepatomegaly. On putting extensive IHC panel on liver SOL biopsy the small round cells were positive for FLI-1 & CD99 & were immunonegative for OCH, LCA, AFP, WT1, NSE, MYOGENIN, B-catenin & glypican 3. The histopathological and immunohistochemical profile was suggestive of Ewing's Sarcoma. To our knowledge, this is the fifth reported case of Ewing's Sarcoma occurring in liver as primary & first case to be present in a young boy of 4 years age.

Western Blot Analysis in Ewing Sarcoma

Western blot is an experimental method used to analyze protein expression. In Ewing sarcoma, as in many other diseases, Western blot provides information about the level of protein expression in different cell conditions, in comparison with other tissues or upon induced molecular changes. Based on the specific pattern of protein expression of the tissue, as well as on the characteristics of the protein of interest, the antibodies and protocol of Western blot may be modified according to different specifications. Here we describe some of these peculiarities in frame of Ewing sarcoma field.

(Immuno)histological Analysis of Ewing Sarcoma

The diagnosis of Ewing sarcoma requires the integration of the information generated from numerous techniques, some of them being very sophisticated. However, the first steps of the diagnostic process are crucial to achieve the maximum possible diagnostic performance. In this chapter we will review how to handle the diagnostic specimen from its collection, how to prepare it for diagnosis, how to make a complete pathology report, and provide guidance for the reasonable use of immunohistochemical techniques in this malignancy.

Experience with Orbital Tumors from a Tertiary Cancer Centre of North East India: A Pathology Perspective

Background  The orbit is an anatomically complex structure comprising the globe, extraocular muscles, fat, vascular, nervous, glandular, and connective tissues. A wide variety of neoplasms can arise from different orbital structures, which can create a diagnostic challenge to the pathologists. No formal study has been conducted in this regard in North East India. Aim and Objectives  This article aims to document the pattern and prevalence of orbital tumors in our institute and assess the utility of histopathological examination (HPE) and immunohistochemistry (IHC) in the precise diagnosis of these neoplasms. Materials and Methods  A retrospective analysis of orbital tumors was performed over a period of 5 years from 2013 to 2018 in the department of pathology at a tertiary cancer center of North East India following all the guidelines of the institutional ethics committee. Results  A total of 35 cases of orbital neoplasms, evaluated by HPE and IHC, were found, all of them being malignant tumors. The age range was 4 months to 85 years. Male to female ratio was 1.5:1. The most common tumor found was lymphoma, accounting for 10 cases (28.6%), all of which were non-Hodgkin lymphoma (NHL). All these cases except one occurred in adults, thus making it the most common tumor in adults in this study. Diffuse large B cell lymphoma, not otherwise specified, was the most common NHL, followed by follicular lymphoma, mature T cell NHL, extranodal marginal zone lymphoma, and B cell lymphoblastic lymphoma. Rhabdomyosarcoma and poorly differentiated/undifferentiated carcinoma jointly were the second most common tumors, totaling seven cases (21.21%) each. This was followed by melanoma (three cases), myeloid sarcoma (three cases), Ewing sarcoma/peripheral neuroectodermal tumor (PNET) (three cases), neuroblastoma (one case), and angiosarcoma (one case). Among these, rhabdomyosarcoma, granulocytic sarcoma, Ewing sarcoma/PNET, and neuroblastoma exclusively troubled the children. IHC markers including the lymphoma panel, and soft tissue ones were crucial in the precise diagnosis of the neoplasms encountered. Conclusion  A variety of malignant orbital tumors may be seen in clinical practice. Management of these tumors requires a multidisciplinary approach. HPE in conjunction with IHC evaluation is of utmost importance in the veracious recognition of orbital tumors for their proper management.

Do Primitive Neuroectodermal Tumors of the Kidney Have a Predilection for Inferior Vena Cava Involvement? A Case Series and Review of the Literature

The primitive neuroectodermal tumor (PNET) of the kidney is an extremely rare neoplasm, the diagnosis of which mainly depends upon histopathology, immunohistochemistry (IHC), and cytogenetics. A handful of cases reported in the literature mention about aggressive features of this neoplasm. The purpose of our study was to review our experience in not only the diagnosis and management of the patients with renal PNET but also to highlight its propensity to involve inferior vena cava (IVC) and also present a rare occurrence of Ewing's sarcoma (ES)/PNET of the renal pelvis. The clinical, operative, and histopathology records of four patients of renal PNET treated between January 2017 and December 2019 were reviewed and data analyzed concerning the available literature. Out of the four patients treated, two had level III and IV IVC thrombus, and one had dense desmoplastic adhesions with the IVC wall. One of the cases had a rare presentation of ES/PNET of the renal pelvis. All patients were managed surgically, while only one patient received adjuvant chemotherapy and following up with remission for the last 2 years and 4 months. On IHC, cluster of differentiation-99 (CD-99) was positive in all patients, and three were positive for Friend leukemia integration-1. PNET of the kidney is primarily an immunohistopathological diagnosis. This neoplasm has an increased propensity for the local invasion of surrounding structures. A multimodality approach with surgery, chemotherapy, and radiotherapy could offer better outcomes, although the prognosis of these tumors remains poor.

Primary Ewing sarcoma/primitive neuroectodermal tumor of the lung

We present the autopsy findings and differential diagnosis in a 42year old male who presented with fever and rapidly progressive respiratory symptoms like breathlessness, nonproductive cough and right sided chest pain. Initial imaging workup done at our hospital revealed a large unilateral tumor with tracheal shift. While being evaluated patient developed facial puffiness, tachypnea suggestive of superior vena cava obstruction. Antemortem biopsy of lung mass was attempted twice and that suggested malignant lesion. Unfortunately, the individual had a rapid downhill course following admission. Post mortem examination was conducted that on opening the thoracic cavity revealed total replacement of right lung tissue by a necrotic growth which was deeply adherent to the rib cage. The contralateral lung as well as all other visceral organs were unremarkable grossly. Histopathology confirmed primary Ewing sarcoma of the lung. We hereby, report a rare case of primary lung Ewing sarcoma diagnosed at autopsy.

Primary round cell sarcomas of the urinary bladder with EWSR1 rearrangement: a multi-institutional study of thirteen cases with a review of the literature

Primary Ewing sarcoma (ES) of the urinary bladder is a rare and aggressive small blue round cell malignant neoplasm associated primarily with translocation involving EWSR1 and FLI1 genes located in the 22nd and 11th chromosomes, respectively. To date, 18 cases have been published in the literature as single-case reports, based chiefly on CD99 positivity (17 patients). Molecular confirmation by fluorescence in situ hybridization was performed in 9 patients, and FLI1 immunohistochemical (IHC) analysis was not performed in any of these published cases. Herein, we present thirteen patients of more comprehensive primary round cell sarcomas of the urinary bladder with EWSR1 rearrangement. Clinicopathologic parameters including demographics; clinical presentation; histopathologic, IHC, and molecular profiles; and management and follow-up data of 13 patients with primary round cell sarcomas with EWSR1 rearrangement (Ewing family of tumor) of the urinary bladder were analyzed. The studied patients (n = 13) included 6 females and 7 males; their age ranged from 4 years to 81 years (median = 30 years). The most common clinical presentation was hematuria (n = 7), followed by hydronephrosis (n = 2, one with renal failure). The tumor size ranged from 2.9 cm to 15 cm in maximum dimension. Conventional ES architecture and histology was observed in 6 cases, and diverse histology was observed in 7 cases (adamantinomatous pattern [n = 1], alveolar pattern [n = 1], ganglioneuroblastoma-like pattern [n = 2], and small cell carcinoma-like pattern [n = 3]). All the tumors were muscle invasive (invasion into the muscularis propria). IHC analysis showed that all tumors expressed FLI1, CD99, and at least one neuroendocrine marker. Focal cytokeratin staining was positive in 2 patients, and RB1 was retained in all patients. EWSR1 rearrangement was seen in 12 of 12 tumors (in 12 patients) tested. A combined multimodal approach that included surgery with chemotherapy was instituted in all patients. Follow-up was available for 11 patients (ranging from 5 to 24 months). Six patients either died of disease (n = 3) or other causes (n = 3). Five patients were alive with metastases to the liver (n = 1), liver and lung (n = 2), liver and abdominal wall (n = 1), and kidney (n = 1). Based on our experience with the largest series to date and aggregate of the published data, ES/round cell sarcomas with EWSR1 rearrangement occurring in the bladder have bimodal age distribution with poor prognosis despite aggressive therapy. Owing to its rarity and age distribution, the differential diagnosis is wide and requires a systematic approach for ruling out key age-dependent differential diagnoses aided with molecular confirmation.

Primary cutaneous Ewing sarcoma with diffuse S100/SOX10 positivity and pseudoalveolar pattern: An extraordinarily rare case highlighting a potential pitfall with significant repercussions

Primary cutaneous Ewing sarcoma is a very rare entity with less than 100 cases reported in the literature, sharing the same morphological and immunohistochemical characteristics as their osseous counterparts. Herein, to the best of our knowledge, we report the first case in English literature of a molecularly confirmed Ewing sarcoma with diffuse and strong SOX10 immunoreactivity. This exceedingly rare immunohistochemical finding along with the rarity of this tumor could easily lead to a misdiagnosis with significant repercussions. Our case highlights the difficulty in diagnosing primary cutaneous Ewing sarcoma as well as the pivotal role molecular diagnostics can play in specific scenarios.

Danger is only skin deep: aggressive epidermal carcinomas. An overview of the diagnosis, demographics, molecular-genetics, staging, prognostic biomarkers, and therapeutic advances in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a high grade primary cutaneous neuroendocrine carcinoma and is among the most aggressive cutaneous malignancies. The rising incidence of MCC, together with its often rapidly aggressive course, underscore a critical need to recognize the histopathologic and the immunohistochemical features that inform its accurate diagnosis. In the current review, we summarize the current state of knowledge regarding the accurate diagnosis of MCC and the exclusion of other entities in the differential diagnosis. We provide a comprehensive review of genomic studies that identified the molecular-genetic drivers of MCC as well as a summary of studies identifying prognostic biomarkers that can facilitate risk stratification. Importantly, Merkel cell polyomavirus (MCPyV) appears to be causative in most cases of MCC and represents both a diagnostic and prognostic marker. Finally, as staging of MCC has undergone critical refinements with the introduction of the 8th Edition of the American Joint Committee on Cancer staging system, we provide an update on MCC staging. In particular, the prognostic significance of the sentinel lymph node (SLN) in MCC necessitates a systematic approach to its evaluation and diagnosis to ensure accurate and consistent risk stratification for patients, and we therefore provide a comprehensive overview of SLN evaluation in MCC. Finally, the intimate relationship between MCC and the integrity of the host immune system has led to paradigm-shifting therapeutic advances with the successful application of immune checkpoint blockade to treat patients with advanced disease, and we therefore summarize those studies and the correlative studies in which predictive biomarkers have been identified.

Ewing Sarcoma With Emphasis on Extra-skeletal Ewing Sarcoma: A Decade's Experience From a Single Centre in India

INTRODUCTION

The diagnosis of Ewing sarcoma family of tumours (ESFT) is challenging, especially in adults and in extra-skeletal or visceral location. Several morphologic mimics with varied treatment options and prognosis confer diagnostic dilemmas. Application of ancillary diagnostic modalities in surgical pathology in clinical routine has enabled accurate diagnosis of ESFT in bone, soft tissues, and viscera.

AIM

The study aims to assess the clinicopathological features including molecular test results of ESFT with emphasis on sex, age, and location, especially extra-skeletal soft tissue and visceral location.

MATERIAL AND METHODS

Data of clinicopathological, molecular tests (wherever performed), diagnosis rendered in 302 ESFT over a decade from our centre were reviewed. Statistical comparison of skeletal and extra-skeletal tumours with reference to age and sex was done using SPSS package. The P value of <.05 was considered significant.

RESULTS

The cohort included 302 ESFTs with 49% skeletal and 51% extra-skeletal tumours. Thigh was most common site among skeletal tumours; chest wall, paraspinal location, and retroperitoneum among soft tissues (39.4%); and kidney, ovary, and cervix among visceral tumours (11.3%). Fluorescence in situ hybridisation for EWSR1 gene rearrangement was positive in 54 patients and reverse-transcriptase polymerase chain reaction in 19 patients. Predominance of male sex, younger age and location in extremities among skeletal tumours and lack of gender predilection, higher age and axial location in extra-skeletal tumours were noted, which were statistically significant. Molecular tests were performed more frequently in extra-skeletal tumours, especially in visceral tumours to establish the diagnosis.

CONCLUSIONS

The study showed statistically significant differences in the age, sex, and location between skeletal and extra-skeletal ESFT. The increased percentage of extra-skeletal tumours especially in viscera was attributed to the increased awareness and availability of ancillary techniques.

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.

Treatment Outcomes of Pediatric Patients With Ewing Sarcoma in a War-Torn Nation: A Single-Institute Experience From Iraq

PURPOSE

Ewing sarcoma (ES) is a relatively rare, highly malignant tumor of the musculoskeletal system. It is the second most common malignant bone tumor in children and adolescents in the age group of 5 to 20 years. The aim of this study was to identify the treatment outcomes of pediatric patients with ES in Sulaimani governorate, Iraq.

PATIENTS AND METHODS

This was a retrospective study that reviewed the medical records of pediatric patients with ES who were managed between 2009 and 2015, with follow-up until late 2017. Patient- and tumor-related factors were correlated with clinical outcomes.

RESULTS

A total of 31 pediatric patients with ES were included in this study. All the patients received chemotherapy and radiotherapy, whereas only 14 patients underwent surgical resection and just eight had free surgical margins. The median age at diagnosis was 13 years, 58% were male, and 42% were female. The presenting symptoms at diagnosis were mostly pain (67.7%) and palpable mass (25.8%). The primary tumor was located in the extremities (51.6%), the thoracic cage (19.4%), the pelvis (16.1%), and the lumbar vertebrae (12.9%). Approximately two thirds of the patients (61.3%) had localized disease at the time of presentation. The 5-year overall survival was 19%, and the 5-year recurrence-free survival was 34%.

CONCLUSION

Clinical outcomes of ES in pediatric patients in our war-torn nation, Iraq, are still markedly inferior to the published outcomes from stable, developed nations. Additional large and multicenter national studies are required. Diagnostic and therapeutic measures need improvement, and multidisciplinary and comprehensive cancer-integrated approaches are vital for better outcomes.

A case of primary cutaneous Ewing sarcoma in a neutropenic patient

Primary cutaneous Ewing sarcoma is a rare clinical presentation of Ewing sarcoma, usually occurring as a small, localized tumor on the extremities of young adults and associated with favorable prognosis. We report a case of primary cutaneous Ewing sarcoma, which presented on the sole of the foot of a 27-year-old patient with relapsed acute myeloid leukemia and neutropenia. Diagnosis was determined through histological features and staining, as well as fluorescence in situ hybridization and molecular testing. The patient underwent wide-local excision with plan to begin targeted chemotherapy, but unfortunately died from adenovirus pneumonia while neutropenic before targeted chemotherapy was initiated.

Clinical Features and Long-Term Outcome of Primary Intracranial Ewing Sarcoma/Peripheral Primitive Neuroectodermal Tumors: 14 Cases From a Single Institution

OBJECTIVE

Primary intracranial Ewing sarcoma (ES)/peripheral primitive neuroectodermal tumors (pPNETs) are extremely rare, and only a few studies have reported >4 cases of this disease. The purpose of this study was to explore the clinical features, treatment, and outcome of primary intracranial ES/pPNETs.

METHODS

The clinical data of 14 patients who had been surgically treated from February 2003 to November 2017 and in whom immunohistochemical staining results had confirmed the diagnosis of primary intracranial ES/pPNETs were retrospectively analyzed. Kaplan-Meier survival analysis was used to estimate the survival rate and the median survival time (MST).

RESULTS

Gross total resection (GTR) was achieved in 7 cases, and subtotal resection was performed in 7 cases. During follow-up, 10 (71.4%) patients had local recurrence and 3 (21.4%) patients had distant metastasis. The overall 1-, 2-, and 5-year survival rates were 78.6%, 47.6%, and 19.0%, respectively. Kaplan-Meier survival analysis showed that postoperative radiotherapy was a significant prognostic factor for longer MST (P = 0.034). GTR and radiotherapy with or without adjuvant chemotherapy yielded the highest 2-year survival rate (100%). Three patients who underwent GTR, radiotherapy, and chemotherapy had the highest 2-year survival rates (100%) and the longest MST (48 months).

CONCLUSIONS

Primary intracranial ES/pPNETs have an aggressive clinical course, with a high tendency for local recurrence and distant metastasis. Radiotherapy plays a significant role in improving the survival of patients. GTR combined with radiotherapy and chemotherapy may be the most beneficial treatment modality.

NKX2.2 immunohistochemistry in the distinction of Ewing sarcoma from cytomorphologic mimics: Diagnostic utility and pitfalls

BACKGROUND

Ewing sarcoma (ES) is a round cell sarcoma that can be challenging to diagnose on cytologic material given its significant overlap with numerous mesenchymal, epithelial, and lymphoid cytomorphologic mimics. The objective of this study was to assess the utility of a novel marker, NKX2.2, in the diagnosis of ES in cytologic material and its ability to distinguish ES from its mimics.

METHODS

NKX2.2 immunohistochemistry was performed on cell blocks from 107 fine-needle aspirations, and nuclear expression was scored semiquantitatively for extent and intensity. The study cohort included ES (n = 10), well differentiated neuroendocrine tumor (n = 20), melanoma (n = 11), Merkel cell carcinoma (n = 10), small cell carcinoma (n = 10), alveolar rhabdomyosarcoma (n = 2), spindle cell/sclerosing rhabdomyosarcoma (n = 2), synovial sarcoma (n = 12), solitary fibrous tumor (n = 2), chronic lymphocytic leukemia (n = 10), lymphoblastic lymphoma (n = 11), adenoid cystic carcinoma (n = 6), and CIC-rearranged sarcoma (n = 1).

RESULTS

NKX2.2 had high sensitivity (100%) and moderate specificity (85%) for the diagnosis of ES in cytologic material. NKX2.2 expression also was present in a subset of mesenchymal and epithelial mimics, and staining was most commonly observed in small cell carcinoma (80%) and well differentiated neuroendocrine tumor (45%). Among mesenchymal mimics, 42% exhibited NKX2.2 expression. NKX2.2 staining was absent in melanoma, adenoid cystic carcinoma, and lymphoproliferative neoplasms.

CONCLUSIONS

NKX2.2 is a highly sensitive but only moderately specific marker for ES. Neuroendocrine neoplasms exhibit variable NKX2.2 expression and remain a significant potential diagnostic pitfall. Thus, NKX2.2 expression should be interpreted in the context of an appropriate immunohistochemical panel (and often with confirmatory molecular testing) for the accurate diagnosis of ES.

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.

Comprehensive analysis of multi Ewing sarcoma microarray datasets identifies several prognosis biomarkers

Ewing sarcoma (ES) is a common primary malignancy in children and adolescents. Progression of treatment methods hasn't contributed a lot to the imrovement of prognosis. To identify potential prognostic biomarkers, a meta-analysis pipeline of multi-gene expression datasets for ES from the Gene Expression Omnibus (GEO) was performed. Three datasets were screened and differential expression genes (DEGs) in ES samples compared with normal tissues were identified through limma package and subjected to network analysis. As a result, 1,470 DEGs were obtained which were mainly involved in biological processes associated with immune response and transcription regulation. Network analysis obtained 22 core genes with high network degree and fold change. Kaplan-Meier analysis based on ES datasets from The Cancer Genome Atlas identified five genes, including glycogen phosphorylase, muscle-associated, myocyte-specific enhancer factor 2C, tripartite motif containing 63, budding uninhibited by benzimidazoses1 and Ras GTPase-activating protein 1, whose altered expression profiles are significantly associated with survival. Changes of their expression values were further confirmed through RT-qPCR in ES cell and normal cell lines. Those genes may be considered as potential prognostic biomarkers of ES and should be helpful for its early diagnosis and treatment.

Primitive neuroectodermal tumor of genital tract in hysterectomized patient: A case report

Primitive neuroectodermal tumors are high-grade malignant neoplasms. These are uncommon entities for the female genital tract. The treatment, management and follow-up period of Ewing’s tumors are not well-defined because of their rarity in the genital tract. Surgical debulking is the mainstay treatment in all cases. After debulking surgery, patients receive chemotherapy and/or radiotherapy and there is a relation between disease stage and survival. Herein, we present a case of ovarian primitive neuroectodermal tumor with a review of previously reported cases.

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.

Array-based DNA-methylation profiling in sarcomas with small blue round cell histology provides valuable diagnostic information

Undifferentiated solid tumors with small blue round cell histology and expression of CD99 mostly resemble Ewing sarcoma. However, they also may include other tumors such as mesenchymal chondrosarcoma, synovial sarcoma, or small cell osteosarcoma. Definitive classification usually requires detection of entity-specific mutations. While this approach identifies the majority of Ewing sarcomas, a subset of lesions remains unclassified and, therefore, has been termed "Ewing-like sarcomas" or small blue round cell tumors not otherwise specified. We developed an approach for further characterization of small blue round cell tumors not otherwise specified using an array-based DNA-methylation profiling approach. Data were analyzed by unsupervised clustering and t-distributed stochastic neighbor embedding analysis and compared with a reference methylation data set of 460 well-characterized prototypical sarcomas encompassing 18 subtypes. Verification was performed by additional FISH analyses, RNA sequencing from formalin-fixed paraffin-embedded material or immunohistochemical marker analyses. In a cohort of more than 1,000 tumors assumed to represent Ewing sarcomas, 30 failed to exhibit the typical EWS translocation. These tumors were subjected to methylation profiling and could be assigned to Ewing sarcoma in 14 (47%), to small blue round cell tumors with CIC alteration in 6 (20%), to small blue round cell tumors with BCOR alteration in 4 (13%), to synovial sarcoma and to malignant rhabdoid tumor in 2 cases each. One single case each was allotted to mesenchymal chondrosarcoma and adamantinoma. 12/14 tumors classified as Ewing sarcoma could be verified by demonstrating either a canonical EWS translocation evading initial testing, by identifying rare breakpoints or fusion partners. The methylation-based assignment of the remaining small blue round cell tumors not otherwise specified also could be verified by entity-specific molecular alterations in 13/16 cases. In conclusion, array-based DNA-methylation analysis of undifferentiated tumors with small blue round cell histology is a powerful tool for precisely classifying this diagnostically challenging tumor group.

Histologic Features and Prognosis of Spinal Intradural Extramedullary Ewing Sarcoma: Case Report, Literature Review, and Analysis of Prognosis

BACKGROUND

Ewing sarcoma is a malignant neoplasm that primarily involves extremity long bones, the pelvis, and soft tissues of children. The intradural extramedullary space is an uncommon location for Ewing sarcoma, and there is therefore a paucity of information regarding the features and natural history of this particular presentation. There is controversy regarding preoperative diagnosis, surgical management, and postoperative care, and there are no accepted standards.

METHODS

Herein we present a 61-year-old man with an L1-3 intradural extramedullary Ewing sarcoma who underwent gross total resection of the tumor via laminectomy. Pathologic analysis revealed a diagnosis of Ewing sarcoma based on the characteristic immunohistochemistry and the presence of EWSR1-FLI1 fusion transcript by reverse-transcription polymerase chain reaction.

RESULTS

There have been 28 cases of intradural extramedullary Ewing sarcoma reported in the literature. Out of 29 cases including the current case, 18 cases (62.1%) were men. The median and mean ages were 32 and 34.0 years, respectively, with a peak age group of 10-20 years. Twenty-two of 29 (72.4%) cases involved the lumbar spine, followed by the cervical spine (n = 7, 24.1%). Long-term prognosis was poor, with 1-, 2-, 3-, and 5-year progression-free survival rate of 75.0%, 56.3%, 37.5%, and 18.8%, respectively. The 1-, 2-, 3-, and 5-year overall survival rate was 89.5%, 80.5%, 80.5%, and 43.0%, respectively.

CONCLUSIONS

Herein, we present imaging and pathologic findings of the case with review of the literature.

Role of ancillary techniques in profiling unclassified laryngeal malignancies

Laryngeal biopsies, contrary to biopsies from many other sites of the body, very often contain minute amounts of tumour tissue that may consist of morphologically undifferentiated tumour only. In haematoxylin- and eosin-stained sections, there may be no indicative features of what specific tumour entity that is present. In the larynx, particularly small round cell neoplasms, primary or metastatic, often cause a diagnostic dilemma and where an incorrect diagnosis can induce substantial clinical consequences for the patient (e.g., primary neuroendocrine carcinomas vs metastatic variants, certain sarcomas). If sufficient/representative material has been obtained, the application of immunohistochemistry and/or molecular techniques should in virtually every case reveal the true nature of the malignancy. In cases with sparse amount of material, and therefore a limited number of sections to be cut, a careful and thoughtful stepwise approach is necessary to ascertain a reliable diagnosis, or at least guide the clinician to the most likely diagnoses. With today's advanced and widely available technology with an abundance of markers to discriminate different tumours, the use of the term "undifferentiated" should be largely unnecessary. In the exceptional, and indeed exceedingly rare cases, when a classification is not possible, even after repeat biopsy, we suggest that the laryngeal neoplasm is better termed "unclassified malignant neoplasm" rather than "undifferentiated malignant neoplasm".