Ewing Sarcoma and the History of Similar and Possibly Related Small Round Cell Tumors: From Whence Have We Come and Where are We Going?

Ewing Sarcoma of the Female Genital Tract: Clinicopathologic Analysis of 21 Cases With an Emphasis on the Differential Diagnosis of Gynecologic Round Cell, Spindle, and Epithelioid Neoplasms

Ewing sarcoma is an uncommon neoplasm considered in the differential diagnosis of tumors with "small round cell" morphology, but its occurrence in the gynecologic tract has only been sporadically documented. Herein, we describe the largest cohort of Ewing sarcoma localized to the female genital tract to date, and emphasize their clinicopathologic resemblance to more common gynecologic neoplasms. Ewing sarcoma (n=21) was retrospectively identified from 5 institutions. The average patient age was 35 (range 6-61) years. Tumor sites included uterus (n=8), cervix (n=4), vulva (n=5), vagina (n=1), broad ligament (n=1), inguinal area (n=1), and pelvis (n=1). Nine of 18 cases in which slides were available for review demonstrated only classic round cell morphology, with the remainder showing a variable combination and prominence of variant ovoid/spindle or epithelioid appearance. Tumors showed diffuse membranous reactivity for CD99 (20/20) and were positive for NKX2.2 (8/8, diffuse) and cyclin D1 (7/7, of which 3/7 were patchy/multifocal and 4/7 were diffuse). They were negative for ER (0/6) and CD10 (0/6). Three cases were initially diagnosed as endometrial stromal sarcomas. EWSR1 rearrangement was confirmed in 20/21 by fluorescence in situ hybridization (n=15) and/or sequencing (n=8). Of the eight tumors that underwent sequencing, 6 harbored FLI1 , 1 ERG, and 1 FEV as the fusion partner. Of 11 patients with available follow-up, 5 died of disease, 1 developed lung metastases and 5 are alive with no evidence of disease. Ewing sarcoma of the gynecologic tract is a rare, aggressive entity that shares some morphologic and immunohistochemical features with other more common gynecologic neoplasms. In addition to the typical round cell appearance, variant spindled/ovoid to epithelioid morphology may also be observed and should prompt consideration of this entity with appropriate immunohistochemical and/or molecular studies.

Bilateral primary ovarian Ewing sarcoma recurring as left submandibular lymphadenopathy diagnosed on cytology

Ewing sarcoma (ES) is a highly malignant and aggressive small round-cell tumor originating from primitive neuroepithelium and mesenchymal stem cells. It is usually seen in children and adolescents with a male predilection and a preponderance to occur in long bones. Although skeletal/soft tissue ES is encountered in clinical practice, primary ES of the genital tract, particularly bilateral primary ovarian ES, is highly uncommon, with only a handful of cases reported worldwide. Ovarian ES is occasionally reported to involve para-aortic and pelvic lymph nodes in advanced stages. Still, cervical lymph node metastasis from ovarian ES is an infrequent clinical occurrence and, when present, indicates a worse prognosis. Here, we present an intriguing case of bilateral peripheral primary ovarian ES in an adult female, recurring as metastasis in the left submandibular lymph node. This case underlines the importance of keeping metastasis from ES as a possible differential while diagnosing metastatic small round cell tumors in peripheral lymph nodes. It also highlights the usefulness of a minimally invasive diagnostic modality of fine needle aspiration cytology and cell block preparation with applied ancillary techniques of immunohistochemistry and confirmatory molecular testing by fluorescence in-situ hybridization (FISH), for an accurate and quick diagnosis of such entities. The cytological diagnosis of our patient helped in the prompt and early initiation of chemotherapy without requiring any invasive procedure.

Ewing's sarcoma of the head and neck: A systematic review

OBJECTIVE

The aim of the present study was to conduct a systematic review of head and neck Ewing sarcoma (ES) concerning patients' demographic and clinical features, histopathological findings, treatment, follow-up, and survival rate.

MATERIALS AND METHODS

An electronic search was undertaken in four databases. Articles describing case reports or case series were included. Outcomes were evaluated by the Kaplan-Meier method along with Cox regression.

RESULTS

The search yielded 186 studies describing 227 ES cases. The mean age was 22.7 years, and males were slightly more affected. Interestingly, more than half the cases were diagnosed up to 20 years. The respiratory tract was the most reported site, followed by the jawbones. Clinically, symptomatic swelling or nodules were described, with a mean duration of 4 months. Management involved multimodal treatment regimens. Local recurrence, lymph node and distant metastasis were observed in 10.7%, 12.6%, and 20.3% of cases, respectively. Statistical analysis revealed that older patients with distant metastasis had a lower overall survival rate (p < 0.05).

CONCLUSION

This study provides an overall view of head and neck ES that can assist oral and maxillofacial pathologists with the diagnosis and extend the knowledge of surgeons and oncologists about this condition.

Keeping it real: Merging traditional and contemporary practices in musculoskeletal pathology: A special issue of neoplastic and non-neoplastic bone and soft tissue pathology

There is no shortage of comprehensive review articles on bone and soft tissue pathology, almost always representing a regurgitation of the literature with little to no guidance on personal "best practices," recommended applications of ancillary testing, and alternative points of view. This special issue of Human Pathology uniquely unites evidence-based medicine, where appropriate, with the collective personal experiences of a wide range of accomplished pathologists from varying institutions and backgrounds, addressing problematic areas, updated and sometimes imperfect classification systems, and their personal preferences for cost-effectively incorporating ancillary testing. For the preponderance of general pathologists (and specialists), whether academic or non-academic, non-neoplastic musculoskeletal diseases represent a far higher percentage of their practice than bone and soft tissue neoplasia. One of the most common frozen sections performed at many hospitals throughout the USA is revision arthroplasty, relying on the pathologist to help determine the presence (or absence) of periprosthetic joint infection, largely based on the hematoxylin & eosin (H&E) slide. Not every institution has access to the latest molecular techniques; fortunately, many of the current immunohistochemical antibodies serve as reliable surrogate markers of genetic mutations, allowing for cheaper but accurate diagnoses, when deemed necessary. Furthermore, molecular testing is often not necessary to establish a specific diagnosis, even among neoplasms with known underlying genetic abnormalities. It must be remembered that most bone and soft tissue tumors were recognized and classified correctly, before we uncovered and understood, among a subset, their underlying and unique molecular aberrations. Perhaps not surprisingly, in some cases, more than one molecular pathway may lead to the same histologic tumor subtype. Less commonly, an identical genetic driver/fusion may result in immunophenotypically and biologically distinct neoplasms, sometimes with entirely different clinical behaviors. "Dedifferentiation," a concept recognized among a variety of bone and soft tissue neoplasms, including but not limited to chondrosarcoma, parosteal osteosarcoma, and liposarcoma, needs to be objectively reassessed, particularly for liposarcoma. The following reviews attempt to address the above concepts, re-emphasizing the important role the practicing pathologist continues to (and must) play in the differential diagnoses of neoplastic and non-neoplastic musculoskeletal diseases.

Malignant tumour in pregnancy: Ewing-like sarcoma of the gluteal region

We report a case of an Ewing-like sarcoma of the gluteal region with ongoing growth during the second trimester of pregnancy and noted during the third trimester. This lesion was consequently studied to infer its malignant potential. Several examinations were conducted to characterise this lesion, such as ultrasound and MR, which showed signs of tumourous invasion of the deep tissues of the gluteal region.Given that the pregnancy was at the end of the third trimester, the decision was made to schedule the delivery at 37 weeks of gestation and treat the tumour afterwards to balance maternal and fetal health.This case illustrates the need for a detailed investigation and guidance by a multidisciplinary team to provide prenatal counselling regarding a malignant tumour during pregnancy.

Ewing sarcoma of the pancreas: a pediatric case report and narrative literature review

Ewing's Sarcoma (ES) is an rare, small round-cell sarcoma that predominantly occurs in children and young adults, with both skeletal and extraskeletal manifestations. However, pancreatic ES, due to its rarity, is infrequently featured in scholarly literature, with only a scant 43 reported instances. Our study describes a case of pancreatic ES in an 8-year-old boy who was found to have an abdominal mass. Following an exhaustive examination, the boy was diagnosed with a neoplasm in the pancreatic head and underwent a complex surgical procedure encompassing pancreatoduodenectomy and partial transverse colectomy. Immunohistochemical assays confirmed the neoplastic cells' positivity for Cluster of Differentiation 99(CD99), Vimentin, and NK2 Homeobox 2(NKX2.2), while genomic testing identified an EWSR1-FLI1(Ewing Sarcoma Breakpoint Region 1-Friend Leukemia Integration 1) gene fusion. This led to a conclusive diagnosis of pancreatic Ewing's Sarcoma. The patient underwent seven cycles of adjuvant chemotherapy, alternating between VDC (Vincristine, Doxorubicin, Cyclophosphamide) and IE (Ifosfamide, Etoposide) tri-weekly, but did not undergo radiotherapy. At present, the patient remains neoplasm-free. Through our case analysis and comprehensive review of the existing literature, we aim to underscore th rarity of pancreatic Ewing's sarcoma and to highlight the efficacy of our individualized therapeutic approach.

Sclerosing Epithelioid Fibrosarcoma

Sclerosing epithelioid fibrosarcoma (SEF) is a distinctive sarcoma that may arise in nearly any soft tissue site or bone. While there has been past controversy as to whether it is related to low-grade fibromyxoid sarcoma (LGFMS), it has been shown to behave far more aggressively than LGFMS. SEF has a propensity to metastasize to the lungs and bone and arise within the abdominal cavity. Histologically, it is characterized by uniform nuclei embedded in a densely collagenous stroma simulating osteoid. By immunohistochemistry, it is often strongly positive for MUC4. The majority (75%) have EWSR1 gene rearrangement, most commonly with CREB3L1 as a fusion partner, although a variety of FUS/EWSR1 and CREB3L1/CREB3L2/CREB3L3 fusions have been described in addition to others. SEF is currently recalcitrant to nearly all chemotherapy and radiation therapy.

Ewing's sarcoma in a young man mimicking lateral elbow pain: A case report with 2 years follow-up

BACKGROUND AND PURPOSE

Lateral elbow pain represents a common musculoskeletal disorder, mostly non-specific and benign. In rare cases, it can be the first symptom of a severe disease such as Ewing's sarcoma (ES). ES is the second most common primary malignant bone tumor in the young population, with a high probability of an unfavourable prognosis.

CASE PRESENTATION

This case report presents the history of a young man presenting to the physical therapist with a diagnosis of "epicondylitis" in the right elbow, which was later revealed to be an aggressive ES of the ulna. Findings raising clinical doubts were (a) constant pain even at night and not dependent on load, (b) significant loss of function, (c) patient's young age, and (d) a palpable mass in the elbow.

RESULTS

After diagnosis, the patient received medical (chemotherapy, radiotherapy and surgery) and a rehabilitation program. After treatment, the patient improved elbow function, decreased disability and returned to social participation, maintaining positive outcomes at the 2-year follow-up.

DISCUSSION

In summary, this case report emphasizes the importance of differential diagnosis and screening for referral of red flags in physical therapy. Moreover, it describes the rehabilitation of a patient with ES, enriching the scientific literature in the field.

Mandibular small cell osteosarcoma: a case report and review of literature

BACKGROUND

Small cell osteosarcoma is an extremely rare histopathological variant of conventional osteosarcoma. Due to nonspecific symptoms, most osteosarcomas of the jaws are misdiagnosed as periapical abscesses and mistreated by teeth extraction and drainage.

CASE PRESENTATION

We report, to our knowledge, the seventh case of small cell osteosarcoma in gnathic sites affecting the mandible of an old female with history of a large painful swelling related to the right mandibular molar area for 2 months. Cone-beam computed tomography scan showed an osteolytic lesion related to the lower molar area with involvement of the inferior alveolar nerve. An incisional biopsy was taken, and after histopathological examination and immunohistochemical staining, a diagnosis of small cell osteosarcoma was reached. Hemi-mandibulectomy was performed by a maxillofacial surgeon. No clinical evidence for recurrence was noted until manuscript writing.

CONCLUSION

Accurate diagnosis is very important, and general practitioners should be aware of this entity considering that small cell osteosarcoma has a poor prognosis when compared to conventional osteosarcoma.

Routine EWS Fusion Analysis in the Oncology Clinic to Identify Cancer-Specific Peptide Sequence Patterns That Span Breakpoints in Ewing Sarcoma and DSRCT

(1) Background: EWS fusion genes are associated with Ewing sarcoma and other Ewing family tumors including desmoplastic small round tumor, DSRCT. We utilize a clinical genomics workflow to reveal real-world frequencies of EWS fusion events, cataloging events that are similar, or divergent at the EWS breakpoint. (2) Methods: EWS fusion events from our next-generation sequencing panel (NGS) samples were first sorted by breakpoint or fusion junctions to map out the frequency of breakpoints. Fusion results were illustrated as in-frame fusion peptides involving EWS and a partner gene. (3) Results: From 2471 patient pool samples for fusion analysis at the Cleveland Clinic Molecular Pathology Laboratory, we identified 182 fusion samples evolved with the EWS gene. They are clustered in several breakpoints: chr22:29683123 (65.9%), and chr22:29688595 (2.7%). About 3/4 of Ewing sarcoma and DSRCT tumors have an identical EWS breakpoint motif at Exon 7 (SQQSSSYGQQ-) fused to a specific part of FLI1 (NPSYDSVRRG or-SSLLAYNTSS), ERG (NLPYEPPRRS), FEV (NPVGDGLFKD) or WT1 (SEKPYQCDFK). Our method also worked with Caris transcriptome data, too. Our primary clinical utility is to use this information to identify neoantigens for therapeutic purposes. (4) Conclusions and future perspectives: our method allows interpretation of what peptides result from the in-frame translation of EWS fusion junctions. These sequences, coupled with HLA-peptide binding data, are used to identify potential sequences of cancer-specific immunogenic peptides for Ewing sarcoma or DSRCT patients. This information may also be useful for immune monitoring (e.g., circulating T-cells with fusion-peptide specificity) to detect vaccine candidates, responses, or residual disease.

Testicular Tumors: New Developments in Germ Cell and Sex Cord Stromal Tumors

This article reviews the recent advances and potential future changes in the classification of testicular germ cell and sex cord stromal tumors, highlighting changes in the classification system and terminology with description on newer entities. A discussion on approaching difficult areas and diagnostic pitfalls is also included along with the utility of ancillary investigations. Areas with limited knowledge are highlighted to providing direction for future studies and a bulleted summary in the form of critical care points is provided.

Ewing Sarcoma of the Lung: Imaging of a Rare Tumor

Primary pulmonary Ewing sarcoma is an extremely rare tumor of neuroectodermal tissue. In this article, we report on the case of a 45-year-old female who presented in the emergency department with shortness of breath and night fever. Radiologic findings suggested a massive pulmonary mass and a metastatic liver lesion. The diagnosis of Ewing sarcoma was established through a percutaneous biopsy of the lung mass and liver lesion. We highlight the importance of considering a broad differential diagnosis for a large pulmonary mass in order to lead to a prompt diagnosis and treatment.

An introduction to the WHO 5th edition 2022 classification of testicular tumours

The 5th edition of the World Health Organisation Blue Book was published recently and includes a comprehensive update on testicular tumours. This builds upon the work of the 4th edition, retaining its structure and main nomenclature, including the use of the term 'germ cell neoplasia in situ' (GCNIS) for the pre-invasive lesion of most germ cell tumours and division from those not derived from GCNIS. While there have been important developments in understanding the molecular underpinnings of testicular cancer, this updated classification paradigm and approach remains rooted in morphology. Nomenclature changes include replacement of the term 'primitive neuroectodermal tumour' by 'embryonic neuroectodermal tumour' based on the non-specificity of the former term and to separate these tumours clearly from Ewing sarcoma. Seminoma is placed in a germinoma family of tumours emphasising relation to those tumours at other sites. Criteria for the diagnosis of 'teratoma with somatic transformation' have been modified to not include variable field size assessments. The word 'carcinoid' has been changed to 'neuroendocrine tumour', with most examples in the testis now classified as 'prepubertal type testicular neuroendocrine tumour'. For sex cord-stromal tumours, the use of mitotic counts per high-power field has been changed to per mm2 for malignancy assessments, and the new entities, 'signet ring stromal tumour' and 'myoid gonadal stromal tumour', are defined. Well-differentiated papillary mesothelial tumour has now been defined as tumour type with a favourable prognosis. Sertoliform cystadenoma has been removed as an entity from testicular adnexal tumours and placed with Sertoli cell tumours.

Malignant Superficial Mesenchymal Tumors in Children

Malignant superficial mesenchymal tumors are a very diverse group of neoplasms with few clinical and radiological discriminatory factors. Hence, some of these cancers are rarely suspected based on clinical and radiological grounds, others may be easily misdiagnosed, and the histological analysis of a biopsy or resection is central in the diagnostic process. In children, the age at presentation is a major element of the differential diagnosis. Some tumors have a very distinct epidemiology, while others may be seen at any age. More recently, the advances in molecular biology have greatly improved the diagnosis of mesenchymal tumors and new entities are still being described. In the present review, we provide an overview of the diversity of malignant superficial mesenchymal tumors in children, including new and/or rare entities. We discuss the important diagnostic features, be they clinical, histological, or molecular. Special attention was given to the genetic features of these tumors, particularly when they were helpful for the diagnosis or treatment.

Primary Pulmonary Round Cell Sarcomas: Multiple Potential Pitfalls for the Pathologist

Primary sarcomas of the lung are extremely uncommon. A diverse group of round cell sarcomas has been reported to originate in this location, including Ewing sarcoma, desmoplastic small round cell tumor, rhabdomyosarcoma, and poorly differentiated synovial sarcoma. The rarity of these tumors presents a potential pitfall; without careful study, they may easily be misidentified as the significantly more common poorly differentiated carcinoma. While histomorphology is a key aspect of correctly identifying a sarcoma, ancillary testing has become increasingly important in making a definitive diagnosis, as more and more recurrent genetic alterations are discovered and new entities are defined. We present three cases of primary round cell sarcomas of the lung that proved diagnostically challenging, describe the features and ancillary testing that led to the correct diagnoses, and discuss classic and evolving entities among sarcomas with round cell morphology.

Does PAX7 and NKX2.2 immunoreactivity in Ewing sarcoma have prognostic significance?

Ewing sarcoma (ES) is an aggressive neoplasm with variable morphology. It has no specific immunoprofile or molecular signature. Neither CD99, NKX2.2 nor PAX7 immunoreactivity alone is completely specific, although diagnostic specificity improves when combined. The purpose of the present study was to investigate the immunohistochemical (IHC) expression of PAX7 in a large series of genetically confirmed ES. Existing results for CD99 and NKX2.2 immunoexpression, morphological findings and molecular studies (fusion gene subtypes) were retrieved from a previous study. Survival analyses were performed in cases with available clinical follow-up. PAX7 was positive in 95.5% of ES with diffuse staining (> 50%) in all positive cases and moderate or strong intensity for most cases. Nineteen ES displayed both PAX7 and CD99 immunoreactivity but lacked NKX2.2 immunoexpression. No relationships could be found between PAX7 expression and the histological types or ES gene fusion subtypes. Univariant/multivariate analysis showed that lack of PAX7 and/or NKX2.2 immunoexpression constitute independent poor prognostic factors for progression free survival (PFS) and overall survival (OS). In conclusion, IHC for CD99, NKX2.2, and PAX7 may be useful in daily practice for ES diagnosis, particularly in hospitals lacking facilities for molecular studies. In addition, the combination of strong CD99 membranous positivity and nuclear PAX7 and NKX2.2 immunoreactivity seems to be very reliable for ES diagnosis when supported by a corroborating histomorphologic and clinical picture. Although PAX7 is not entirely specific for ES, it seems to have a more extensive and strong nuclear immunoreactivity than NKX2.2 expression, even in tumors with decalcification artifact. Considering the prognostically significant data herein reported, we strongly recommend validation in prospective ES series that include localized and disseminated tumors.

Solid pancreatic masses in children: A review of current evidence and clinical challenges

Pancreatic tumors in children are infrequently encountered in clinical practice. Their non-specific clinical presentation and overlapping imaging characteristics often make an accurate preoperative diagnosis difficult. Tumors are categorized as epithelial or non-epithelial, with epithelial tumors further classified as tumors of the exocrine or endocrine pancreas. Although both are tumors of the exocrine pancreas, solid pseudopapillary neoplasm is the most prevalent solid pancreatic tumor in children, while pancreatoblastoma is the most common malignant tumor. Insulinoma is the most common pediatric pancreatic tumor of the endocrine pancreas. Malignant tumors require a complete, often radical, surgical resection. However, pancreatic parenchyma-sparing surgical procedures are utilized for benign tumors and low-grade malignancy to preserve gland function. This review will discuss the epidemiology, pathophysiology, clinical and diagnostic characteristics, and management options associated with both common and rare solid pancreatic masses in children. We will also discuss current challenges encountered in their evaluation and treatment.

WHO classification of soft tissue tumours 2020: An update and simplified approach for radiologists

The WHO classification of soft tissue tumours categorizes the lesions based on histological differentiation. In the recent fifth edition (2020), many new entities have been introduced, based on their distinct biological behaviour, genetics and morphology. With the recent advances and better understanding of molecular genetics, several novel recurrent genetic alterations have been incorporated in this edition. These may serve as reliable diagnostic and prognostic markers for various soft tissue tumours. Though predominantly a pathologist's game; the radiologists must be aware of the recent updates to contribute towards the optimal diagnosis and management of soft tissue tumours. The imaging features of the new entities have not yet been described but are expected to be explored in the coming years. We hereby present a concise review of the updates in the recent WHO classification of soft tissue tumours. We have tried to emphasize the novel molecular genetics and their surrogate immunohistochemical markers which have brought a paradigm shift in the diagnosis, therapeutics, and prognosis of soft tissue tumours. We also present simplified diagnostic algorithms to characterize soft tissue tumours based on the clinico-radiological features.

Ewing sarcoma: investigational mono- and combination therapies in clinical trials

INTRODUCTION

Over the last decades, multi-institutional clinical trials have resulted in significant improvements in the outcomes of patients with localized Ewing sarcoma; however, those with metastatic and recurrent diseases continue to fare poorly. More recently, advancements made in understanding the biology of the disease and mechanisms of response to therapy have opened the door for the incorporation of targeted therapies. Here we review the current state of treatment for Ewing sarcoma and the most recent preclinical advancements that have the potential to translate to improved care.

AREAS COVERED

This review provides a general overview of the most recent clinical trials completed in Ewing sarcoma, as well as the preclinical and translational data that has the potential to be incorporated into clinical trials. A PubMed review as well as a review of published meeting abstracts was used to compose this review.

EXPERT OPINION

While dose-intenstifying strategies have failed to lead to improvements in outcomes for patients with the highest-risk disease, recent preclinical advancements have shed light on potential new targeted strategies. The lack of early-phase clinical trial responses should not deter us from further developing these agents, but instead should guide us in designing novel combination strategies.

Adamantinoma-like Variant of Ewing Sarcoma in the Metatarsal Bone After Chemotherapy: Report of a Case Successfully Treated with Pedicled Osteocutaneous Fibular Transfer

Adamantinoma-like Ewing sarcoma is a rare variant of Ewing sarcoma with histologic and immunohistochemical evidence of squamous differentiation. This variant most commonly occurs in the head and neck region with a few cases reported in the long bones of the limbs. It may be associated with poorer clinical outcome and could pose a diagnostic challenge, particularly if it occurs in older patients or as a metastatic lesion. We present a case of Ewing sarcoma in the metatarsal of an 11-year-old boy that manifested adamantinoma-like morphology after neoadjuvant chemotherapy. Chemotherapy has been reported to induce neuronal maturation and rhabdoid morphology in cases of Ewing sarcoma, but no reports of treatment-induced squamous differentiation with P40/P63 expression have been demonstrated. This is also the first documented case treated with a pedicled osteocutaneous fibular transfer in a metatarsal malignancy, which is usually treated by either ray or below-knee amputation.

The 2020 WHO Classification: What's New in Soft Tissue Tumor Pathology?

The fifth edition of the World Health Organization Classification of Tumors of Soft Tissue and Bone was published in early 2020. The revisions reflect a consensus among an international expert editorial board composed of soft tissue and bone pathologists, geneticists, a medical oncologist, surgeon, and radiologist. The changes in the soft tissue tumor chapter notably include diverse, recently described tumor types (eg, atypical spindle cell/pleomorphic lipomatous tumor, angiofibroma of soft tissue, and CIC-rearranged sarcoma), new clinically significant prognostic information for a variety of existing entities (eg, dedifferentiated liposarcoma and solitary fibrous tumor), and a plethora of novel genetic alterations, some of practical diagnostic relevance (eg, NAB2-STAT6 in solitary fibrous tumor, FOSB rearrangements in epithelioid hemangioma and pseudomyogenic hemangioendothelioma, and SUZ12 or EED mutations in malignant peripheral nerve sheath tumor, leading to loss of H3K27 trimethylation). In this review, we highlight the major changes to the soft tissue chapter in the 2020 World Health Organization Classification, as well as the new chapter on undifferentiated small round cell sarcomas, with a focus on updates in diagnostic categories, prognostication, and novel markers. Recent discoveries in molecular genetics are also discussed, particularly those of immediate utility in differential diagnosis, including protein correlates detectable using immunohistochemistry.

Diagnostic Utility of a Custom 34-Gene Anchored Multiplex PCR-Based Next-Generation Sequencing Fusion Panel for the Diagnosis of Bone and Soft Tissue Neoplasms With Identification of Novel USP6 Fusion Partners in Aneurysmal Bone Cysts

CONTEXT.—

Bone and soft tissue tumors are heterogeneous, diagnostically challenging, and often defined by gene fusions.

OBJECTIVE.—

To present our experience using a custom 34-gene targeted sequencing fusion panel.

DESIGN.—

Total nucleic acid extracted from formalin-fixed, paraffin-embedded (FFPE) tumor specimens was subjected to open-ended, nested anchored multiplex polymerase chain reaction and enrichment of 34 gene targets, thus enabling detection of known and novel fusion partners.

RESULTS.—

During a 12-month period, 147 patients were tested as part of routine clinical care. Tumor percentage ranged from 10% to 100% and turnaround time ranged from 3 to 15 (median, 7.9) days. The most common diagnostic groups were small round blue cell tumors, tumors of uncertain differentiation, fibroblastic/myofibroblastic tumors, and adipocytic tumors. In-frame fusion transcripts were identified in 64 of 142 cases sequenced (45%): in 62 cases, the detection of a disease-defining fusion confirmed the morphologic impression; in 2 cases, a germline TFG-GPR128 polymorphic fusion variant was detected. Several genes in the panel partnered with multiple fusion partners specific for different diagnoses, for example, EWSR1, NR4A3, FUS, NCOA2, and TFE3. Interesting examples are presented to highlight how fusion detection or lack thereof was instrumental in establishing accurate diagnoses. Novel fusion partners were detected for 2 cases of solid aneurysmal bone cysts (PTBP1-USP6, SLC38A2-USP6).

CONCLUSIONS.—

Multiplex detection of fusions in total nucleic acid purified from FFPE specimens facilitates diagnosis of bone and soft tissue tumors. This technology is particularly useful for morphologically challenging entities and in the absence of prior knowledge of fusion partners, and has the potential to discover novel fusion partners.

The clinical prognostic factors and treatment outcomes of adult patients with Ewing sarcoma

BACKGROUND

The data about treatment results of Ewing sarcoma in adult patients are limited. The aim of our study was to analyze prognostic factors and outcomes of therapy in this group of patients.

METHODS

Between 2000 and 2018, 180 patients at the age of > 18 years old diagnosed with Ewing sarcoma were treated in referral center according to multimodal protocols. In 50 patients (28%) treatment was initiated outside our hospital, and 23 of them had started recommended therapy after 3 months since the date of biopsy/unscheduled operation. We analyzed clinical prognostic factors and overall survival (OS).

RESULTS

The median age was 28 years (18-67 years), primary tumor was localized axially in 114 patients (63%), metastases at presentation were detected in 51 pts (28%). 5-year OS rate was 65% for patients with localized disease, in metastatic disease it was 15%; the presence and the number of metastases was a prognostic factor. 5-year PFS was significantly better in patients treated at referral center (or when the patients were admitted to referral center within 3 months from the date of biopsy, which was performed outside referral center), comparing to patients treated initially outside referral center; 5-year PFS rates in total population were 28 and 13%, respectively. In terms of OS, unfavorable prognostic factor showing a statistical trend (p = 0.098) was lower dose density of neoadjuvant chemotherapy due to toxicity.

CONCLUSIONS

Approximately two-third of adult patients with localized Ewing sarcoma survive 5 years. In order to improve survival of this patients the multidisciplinary treatment in referral center is mandatory.

Clarifying prognostic factors of small cell osteosarcoma: A pooled analysis of 20 cases and the literature

Introduction

Small cell osteosarcoma (SCOS) is a rare subtype of osteosarcoma, with limited studies mainly focusing on histological features. Our study aims to analyze our own patients and those reported in the literature to increase the recognition of this rare disease, to evaluate patient survival and to further determine potential prognostic factors.

Material and methods

Twenty patients with SCOS were treated in our hospital between 2010 and 2019. Their follow-up data were collected retrospectively. A total of 336 literature cases from 58 manuscripts were retrieved by means of a PubMed search with the key word “small cell osteosarcoma”. Data pertaining to treatment and follow-up were extracted. We performed a pooled analysis for the survival of patients and the risk factors for local recurrence (LR), as well as metastatic disease (MD), in a total of 160 patients using the Kaplan-Meier method and Cox regression method.

Results

We reported our experience in diagnosing and treating SCOS. In our cases, elevated alkaline phosphatase (P = 0.013) and lactate dehydrogenase (P = 0.001) significantly impaired overall survival. In the pooled analysis, SCOS was diagnosed at the median age of 17 years and affected both sexes almost equally. The median follow-up duration was 19.5 months. In the pooled analysis cases, the 5-year overall survival rate was 38.6%, and 36.4% of patients survived 10 years. However, an increasing trend was detected, indicating recent improvements in management. The surgical margin status (P = 0.024) and metastases (P = 0.008) significantly impaired overall survival, and the response to chemotherapy was related to disease-free survival (P = 0.012). LR and MD were significantly correlated (P = 0.002) and could be observed after 5 years of follow-up. LR was significantly dependent on response to chemotherapy (P = 0.020). The development of MD seemed to be affected by response to chemotherapy (P = 0.060). Correlations between imaging features and prognosis were not detected.

Conclusions

This study suggested that positive margins, poor response to chemotherapy and MD are negative prognostic factors for SCOS, implied the potential role of laboratory examinations in the survival prediction and supported the need for prolonged or more intensive surveillance in patients with MD or LR. More well-documented literatures are encouraged to allow further confirmations.

Primary pancreatic Ewing sarcoma: a cytomorphologic and histopathologic study of 13 cases

INTRODUCTION

Ewing sarcoma (ES) is a small, round cell sarcoma that rarely occurs in solid organs, including the pancreas. A diagnostic overlap exists with other primary pancreatic neoplasms, especially for specimens from small biopsies and fine needle aspiration (FNA). To improve the diagnosis of this rare pancreatic tumor, we have reported a series of 13 cases of primary pancreatic ES and reviewed the cytopathologic, surgical pathology, clinical, and radiologic features of these neoplasms.

MATERIALS AND METHODS

We performed a retrospective case review of 13 patients with a diagnosis of pancreatic ES from 2 tertiary academic medical centers. A combination of cytology and histopathologic slides were reviewed, and the patient demographics, clinical information, somatic genetics, and radiologic findings were obtained from the electronic medical records.

RESULTS

Five FNA specimens from 5 patients and 8 surgical biopsy or resection specimens were identified and reviewed. The patients included 9 males and 4 females, with a median age of 27 years (range, 15-78 years). The cytology smears were highly cellular and showed a combination of complex tissue fragments and singly dispersed small round blue cells. The final diagnosis was ES for all 5 FNA specimens in accordance with the characteristic cytomorphology, diffuse and/or strong membranous immunolabeling for CD99, membranous β-catenin, and molecular confirmation of EWSR1 using fluorescence in situ hybridization or reverse transcriptase polymerase chain reaction.

CONCLUSIONS

The cytologic diagnosis of ES is challenging, especially in unusual locations such as the pancreas. However, the correct cytologic diagnosis is important because these patients will require neoadjuvant therapy before surgery. Confirmatory molecular studies should be required to render the diagnosis of pancreatic ES.

DNA Methylation Profiling for Diagnosing Undifferentiated Sarcoma with Capicua Transcriptional Receptor (CIC) Alterations

Undifferentiated soft tissue sarcomas are a group of diagnostically challenging tumors in the pediatric population. Molecular techniques are instrumental for the categorization and differential diagnosis of these tumors. A subgroup of recently identified soft tissue sarcomas with undifferentiated round cell morphology was characterized by Capicua transcriptional receptor (CIC) rearrangements. Recently, an array-based DNA methylation analysis of undifferentiated tumors with small blue round cell histology was shown to provide a highly robust and reproducible approach for precisely classifying this diagnostically challenging group of tumors. We describe the case of an undifferentiated sarcoma of the abdominal wall in a 12-year-old girl. The patient presented with a voluminous mass of the abdominal wall, and multiple micro-nodules in the right lung. The tumor was unclassifiable with current immunohistochemical and molecular approaches. However, DNA methylation profiling allowed us to classify this neoplasia as small blue round cell tumor with CIC alterations. The patient was treated with neoadjuvant chemotherapy followed by complete surgical resection and adjuvant chemotherapy. After 22 months, the patient is disease-free and in good clinical condition. To put our experience in context, we conducted a literature review, analyzing current knowledge and state-of-the-art diagnosis, prognosis, and clinical management of CIC rearranged sarcomas. Our findings further support the use of DNA methylation profiling as an important tool to improve diagnosis of non-Ewing small round cell tumors.