NKX2.2 is a Useful Immunohistochemical Marker for Ewing Sarcoma

Extraskeletal Ewing Sarcoma of the Gastrointestinal and Hepatobiliary Tract: Deceptive Immunophenotype Commonly Leads to Misdiagnosis

Ewing sarcoma (ES) is an uncommon mesenchymal neoplasm that typically develops as a bone mass, although up to 30% arise in extraskeletal sites. ES of the gastrointestinal (GI) and hepatobiliary tract is rare and may be misdiagnosed as other, more common neoplasms that occur in these sites. However, the correct classification of extraskeletal ES is important for timely clinical management and prognostication. We reviewed our experience of ES in the GI and hepatobiliary tract in order to further highlight the clinicopathologic features of these neoplasms and document the potential for misdiagnosis in this setting. The archives and consultation files of 6 academic institutions were retrospectively queried for cases of ES occurring in the GI and hepatobiliary tract. The histologic slides and ancillary studies were reviewed and clinical data were retrieved for each case through the electronic medical records, when available. Twenty-three patients with ES in the GI and/or hepatobiliary tract were identified from 2000 to 2022. Of these, 11 were women and 12 were men with a median age of 38 years (range, 2 to 64). Tumor locations included the pancreas (n=5), liver (n=2), stomach (n=3), colorectum (n=3), and small intestine (n=5), as well as tumors involving multiple organs, pelvis and retroperitoneum (n=5). Tumor size varied between 2 cm and 18 cm. Twenty were primary and 3 were metastases. Of the 23 cases, only 17% were initially diagnosed as ES. The most common misdiagnoses involved various forms of neuroendocrine neoplasia due to expression of synaptophysin and other neuroendocrine markers (22%). A wide variety of diagnoses including GI stromal tumor was considered due to aberrant CD117 expression (4%). The diagnosis of ES was ultimately confirmed by detection of the EWSR1 rearrangement in 22 cases. The remaining case was diagnosed using traditional immunohistochemistry. Follow-up information was available in 20 cases, with follow-up time varying between 2 and 256 months. Six patients with follow-up died of disease between 6 and 60 months following initial presentation. Our data indicate ES in the GI and hepatobiliary tract is commonly misdiagnosed leading to a delay in therapy. In light of the attendant therapeutic and prognostic implications, ES should be considered in the differential diagnosis of any GI or hepatobiliary tumor with epithelioid and/or small round cell morphology.

Beyond Bones: Exploring Primitive Neuroectodermal Tumor of Kidney

A primitive neuroectodermal tumor (PNET), classified as a malignancy of the Ewing's sarcoma family of tumors, is typically observed in bones or soft tissue among adolescents and young adults. However, its occurrence outside the skeletal system (extra-osseous location), particularly within visceral organs, is infrequent. Renal PNET is exceptionally uncommon and exhibits an exceedingly aggressive biological behavior, leading to a dismal prognosis as compared to conventional renal cell carcinoma. In this report, we present the case of a 28-year-old adult male patient diagnosed with renal PNET on ultrasound-guided biopsy, who initially presented with left flank pain and recent onset of hematuria within a brief timeframe. Left radical nephrectomy followed by postoperative VDC-IE (combined vincristine, doxorubicin, and cyclophosphamide followed by another combination of ifosfamide and etoposide) chemotherapy was given to the patient. This case serves as a reminder to nephrologists, medical oncologists, and pathologists that in adolescents and young adults presenting with suspicious renal masses, a diagnosis of renal PNET should always be considered. Timely surgical intervention, coupled with chemotherapy, is essential for optimal therapeutic management and improved prognosis in cases of such rare and aggressive malignancies.

Primary endobronchial multifocal Ewing's sarcoma: a rare case report

Extraskeletal Ewing's sarcoma (ES) has been reported to originate from various sites. Primary endobronchial ES is an extremely rare bronchial tumor, especially multifocal lesions. This report describes a rare presentation of primary bronchial ES in a 31-year-old female who was referred to the emergency department of our hospital due to suspicion of a foreign body in the bronchus. Computed tomography and bronchoscopy revealed multiple polypoid nodules in the middle bronchus of her right lung, thus excluding the initial diagnosis. Infection-related laboratory tests and serum tumor markers were normal. The bronchial sleeve resection was performed to remove the tumor completely and the patient's clinical symptoms obviously improved. Subsequent imaging, histopathological, immunohistochemical and genetic analyses made a conclusive diagnosis of primary endobronchial ES. To our knowledge, this is the eighth case of primary bronchial ES reported in medical literature.

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.

Extraosseous Ewing Sarcoma With Upper Gastrointestinal Bleeding

Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) is a type of malignancy that usually appears as a tumor in the bone. However, in a few patients with ES/PNET, it can occur outside of the bone. Although extraosseous ES/PNET can appear in various parts of the body, involvement of small bowel is rare. If it does, it can present with vague abdominal pain and gastrointestinal bleeding. This case report presents a 28-year-old gentleman with extraosseous ES/PNET in the duodenum who experienced gastrointestinal bleeding as a presenting symptom.

Evaluation of EWSR1/FUS rearrangements by FISH and NKX2.2 immunoexpression in simple bone cysts of the jaw

OBJECTIVE

Recent studies have identified recurrent rearrangements of EWSR1 or FUS with NFATC2 in extragnathic simple bone cysts (SBCs). We investigated the presence of EWSR1 or FUS rearrangements and the immunophenotypic expression of NKX2.2 and CD99 in a series of SBCs of the jaw.

STUDY DESIGN

We retrieved 10 cases of SBC of the jaw from the University of Pittsburgh archives. Of the 10 cases, we were able to evaluate 8 by immunohistochemistry for CD99 and NKX2.2 and 7 by fluorescence in situ hybridization (FISH) for EWSR1 and FUS rearrangement using EWSR1 and FUS break-apart probes.

RESULTS

All 8 cases evaluated by immunohistochemistry expressed CD99 but were negative for NKX2.2, and all 7 cases assayed using FISH were negative for EWSR1 and FUS rearrangements.

CONCLUSIONS

In contrast to the SBC of extragnathic sites, we found no presence of EWSR1 and FUS rearrangements by FISH in the SBC of the jaw, suggesting that this entity may be etiologically/molecularly distinct and reflects a non-neoplastic reactive process. However, as these lesions tend to be paucicellular, FISH may not be the appropriate technique for identifying EWSR1/FUS fusions. Other techniques should be used to evaluate them in future 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.

Primary Ewing sarcoma of the kidney: a rare entity with diagnostic challenges

Ewing sarcoma is a very rare tumour with aggressive behaviour and a poor prognosis. It tends to metastasize rapidly. Renal Ewing sarcoma is extremely rare, and only 48 cases have been reported in the literature. Herein, we report the case of a 14-year-old female presenting with a painful left flank swelling. Ultrasound and magnetic resonance imaging showed a large tumour invading the left kidney, heterogeneously enhanced after injection, associated with lymph nodes and peritoneal carcinomatosis. A thoraco-abdomino-pelvic computed tomography scan revealed pulmonary nodules and osteolytic lesions. A biopsy was performed, and histology, immunohistochemistry, and molecular studies confirmed the diagnosis of retroperitoneal Ewing sarcoma. Multi-agent chemotherapy followed by radical nephrectomy was performed, confirming the renal origin, and histology showed a post-therapeutical response. After a 1-year follow-up, there was no evidence of recurrence. We report this case to highlight the rarity of this entity and its challenging clinico-pathological diagnosis when presenting as a renal tumour.

The value of GLI1 and p16 immunohistochemistry in the premolecular screening for GLI1-altered mesenchymal neoplasms

Mesenchymal neoplasms with GLI1 alterations have recently been reported in several anatomic locations. Their morphology and immunohistochemistry (IHC) are nonspecific, making their recognition a true challenge. To assess the diagnostic value of GLI1 and p16 IHC for identifying GLI1-altered neoplasms, we evaluated 12 such neoplasms (6 GLI1-amplified and 6 with GLI1-fusions) using the GLI1 IHC. Additionally, we evaluated some of their morphological and molecular mimickers, including glomangiomas, Ewing sarcomas (ES), myxoid liposarcomas, and MDM2/CDK4-amplified sarcomas (well-differentiated liposarcoma/WDLPS, dedifferentiated liposarcoma/DDLPS, and intimal sarcoma). All successfully tested GLI1-altered tumors (11/11) demonstrated at least moderate/strong nuclear and/or cytoplasmic GLI1 IHC positivity. GLI1-amplified tumors exhibited a moderate/strong predominantly nuclear staining, compared to a moderate, patchy, and predominantly cytoplasmic GLI1 positivity in GLI1-fusion tumors. Among their mimics, GLI1 immunoreactivity, either cytoplasmic or nuclear, was observed in intimal sarcoma (3/3) and WDLPS/DDLPS (22/25). GLI1 IHC demonstrated 92% sensitivity and 90.8% specificity in diagnosing GLI1-altered neoplasms. Strong/moderate nuclear/cytoplasmic p16 immunoexpression was noted in all GLI1-amplified tumors compared to none of fused cases. Overall, the GLI1/p16 combination demonstrated a sensitivity and specificity of 100% and 93% for GLI1-amplified tumors. In conclusion, we confirm that GLI1 IHC represents a good, quick, and cheap helpful screening tool. The inclusion of p16 may aid in pre-screening for potential GLI1-amplified neoplasms and provide insights on which tumors warrant further molecular testing.

Updates on WHO classification for small round cell tumors: Ewing sarcoma vs. everything else

The WHO Classification of Soft Tissue and Bone Tumours currently recognizes four categories of undifferentiated small round cell sarcoma: Ewing sarcoma, round cell sarcoma with EWSR1-non-ETS fusions including NFATc2 and PATZ1, CIC-rearranged sarcoma, and sarcoma with BCOR genetic alterations. These neoplasms frequently pose significant diagnostic challenges due to rarity and overlapping morphologic and immunohistochemical findings. Further, molecular testing, with accompanying pitfalls, may be needed to establish a definitive diagnosis. This review summarizes the clinical, histologic, immunohistochemical, and molecular features of these neoplasms. In addition, differential diagnosis and areas of uncertainty and ongoing investigation are discussed.

Beyond cyclopamine: Targeting Hedgehog signaling for cancer intervention

Hedgehog (Hh) signaling plays a significant role in embryogenesis and several physiological processes, such as wound healing and organ homeostasis. In a pathological setting, it is associated with oncogenesis and is responsible for disease progression and poor clinical outcomes. Hedgehog signaling mediates downstream actions via Glioma Associated Oncogene Homolog (GLI) transcription factors. Inhibiting Hh signaling is an important oncological strategy in which inhibitors of the ligands SMO or GLI have been looked at. This review briefly narrates the Hh ligands, signal transduction, the target genes involved and comprehensively describes the numerous inhibitors that have been evaluated for use in various neoplastic settings.

Ewing Sarcoma of the Vagina: A Rare Clinical Entity

Ewing sarcoma (EwS), a malignancy primarily affecting adolescents and young adults, encompasses various types such as bone, extraskeletal, chest wall, and soft tissue-based tumors, all of which share a common genetic origin. A small portion of them are extraosseous, impacting diverse anatomical sites. Characterized by a specific translocation, this rare cancer rarely involves the vagina, with very few documented cases. This report details the unique case of a middle-aged woman diagnosed with extraosseous vaginal EwS, a rarity in this age group and gender. With no established guidelines, a multidisciplinary approach is crucial, emphasizing the need for further case reporting to enhance understanding and management strategies.

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.

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.

Expression of NKX2.2 in Non-Ewing Tumors With Round Cell Morphology

Background Round cell sarcomas pose diagnostic challenges due to overlapping histopathological features, necessitating precise immunohistochemical markers for accurate categorization. NKX2.2 has emerged as a sensitive diagnostic tool, particularly in Ewing sarcoma. This study extends this understanding to various round-cell sarcomas, shedding light on the potential diagnostic utility of NKX2.2 beyond its established role. The nuanced exploration of NKX2.2 expression aims to enhance diagnostic strategies, prognostic assessments, and therapeutic developments in the landscape of sarcoma research. Methodology Cases were retrieved from the surgical pathology and consultation files of Shaukat Khanum Memorial Cancer Hospital and Research Center, Lahore, Pakistan. Representative hematoxylin and eosin-stained slides of six different types of already confirmed tumors, including lymphoblastic lymphoma, neuroblastoma, rhabdomyosarcoma, synovial sarcoma, Wilms tumor, and Ewing sarcoma, were reviewed by a panel of pathologists. Immunohistochemistry, utilizing a rabbit anti-NKX2.2 monoclonal antibody, was performed on formalin-fixed paraffin-embedded tissue sections. The presence of NKX2.2 was defined as moderate or high nuclear immunoreactivity in at least 5% of cells. Results The histopathological examination revealed characteristic features in each sarcoma subtype, aligning with established diagnostic criteria. In Lymphoblastic lymphoma, T-cell lineage was confirmed through TdT expression, while the atypical finding of focal NKX 2.2 expression hinted at genetic diversity. Neuroblastoma exhibited the expected salt and pepper chromatin pattern, with NKX 2.2 expression raising questions about its prognostic significance. Rhabdomyosarcoma presented primitive cells expressing desmin, and NKX 2.2 focal expression echoed previous subtype-associated studies. Synovial sarcoma displayed both monophasic and biphasic growth patterns and TLE1 expression, with NKX 2.2 variation suggesting tumor heterogeneity. In Wilms tumor, the characteristic WT1 expression was observed, while NKX2.2's absence reaffirmed its irrelevance in this context. Ewing sarcoma displayed the anticipated homogenous cell population, strong NKX2.2 expression, and CD99 positivity across various sites. Furthermore, age and gender impact on this range of sarcomas found no significant relation with an expression of NKX2.2. Conclusion In conclusion, the diverse expression profiles of diagnostic markers discovered in this study, particularly the atypical expression of NKX2.2 beyond its established role in Ewing sarcoma, signify a significant advancement. This unique finding accentuates the potential diagnostic importance of NKX2.2 in various sarcomas, presenting a novel dimension to our understanding of these malignancies.

Ewing's Sarcoma of the Hand: An Unusual Presentation in a Young Hispanic Male

Ewing's sarcoma is a neuroectodermal malignancy classically associated with innocuous and chronic symptomatology. Although tumors typically involve the axial skeleton, some malignancies may be confined to extraosseous tissue only. This report presents the case of a 15-year-old Hispanic male with a tender, slow-growing mass of seven months in the subcutaneous tissue of the right hand. Core needle biopsy and fine needle aspiration confirmed the diagnosis of high-grade extraosseous Ewing's sarcoma and the patient was treated via surgical resection and chemotherapy. Nonspecific findings of Ewing's sarcoma may mimic infection or trauma and contribute to a delay in diagnosis. However, social and economic influences including limited English proficiency and insurance status also critically affect the timing of presentation.

CRISPR-Cas9 knockout screening identifies KIAA1429 as an essential gene in Ewing sarcoma

BACKGROUND

Ewing sarcoma (ES) is an aggressive childhood bone and soft tissue cancer. KIAA1429 is one type of N6-methyladenosine (m6A) writer that plays a tumor-progressive role in various cancers, but the role of KIAA1429 in ES remains to be elucidated. The aim of the study was to investigate the role of KIAA1429 in ES.

METHODS

We performed a multi-omic screen including CRISPR-Cas9 functional genomic and transcriptomic approaches, and identified that KIAA1429 played a significant role in ES progression. Gene knockdown, quantitative real-time PCR (Q-RT-PCR), immunoblotting, CellTiter-Glo assays, clonogenic assays, a subcutaneous xenograft model and immunohistochemistry were used to assess the functional role of KIAA1429 in ES. We mainly conducted RNA sequencing (RNA-seq) in ES cells to analyze the downstream regulatory mechanism of KIAA1429. An integrative analysis of chromatin immunoprecipitation sequencing (ChIP-seq) and RNA-seq indicated the upstream regulatory mechanism of KIAA1429.

RESULTS

In vitro and in vivo CRISPR-Cas9 knockout screening identified KIAA1429 as an ES-dependent gene. Genetic suppression of KIAA1429 inhibited ES cell proliferation and tumorigenicity both in vitro and in vivo. Further studies revealed that KIAA1429 promotes ES tumorigenesis by regulating the ribosome-associated cell cycle and cancer-related inflammation. Interestingly, we found that STAT3 was a target of KIAA1429 and that a STAT3 inhibitor reduced KIAA1429 transcript levels, indicating positive feedback between KIAA1429 and STAT3. Finally, we found that NKX2-2 bound to the KIAA1429 promoter and transactivated KIAA1429.

CONCLUSION

Our study systematically analyzed ES-dependent epigenetic/transcriptional regulatory genes and identified KIAA1429 as a biomarker of tumor progression in ES, providing a potential therapeutic target for treating ES.

NK2 homeobox gene cluster: Functions and roles in human diseases

NK2 genes (NKX2 gene cluster in humans) encode for homeodomain-containing transcription factors that are conserved along the phylogeny. According to the most detailed classifications, vertebrate NKX2 genes are classified into two distinct families, NK2.1 and NK2.2. The former is constituted by NKX2-1 and NKX2-4 genes, which are homologous to the Drosophila scro gene; the latter includes NKX2-2 and NKX2-8 genes, which are homologous to the Drosophila vnd gene. Conservation of these genes is not only related to molecular structure and expression, but also to biological functions. In Drosophila and vertebrates, NK2 genes share roles in the development of ventral regions of the central nervous system. In vertebrates, NKX2 genes have a relevant role in the development of several other organs such as the thyroid, lung, and pancreas. Loss-of-function mutations in NKX2-1 and NKX2-2 are the monogenic cause of the brain-lung-thyroid syndrome and neonatal diabetes, respectively. Alterations in NKX2-4 and NKX2-8 genes may play a role in multifactorial diseases, autism spectrum disorder, and neural tube defects, respectively. NKX2-1, NKX2-2, and NKX2-8 are expressed in various cancer types as either oncogenes or tumor suppressor genes. Several data indicate that evaluation of their expression in tumors has diagnostic and/or prognostic value.

Molecular and biologic biomarkers of Ewing sarcoma: A systematic review

With an annual incidence of less than 1%, Ewing sarcoma mainly occurs in children and young adults. It is not a frequent tumor but is the second most common bone malignancy in children. It has a 5-year survival rate of 65-75%; however, it has a poor prognosis when it relapses in patients. A genomic profile of this tumor can potentially help identify poor prognosis patients earlier and guide their treatment. A systematic review of the articles concerning genetic biomarkers in Ewing sarcoma was conducted using the Google Scholar, Cochrane, and PubMed database. There were 71 articles discovered. Numerous diagnostic, prognostic, and predictive biomarkers were found. However, more research is necessary to confirm the role of some of the mentioned biomarkers. .

Clinicopathological features of five cases of CIC::DUX4 positive sarcomas, including literature review

According to the recent World Health Organization (WHO) classification, CIC-rearranged sarcomas, including CIC::DUX4-positive sarcomas constitute an aggressive subtype of undifferentiated round cell sarcomas. There is a single study on these tumors from our subcontinent. We present clinicopathological features of 5 additional cases of this tumor entity, including literature review. Thirty-nine undifferentiated round cell sarcomas, excluding Ewing sarcomas (ES), were tested for CIC::DUX4 fusion, including Type I (165 base pair size) and II (230 bp) by reverse transcription-polymerase chain reaction. Twenty-five of those tumors were tested for EWSR1 gene rearrangement, 5 for SS18 and 4 for SS18::SSX fusion, and were negative for those tests. Five tumors (12.8 %) were positive for CIC::DUX4(Type II) fusion. Five CIC:: DUX4-positive sarcomas occurred in 4 males and one female; of 25-43 years of age, in soft tissues, including thigh (n = 2), chest wall (n = 1), iliac region (n = 1) and foot (n = 1). Tumor size varied from 2.2 to 19 cm. Microscopically, the tumors were predominantly composed of nodules and sheets of malignant round to epithelioid cells, including "rhabdoid-like" (n = 2) and spindle-shaped (n = 2) with eosinophilic to vacuolated cytoplasm (4/5), distinct nucleoli (4/5), brisk mitoses, focal myxoid to hyalinised stroma (4/5) and necrosis (5/5). Immunohistochemically, tumor cells were positive for WT1 (5/5), calretinin (3/4), pan-keratin (1/4), CD99/MIC2 ("dot-like" to cytoplasmic membranous) (4/4), while negative for desmin (0/4), S100P (0/4), and NKX2.2 (0/5). INI1/SMARCB1 was retained (3/3). All patients underwent excision with adjuvant radiotherapy and chemotherapy (Ewing sarcoma regimen). A single patient developed recurrence, and 2 developed pulmonary metastasis, including one with brain metastasis. CIC:: DUX4-positive sarcomas are ultra-rare tumors, that mainly occur in the soft tissues and in young adult patients. Histopathologically, these tumors display a wide spectrum, including round to epithelioid cells, variable amount of cytoplasmic vacuolization and myxoid stroma with necrosis. Immunohistochemically, these tumors express WT1 and calretinin. Despite adjuvant therapies, these tumors have dismal outcomes, especially in large-sized tumors. CIC::DUX4-positive sarcomas need to be differentiated from their histopathological mimics, including ES, in view of significant treatment-related implications.

CYP1A1 Is a Useful Diagnostic Marker for Angiofibroma of Soft Tissue

Angiofibroma of soft tissue (AFST) is a recently described benign fibroblastic neoplasm composed of uniform bland spindle cell proliferation in fibrous and fibromyxoid stroma with prominent thin-walled small branching vessels. A major recurrent genetic abnormality in AFST is t(5;8)(p15;q13), which results in the rearrangement of AHRR and NCOA2 . Owing to a lack of discriminatory IHC markers and potential overlap with other mesenchymal neoplasms, it may be difficult to confirm the diagnosis of AFST in some cases. Triggered by a recent gene expression profile study of AFST, which showed the significant upregulation of AhR/AHRR/ARNT downstream genes (including CYP1A1 ), we used a mouse monoclonal antibody to explore the diagnostic significance of CYP1A1 expression in histologically confirmed AFST cases along with 224 control cases, consisting of 221 neoplastic mimickers and 3 non-neoplastic lesions. We found moderate to strong cytoplasmic expression of CYP1A1 in 13 of 16 AFST cases (sensitivity, 81.3%). In contrast, the vast majority of other examined histologic mimickers exhibited no expression of CYP1A1 (specificity, 97.3%), except for 3 myxofibrosarcomas (3/31), 2 solitary fibrous tumors (2/22), and 2 neurofibroma (1/27). Our results indicate that CYP1A1 immunohistochemistry may aid in the diagnosis of AFST by distinguishing among various kinds of tumors, particularly those harboring prominent vasculature.

Validation of PRKCB Immunohistochemistry as a Biomarker for the Diagnosis of Ewing Sarcoma

Background: Ewing sarcoma (ES) can be confirmed by identifying the EWSR1-FLI1 fusion transcript. This study is to investigate whether immunostaining (IHC) of PRKCB-a protein directly regulated by EWSR1-FLI1 is a surrogate maker for diagnosing ES in routine practice. Methods: Microarray gene expression analyses were conducted. RKCB IHC was applied to 69 ES confirmed by morphology and molecular methods, and 41 non-Ewing small round cell tumors. EWSR1 rearrangement, EWSR1-FLI1 fusion or t(11;22)(q24;q12) were identified by fluorescence in situ hybridization, reverse transcriptase polymerase chain reaction, or cytogenetic analysis, respectively. Results: Gene array analyses showed significant overexpression of the PRKCB in ES. PRKCB IHC was positive in 19 cases of ES with EWSR1-FLI1 fusion, 3 cases with cytogenetic 11:22 translocation and 59 cases with EWSR1 rearrangement while negative in only one EWSR1 rearranged case. PRKCB IHC is sensitive (98%) and specific (96%) in detecting EWSR1 rearranged ES. Conclusions: PRKCB is a reliable antibody for diagnosing ES in routine practice.

Primary Cutaneous Ewing Sarcoma of the Scalp With Metastasis to the Lung: An Unusual Manifestation During Pregnancy

ABSTRACT

A 32-year-old G2P1L1 (5 months pregnant) woman presented with a 3-month history of a slow-growing cystic lesion on her scalp vertex. Similar lesions in the exact location were excised twice in the past with a diagnosis of trichilemmal carcinoma (TC). A biopsy of the scalp lesion showed morphology and immunoprofile consistent with previously diagnosed TC. Staging PET/CT demonstrated a 4.7 cm right upper lobe lung, and a subsequent lung biopsy showed a small, round blue-cell tumor with necrosis, morphologically identical to the prior biopsies from the scalp. Considering the unusual clinical course of TC, a lung biopsy was sent for next-generation sequencing that showed EWSR1-FLI1 (type1) fusion. Additionally, CD99 immunostaining revealed uniform cytoplasmic and membranous staining in the tumor cells. The previous scalp excision specimen was also sent for mutation analysis, which showed EWSR1-FLI1 fusion. In conjunction with clinical history and histological and molecular findings, a definitive diagnosis of primary cutaneous Ewing sarcoma (PCES) with local recurrence and metastasis to the lung was made. We present a case of PCES, which was previously misdiagnosed and treated as TC. This case emphasizes the importance of CD99 in the initial screening of cutaneous small round blue-cell tumors to avoid misdiagnosis from other morphological overlaps. Also, despite its rarity, PCES should be included in the differential diagnosis of small, round, blue cell tumors at cutaneous sites. Our case also exemplifies common biases in medical decision-making, including premature closure and anchoring bias which can result in misdiagnosis or diagnostic delay and associated delay in appropriate management.

Childhood sarcomas: fine-needle aspiration cytopathology with an emphasis on the use of molecular studies

INTRODUCTION

In children and adolescents, most sarcoma subtypes have a simple karyotype with a single genetic alteration; cytologic findings combined with ancillary testing can lead to a specific diagnosis. The goal of this study was to review the use of fine-needle aspiration in conjunction with immunohistochemistry and molecular studies as a part of an integrated, multidisciplinary diagnostic workup for bone and soft tissue sarcomas in this population.

MATERIALS AND METHODS

We searched for cases aged ≤18 years old with a malignant bone or soft tissue tumor that had corresponding cytology specimens from 3 institutions. Clinical data, cytologic findings and diagnoses, histologic diagnoses, and ancillary testing were documented.

RESULTS

Of 99 cases, 55% were male with a mean age of 12 years. Ninety-four cases (95%) had a specific histologic diagnosis, and 84 cases (85%) were primary neoplasms. Ninety-four cases (95%) had a malignant cytologic diagnosis, and 71 cases (72%) had a specific cytologic diagnosis concordant with the histologic diagnosis. Among primary tumors with a specific histologic diagnosis, a specific cytologic diagnosis was made in 63 cases (79%). After excluding osteosarcoma, 74% of the tumors (n = 50) had molecular studies. Specific genetic alterations supporting a definitive diagnosis were found in 42 cases (84%), the majority of which were demonstrated using Fluorescence In Situ Hybridization (n = 33, 79%).

CONCLUSIONS

We found that fine-needle aspiration in conjunction with core needle biopsy, immunohistochemistry, and molecular studies allowed cytopathologists to accurately classify sarcomas in a pediatric age group.

Ewing and Ewing-like sarcomas: A morphological guide through genetically-defined entities

The fifth edition of the World Health Organization classification of soft tissue and bone tumors redefined Ewing sarcoma by fusions between EWSR1/FUS and ETS family of transcription factors, and recognized three tumor groups among Ewing-like sarcoma: CIC-rearranged sarcoma, sarcoma with BCOR genetic alterations, and round cell sarcoma with EWSR1::non-ETS fusions. Although this classification underscores the critical role of molecular genetics in the diagnosis of small round cell sarcoma, each entry is recognized as a specific entity not only because they have different genetics but because their phenotypes are distinct and reasonably robust to support the diagnosis. This review focuses on the morphological aspects of Ewing sarcoma and a subset of Ewing-like sarcomas (CIC-rearranged sarcoma, BCOR-associated sarcoma, and EWSR1::NFATC2 sarcoma) for which phenotypic characteristics have been well established. Classic histological findings, uncommon variations, and recurrent diagnostic pitfalls are addressed, along with the utility of recently developed immunohistochemical markers (NKX2.2, PAX7, ETV4, BCOR, CCNB3, and NKX3.1). Phenotypic expertise would significantly expedite the diagnostic process and complement (or sometimes outperform) genetic testing, even in well-resourced settings. Morphological knowledge plays an even more substantial role in facilities that do not have easy access to molecular testing.

TrkC, a novel prognostic marker, induces and maintains cell survival and metastatic dissemination of Ewing sarcoma by inhibiting EWSR1-FLI1 degradation

Upregulation of EWSR1-FLI1 expression has been associated with invasiveness, induced cell survival, metastatic dissemination, and acquisition of self-renewal traits in Ewing sarcoma (ES). Although existing evidence implies that TrkC expression is linked to the pathogenesis of other cancer types, its role and the mechanism behind its correlation with EWSR1-FLI1 in the pathogenesis of ES remain unclear. In this study, we uncovered a novel physiological role of TrkC as a key regulator of EWSR1-FLI1 involved in the survival and metastatic dissemination of ES. TrkC was observed to be frequently overexpressed in human metastatic ES cells in vitro and in vivo, facilitating enhanced survival, tumorigenicity, and metastasis of ES cells. TrkC-mediated metastasis of ES cells was induced by the inhibition of the proteasomal degradation of EWSR1-FLI1 via the TrkC/EWSR1-FLI1 complex, which subsequently enabled the induction of the target proteins, EGR2 and NKX2.2. Moreover, TrkC significantly inhibited tumor suppressor activity of TGF-β through reduction of the mRNA expression of one of its receptors, TGFBR2 via TrkC-induced stabilization of EWSR1-FLI1. Furthermore, loss of TrkC expression inhibited tumor growth and metastasis in experimental mouse models. This study is the first to report the involvement and functional role of TrkC in the pathogenesis of ES, suggesting important implications for understanding the alterations of TrkC in Ewing tumors.

Ewing sarcoma of the ileum with wide multiorgan metastases: A case report and review of literature

BACKGROUND

Ewing sarcoma (ES) is an aggressive small round cell tumor that usually occurs in younger children and young adults but rarely in older patients. Its occurrence in elderly individuals is rare. ES of the ileum with wide multiorgan metastases is rarely reported and difficult to distinguish radiologically from other gastrointestinal tract tumors.

CASE SUMMARY

A 53-year-old man presented with right lower quadrant pain for 2 wk. Computed tomography results showed a heterogeneous mass within the ileum and widespread multiorgan metastases. This mass was biopsied, and pathological examination of the resected specimen revealed features consistent with an extraskeletal ES.

CONCLUSION

This case emphasizes the importance of recognizing this rare presentation in the small intestine to broaden the differential diagnosis of adult intraabdominal tumors.

Adamantinoma with a Prominent Spindle Cell Component Mimicking Intraosseous Synovial Sarcoma: Clinicopathological Features of Six Tumors

Introduction. Adamantinoma is sub-classified into classic/biphasic, osteofibrous dysplasia-like, and de-differentiated type. We present six adamantinomas with a prominent spindle cell component mimicking intraosseous synovial sarcomas. Methods. Six patients were either referred with a diagnosis of intraosseous synovial sarcoma or wherein synovial sarcoma was a differential diagnosis. Three tumors were tested for SS18 gene rearrangement by FISH and two for SS18::SSX fusion by RT-PCR technique. Results. There were three males and three females with an average age of 20.6 years. Radiologically, the lesions were expansile and showed lytic and/or sclerotic components, involving the cortex and/or medulla. Five lesions occurred in the tibia and two in the fibula. Two tumors displayed soft tissue extension and two occurred as multifocal lesions. Two patients were diagnosed with synovial sarcoma and a single patient with sarcomatoid carcinoma, elsewhere. Two "in-house" patients were initially diagnosed with synovial sarcomas. On review, all tumors were cellular comprising monomorphic spindle-shaped cells arranged in sheets and fascicles (n = 6), including a "herringbone-like" pattern (n = 3), focal tubules (n = 1), cohesive nests (n = 5), cords (n = 2), including pseudocystic component (n = 2). Immunohistochemically, tumor cells were positive for p63 (6/6), p40 (4/4), EMA (2/3), AE1/AE3 (5/6), various keratins (2/2), and TLE1 (2/4). Three tumors tested for SS18 rearrangement were negative, while two tumors tested for SS18::SSX fusion were negative. Conclusions. Adamantinomas with spindle cell morphology display overlapping features with synovial sarcoma. A clinico-radiological index of suspicion immunostains (p63 and p40) and molecular test for t(X; 18) translocation are useful in an exact diagnosis, which has treatment-related implications.

Prospective Clinical Genomic Profiling of Ewing Sarcoma: ERF and FGFR1 Mutations as Recurrent Secondary Alterations of Potential Biologic and Therapeutic Relevance

Ewing sarcoma (ES) is a primitive sarcoma defined by EWSR1-ETS fusions as the primary driver alteration. To better define the landscape of cooperating secondary genetic alterations in ES, we analyzed clinical genomic profiling data of 113 patients with ES, a cohort including more adult patients (> 18 years) and more patients with advanced stage at presentation than previous genomic cohorts.

Imaging Findings of Hepatic Ewing's Sarcoma on Computed Tomography and Gadobenate Dimeglumine-enhanced Magnetic Resonance Imaging: A Case Report and Literature Review

Ewing's sarcoma (ES) is a tumor that often occurs in the long bones and rarely arises from visceral organs primarily. Here, we report a case of primary hepatic ES, discuss its computed tomography (CT) and gadobenate dimeglumine-enhanced magnetic resonance (MRI) features. This is the first Chinese and fifth primary hepatic ES case reported, based on a literature review. Imaging examinations showed that the tumor was solid, with necrosis and hemorrhage. Contrast-enhanced images showed that the tumor was hypervascular and especially had heterogeneous signal intensity on hepatobiliary phase MRI images. Intratumoral vessels and vascular invasion were also present.

Oncofusion-driven de novo enhancer assembly promotes malignancy in Ewing sarcoma via aberrant expression of the stereociliary protein LOXHD1

Ewing sarcoma (EwS) is a highly aggressive tumor of bone and soft tissues that mostly affects children and adolescents. The pathognomonic oncofusion EWSR1::FLI1 transcription factor drives EwS by orchestrating an oncogenic transcription program through de novo enhancers. By integrative analysis of thousands of transcriptomes representing pan-cancer cell lines, primary cancers, metastasis, and normal tissues, we identify a 32-gene signature (ESS32 [Ewing Sarcoma Specific 32]) that stratifies EwS from pan-cancer. Among the ESS32, LOXHD1, encoding a stereociliary protein, is the most highly expressed gene through an alternative transcription start site. Deletion or silencing of EWSR1::FLI1 bound upstream de novo enhancer results in loss of the LOXHD1 short isoform, altering EWSR1::FLI1 and HIF1α pathway genes and resulting in decreased proliferation/invasion of EwS cells. These observations implicate LOXHD1 as a biomarker and a determinant of EwS metastasis and suggest new avenues for developing LOXHD1-targeted drugs or cellular therapies for this deadly disease.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Soft Tissue Tumors

The fifth (5th) edition of the World Health Organization (WHO) Classification of Head and Neck Tumors introduces a new chapter dedicated to soft tissue neoplasms commonly affecting the head and neck. While the diversity, rarity, and wide anatomic range of soft tissue tumors precludes a discussion of all entities that may be found in the head and neck, the addition of this new chapter to the head and neck "blue book" aims to provide a more comprehensive and uniform reference text, including updated diagnostic criteria, of mesenchymal tumor types frequently (or exclusively) arising at head and neck sites. Since publication of the previous edition in 2017, there have been numerous advances in our understanding of the pathogenesis of many soft tissue tumors which have facilitated refinements in tumor classification, identification of novel entities, development of diagnostic markers, and improved prognostication. This review will provide a focused discussion of the soft tissue tumors included in the 5th edition WHO Head and Neck classification, with an emphasis on updates.

Identification of novel SSX1 fusions in synovial sarcoma

Synovial sarcoma is characterized by variable epithelial differentiation and specific SS18-SSX gene fusions. The diagnosis is primarily based on phenotype, but fusion gene detection is increasingly being considered indispensable, with SS18 break-apart fluorescence in situ hybridization (FISH) being favored in many laboratories. However, SS18 FISH assay produces negative or atypical results in a minority of cases, leaving uncertainties in diagnosis and management. Here, we analyzed this challenging subset of SS18 FISH-negative/atypical synovial sarcoma using RNA sequencing and monoclonal antibodies that recognize SS18-SSX and the SSX C-terminus. Among 99 synovial sarcoma cases that were previously subjected to SS18 break-apart FISH, eight cases were reported as negative and three cases were indeterminate, owing to atypical signal patterns. Three of these 11 tumors (two monophasic and one biphasic) harbored novel EWSR1-SSX1 fusions, were negative for SS18-SSX staining, and were positive for SSX C-terminus staining. One monophasic tumor harbored a novel MN1-SSX1 fusion, and showed negative SS18-SSX expression and positive SSX C-terminus staining. Another monophasic tumor carried an SS18L1-SSX1 fusion, and was weakly positive for SS18-SSX, while SMARCB1 expression was reduced. The presence of these novel and/or rare fusions was confirmed using RT-PCR and Sanger sequencing. EWSR1-SSX1 was further validated by EWSR1 FISH assay. The remaining six tumors (five monophasic and one biphasic) showed strong SS18-SSX expression, and RNA sequencing successfully performed in three cases identified canonical SS18-SSX2 fusions. Based on a DNA methylation-based unsupervised clustering, the tumors with EWSR1-SSX1 and SS18L1-SSX1 clustered with synovial sarcoma, while the MN1-SSX1-positive tumor was not co-clustered despite classic histology and immunoprofile. In summary, we discovered novel and rare SSX1 fusions to non-SS18 genes in synovial sarcoma. The expanded genetic landscape carries significant diagnostic implications and advances our understanding of the oncogenic mechanism.

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.

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.

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.

Advances in the classification of round cell sarcomas

Round cell sarcomas represent a diagnostic challenge for pathologists, owing to the poorly differentiated features of these high-grade tumours. The diagnosis of round cell sarcoma requires large immunohistochemical panels and molecular testing in many cases. This spectrum of malignancies is largely dominated by Ewing sarcomas (ESs), which represent the most common family of these tumours. Nonetheless, new families have been delineated in the past few years, with the addition of two additional families in the 2020 World Health Organization classification of bone and soft tissue tumours, namely sarcomas with CIC rearrangements and sarcomas with BCOR alterations. EWSR1, one of the genes involved in the driver fusion of ESs, is also implicated in the translocation of many other tumours with heterogeneous lineages and variable levels of aggressiveness. Round cell sarcomas associated with fusions inwhichEWSR1is partnered with genes encoding transcription factors distinct from those of the 'Ewing family' represent a heterogeneous group of rare tumours that require further study to determine whether their fusions may or not define a specific subgroup. They include mainly sarcomas with NFATc2 rearrangements and sarcomas with PATZ1 rearrangements. At this point, PATZ1 fusions seem to be associated with tumours of high clinical and morphological heterogeneity. Molecular studies have also helped in the identification of more consistent biomarkers that give tremendous help to pathologists in triaging, if not diagnosing, these tumours in practice. This review compiles the latest accumulated evidence regarding round cell sarcomas, and discusses the areas that are still under investigation.

Osteosarcoma: Old and New Challenges

Diagnosis of osteosarcoma can be challenging because of its diverse histological patterns and the lack of diagnostic biomarkers for most examples. This review summarizes the key pathologic findings of osteosarcoma subtypes (high-grade central, parosteal, low-grade central, periosteal, high-grade surface, and secondary) with an emphasis on describing and illustrating histological heterogeneity to help general pathologists. Differential diagnoses are listed for each entity, and histological subtype and distinguishing features, including molecular genetic findings (eg, MDM2, IDH, H3F3A, FOS, and USP6), are discussed. The review also covers recently established and emerging concepts and controversies regarding osteosarcoma.

Undifferentiated Small Round Cell Sarcomas of Bone

Undifferentiated small round cell sarcomas represent a heterogeneous group of mesenchymal neoplasms. While imprecise, this term nevertheless provides a useful framework for conceptualizing these tumors. This article highlights current trends in their classification based on morphology, immunohistochemistry, and advanced molecular techniques. As next-generation sequencing becomes commonplace in diagnostic laboratories pathologists can expect to differentiate these tumors with increasing confidence, and actively contribute to related discoveries. Ultimately, when synthesized with rigorous clinical outcome data and other investigative techniques, a more robust landscape for the molecular diagnosis and classification of undifferentiated small round cell sarcomas is expected to emerge in the future.

From the ashes of "Ewing-like" sarcoma: A contemporary update of the classification, immunohistochemistry, and molecular genetics of round cell sarcomas

Round cell sarcomas include a diverse group of bone and soft tissue tumors, which comprise well-defined entities as well as several nascent categories presented in the 2020 World Health Organization classification. The morphologic overlap yet disparate nosology, prognostic implications, and management strategies places a high value on ancillary testing, including a strategic immunohistochemical approach and directed confirmation by cytogenetic and molecular genetic methods. We review the diagnostic categories that have emerged from the former wastebasket "undifferentiated round cell sarcoma" ("Ewing-like" sarcomas), with an emphasis on algorithmic exclusion of nonsarcomatous entities, diagnostic stratification of well-defined entities (Ewing sarcoma, rhabdomyosarcomas, poorly differentiated synovial sarcoma), and a discussion of the new categories with novel genetic alterations (CIC-rearranged sarcomas, sarcomas with BCOR genetic alterations, and round cell sarcomas with EWSR1-non-ETS fusions).

Ewing Sarcoma and Ewing-Like Sarcoma and the Role of NKX2.2 Immunoreactivity

Ewing sarcoma (ES) belongs to the family of "small round blue cell" tumors and its diagnosis currently involves a combination of immunostaining and molecular analysis. However, due to significant histological overlap with other tumors of the same family, accurate diagnosis has historically involved combining these results with clinical correlation. Recently, multiple studies have analyzed the role of NKX2.2 immunopositivity in the diagnosis of ES. NKX2.2, a downstream target of the Ewing sarcoma breakpoint region-Friend leukemia integration 1 (EWSR1-FLI1) fusion, has been identified as a potential stain to differentiate ES and Ewing-like sarcoma from other small round blue cell tumors. In this study, we examine the histopathological interpretation of five patients. Four cases showed fluorescent in situ hybridization (FISH)-identified EWSR1 rearrangement. In one case, rearrangements of EWSR1 or FUS could not be detected, and a diagnosis of Ewing-like sarcoma was rendered. NKX2.2 was immunopositive in all five cases. Based on this limited dataset, NKX2.2 immunopositivity can significantly support the diagnosis of ES and has the potential to support the diagnosis of fusion-undetected Ewing-like sarcoma in appropriate clinical and histologic settings.

Mesenchymal Tumors of the Mediastinum: An Update on Diagnostic Approach

Mesenchymal tumors of the mediastinum are a heterogenous group of rare tumors with divergent lineages. Mediastinal mesenchymal tumors are diagnostically challenging due to their diversity and morphologic overlap with nonmesenchymal lesions arising in the mediastinum. Accurate histologic diagnosis is critical for appropriate patient management and prognostication. Many mediastinal mesenchymal tumors affect distinct age groups or occur at specific mediastinal compartments. Neurogenic tumors, liposarcoma, solitary fibrous tumor, and synovial sarcoma are common mesenchymal tumors in the mediastinum. Herein, we provide an update on the diagnostic approach to mediastinal mesenchymal tumors and a review of the histologic features and differential diagnosis of common benign and malignant mesenchymal tumors of the mediastinum.

Primary uterine Ewing sarcoma - A case report

OBJECTIVE

Ewing sarcoma is a type of neuroectodermal tumors (Ewing family of tumors-EFT) that mostly affect the bone or soft tissue. Primary uterine Ewing sarcoma is extremely rare.

CASE REPORT

We report a case of a primary uterine Ewing sarcoma in a 46-year-old patient, treated with total abdominal hysterectomy, and bilateral salpingo-oophorectomy and following adjuvant chemotherapy with 6 cycles of vincristine, doxorubicin, and cyclophosphamide, achieving complete remission for one year.

CONCLUSION

Complete resection for EFT is the first choice of treatment, regardless of their origins. Adjuvant chemotherapy or radiotherapy is mandatory if needed. Due to rarity of the disease, this report re-emphasizes the accurate diagnosis and appropriate treatment for these unusual tumor types occurred in female genital organs.

Distantly Metastatic Retinoblastoma to Soft Tissue and Bone: A Challenging Diagnosis Highlighting the Utility of CRX

Distant metastasis of retinoblastoma to sites outside the central nervous system is rare; such cases may present years following primary treatment. Diagnosis may be difficult given the rarity of such events and considerable histologic mimics. We describe the clinicopathologic features of 6 cases of metastatic retinoblastoma to distant bone and soft tissue sites from 2 large academic centers. Patients were 3 female and 3 male children; median age was 9.5 years (range: 5 to 15 y) with a mean interval from primary disease diagnosis of 8.0 years (range: 0.75 to 14 y). Metastasis to bones of the lower extremities was most common, occurring in 4 of 6 cases. Tumors showed typical histologic features of retinoblastoma, with sheets of primitive round cells with minimal cytoplasm and indistinct nucleoli; however, characteristic Flexner-Wintersteiner rosettes were absent. A subset of cases demonstrated an alveolar growth pattern, and 2 cases showed higher grade cytology with nuclear anaplasia and prominent nucleoli. Immunohistochemistry for CRX and RB1 showed uniform positivity and loss of expression, respectively. Metastatic retinoblastoma outside the central nervous system may present following long disease-free intervals. Immunohistochemistry for CRX is helpful to confirm this challenging diagnosis.

Integrated diagnosis based on transcriptome analysis in suspected pediatric sarcomas

Pediatric solid tumors are a heterogeneous group of neoplasms with over 100 subtypes. Clinical and histopathological diagnosis remains challenging due to the overlapping morphological and immunohistochemical findings and the presence of atypical cases. To evaluate the potential utility of including RNA-sequencing (RNA-seq) in the diagnostic process, we performed RNA-seq in 47 patients with suspected pediatric sarcomas. Histopathologists specialized in pediatric cancer re-evaluated pathological specimens to reach a consensus diagnosis; 42 patients were diagnosed with known subtypes of solid tumors whereas 5 patients were diagnosed with undifferentiated sarcoma. RNA-seq analysis confirmed and refined consensus diagnoses and further identified diagnostic genetic variants in four of the five patients with undifferentiated sarcoma. Genetic lesions were detected in 23 patients, including the novel SMARCA4-THOP1 fusion gene and 22 conventional or recently reported genetic events. Unsupervised clustering analysis of the RNA-seq data identified a distinct cluster defined by the overexpression of rhabdomyosarcoma-associated genes including MYOG and CHRNG. These findings suggest that RNA-seq-based genetic analysis may aid in the diagnosis of suspected pediatric sarcomas, which would be useful for the development of stratified treatment strategies.

EWSR1-The Most Common Rearranged Gene in Soft Tissue Lesions, Which Also Occurs in Different Bone Lesions: An Updated Review

EWSR1 belongs to the FET family of RNA-binding proteins including also Fused in Sarcoma (FUS), and TATA-box binding protein Associated Factor 15 (TAF15). As consequence of the multifunctional role of EWSR1 leading to a high frequency of transcription of the chromosomal region where the gene is located, EWSR1 is exposed to aberrations such as rearrangements. Consecutive binding to other genes leads to chimeric proteins inducing oncogenesis. The other TET family members are homologous. With the advent of widely used modern molecular techniques during the last decades, it has become obvious that EWSR1 is involved in the development of diverse benign and malignant tumors with mesenchymal, neuroectodermal, and epithelial/myoepithelial features. As oncogenic transformation mediated by EWSR1-fusion proteins leads to such diverse tumor types, there must be a selection on the multipotent stem cell level. In this review, we will focus on the wide variety of soft tissue and bone entities, including benign and malignant lesions, harboring EWSR1 rearrangement. Fusion gene analysis is the diagnostic gold standard in most of these tumors. We present clinicopathologic, immunohistochemical, and molecular features and discuss differential diagnoses.

A 22-Year-Old Man With Back Pain, Dilated Veins Over Chest, and Mass in Right Atrium

CASE PRESENTATION

A 22-year-old nonsmoker male, without any previous comorbidity, presented with 4 months' history of right upper back pain. Pain was constant dull aching type, nonpleuritic, aggravated by lying on the right lateral side and partially relieved on taking analgesics. He then developed progressive dyspnea over 2 months and noticed dilated veins over his neck and front of chest. There was associated unintentional weight loss of 6 kg. There was no history of cough, expectoration, wheeze, or hemoptysis, nor any episodes of night sweats or fever.

NKX6-1 mediates cancer stem-like properties and regulates sonic hedgehog signaling in leiomyosarcoma

Background

Leiomyosarcoma (LMS), the most common soft tissue sarcoma, exhibits heterogeneous and complex genetic karyotypes with severe chromosomal instability and rearrangement and poor prognosis.

Methods

Clinical variables associated with NKX6-1 were obtained from The Cancer Genome Atlas (TCGA). NKX6-1 mRNA expression was examined in 49 human uterine tissues. The in vitro effects of NXK6-1 in LMS cells were determined by reverse transcriptase PCR, western blotting, colony formation, spheroid formation, and cell viability assays. In vivo tumor growth was evaluated in nude mice.

Results

Using The Cancer Genome Atlas (TCGA) and human uterine tissue datasets, we observed that NKX6-1 expression was associated with poor prognosis and malignant potential in LMS. NKX6-1 enhanced in vitro tumor cell aggressiveness via upregulation of cell proliferation and anchorage-independent growth and promoted in vivo tumor growth. Moreover, overexpression and knockdown of NKX6-1 were associated with upregulation and downregulation, respectively, of stem cell transcription factors, including KLF8, MYC, and CD49F, and affected sphere formation, chemoresistance, NOTCH signaling and Sonic hedgehog (SHH) pathways in human sarcoma cells. Importantly, treatment with an SHH inhibitor (RU-SKI 43) but not a NOTCH inhibitor (DAPT) reduced cell survival in NKX6-1-expressing cancer cells, indicating that an SHH inhibitor could be useful in treating LMS. Finally, using the TCGA dataset, we demonstrated that LMS patients with high expression of NKX6-1 and HHAT, an SHH pathway acyltransferase, had poorer survival outcomes compared to those without.

Conclusions

Our findings indicate that NKX6-1 and HHAT play critical roles in the pathogenesis of LMS and could be promising diagnostic and therapeutic targets for LMS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00726-6.