Malignant fibrous histiocytoma and fibrosarcoma of bone: a re-assessment in the light of currently employed morphological, immunohistochemical and molecular approaches

From oncogenes to tumor suppressors: The dual role of ncRNAs in fibrosarcoma

Fibrosarcoma is a challenging cancer originating from fibrous tissues, marked by aggressive growth and limited treatment options. The discovery of non-coding RNAs (ncRNAs), including long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and small interfering RNAs (siRNAs), has opened new pathways for understanding and treating this malignancy. These ncRNAs play crucial roles in gene regulation, cellular processes, and the tumor microenvironment. This review aims to explore the impact of ncRNAs on fibrosarcoma's pathogenesis, progression, and resistance to treatment, focusing on their mechanistic roles and therapeutic potential. A comprehensive review of literature from databases like PubMed and Google Scholar was conducted, focusing on the dysregulation of ncRNAs in fibrosarcoma, their contribution to tumor growth, metastasis, drug resistance, and their cellular pathway interactions. NcRNAs significantly influence fibrosarcoma, affecting cell proliferation, apoptosis, invasion, and angiogenesis. Their function as oncogenes or tumor suppressors makes them promising biomarkers and therapeutic targets. Understanding their interaction with the tumor microenvironment is essential for developing more effective treatments for fibrosarcoma. Targeting ncRNAs emerges as a promising strategy for fibrosarcoma therapy, offering hope to overcome the shortcomings of existing treatments. Further investigation is needed to clarify specific ncRNAs' roles in fibrosarcoma and to develop ncRNA-based therapies, highlighting the significance of ncRNAs in improving patient outcomes in this challenging cancer.

Sarcomas with EWSR1::Non-ETS Fusion (EWSR1::NFATC2 and EWSR1::PATZ1)

The wide application of increasingly advanced molecular studies in routine clinical practice has allowed a detailed, albeit still incomplete, genetic subclassification of undifferentiated round cell sarcomas. The WHO classification continues to include provisional molecular entities, whose clinicopathologic features are in the early stages of evolution. This review focuses on the clinicopathologic, molecular, and prognostic features of undifferentiated round cell sarcomas with EWSR1/FUS::NFATC2 or EWSR1::PATZ1 fusions. Classic histopathologic findings, uncommon variations, and diagnostic pitfalls are addressed, along with the utility of recently developed immunohistochemical and molecular markers.

Report and literature review of four cases of EWSR1::NFATC2 round cell sarcoma

BACKGROUND

EWSR1::NFATC2 rearranged sarcomas are a group of rare round, undifferentiated sarcomas with clinicopathological features different from those of Ewing's sarcoma (ES) family and other non-ES sarcomas. We report 4 cases of this rare sarcoma and review their features.

MATERIALS AND METHODS

Four cases of EWSR1::NFATC2 rearranged round cell sarcoma of the bone from the Pathology Department of Peking University People's Hospital were retrospectively studied. Clinical and pathological data were summarized, and immunohistochemical staining, fluorescence in situ hybridization (FISH), and Next-generation sequencing (NGS) were performed. Relevant literature reports were also reviewed.

RESULTS

Among the four cases of EWSR1::NFATC2 rearranged round cell sarcoma, three were male, and one was female, with the age ranged from 14 to 34 years old at diagnosis (mean age: 27.5 years). All tumors were located in the femur and ranged in size from 4 to 8cm (mean 6cm), involving the surrounding soft tissues. All four patients underwent surgical treatment, and three received chemotherapy and radiotherapy postoperatively. Follow-up results showed that all four patients were alive. Histologically, the tumors exhibited small round cell sarcoma phenotype, with the stroma rich in mucin or exhibiting a glassy appearance. The tumor cells diffusely expressed CD99, NKX2.2, NKX3.1 and focal expression of CK and EMA was observed. FISH analysis showed that EWSR1 gene rearrangement was detected in all 4 cases, accompanied by 5' locus amplification. EWSR1::NFATC2 fusion probe demonstrated multi yellow fusion signals. NGS identified EWSR1::NFATC2 breakpoints in exon 9 and exon 3 in all 4 cases. The average follow-up duration of the study group was 88 months (range from 26-180 months). One case experienced both local recurrence and metastasis to the lung and chest wall. One case presented with local recurrence. The remaining two cases did not have the recurrence or metastasis.

CONCLUSION

Although the disease can locally recur and metastasize to the lungs, its mortality rate is significantly lower than that of Ewing sarcoma and other high-grade small round cell undifferentiated sarcomas. Therefore, it supports to classify this tumor as a separate subtype of small round cell sarcoma.

Activity of pazopanib in EWSR1-NFATC2 translocation-associated bone sarcoma

Pazopanib is a multi-kinase inhibitor that is currently approved for treatment of advanced renal cell carcinoma and chemotherapy-refractory soft tissue sarcoma. In this case report, we discuss the case of a patient with a EWSR1-NFATC2 fusion positive bone sarcoma who had exceptional tumor control through using pazopanib and surgery for an overall duration exceeding 5 years. We also review the literature on EWSR1-NFATC2 translocation-associated sarcomas and use of pazopanib in bone sarcomas.

Current research and management of undifferentiated pleomorphic sarcoma/myofibrosarcoma

Undifferentiated pleomorphic sarcoma (UPS), once termed as malignant fibrous histiocytoma, has always been diagnosed exclusively in clinical practice because it lacks any defined resemblance to normal mesenchymal tissue. Although myxofibrosarcoma (MFS) has been separated from UPS due to its fibroblastic differentiation with myxoid stroma, UPS and MFS are still identified as a sarcoma group in terms of molecular landscapes. In this review article, we will describe the associated genes and signaling pathways involved in the process of sarcoma genesis and make a summary of conventional management, targeted therapy, immunotherapy, and some novel potential treatments of UPS/MFS. With the progressive advancements in medical technology and a better understanding about the pathogenic mechanism of UPS/MFS in the coming decades, new lights will be shed on the successful management of UPS/MFS.

Small round cell sarcomas

Undifferentiated small round cell sarcomas (SRCSs) of bone and soft tissue comprise a heterogeneous group of highly aggressive tumours associated with a poor prognosis, especially in metastatic disease. SRCS entities mainly occur in the third decade of life and can exhibit striking disparities regarding preferentially affected sex and tumour localization. SRCSs comprise new entities defined by specific genetic abnormalities, namely EWSR1-non-ETS fusions, CIC-rearrangements or BCOR genetic alterations, as well as EWSR1-ETS fusions in the prototypic SRCS Ewing sarcoma. These gene fusions mainly encode aberrant oncogenic transcription factors that massively rewire the transcriptome and epigenome of the as yet unknown cell or cells of origin. Additional mutations or copy number variants are rare at diagnosis and, depending on the tumour entity, may involve TP53, CDKN2A and others. Histologically, these lesions consist of small round cells expressing variable levels of CD99 and specific marker proteins, including cyclin B3, ETV4, WT1, NKX3-1 and aggrecan, depending on the entity. Besides locoregional treatment that should follow standard protocols for sarcoma management, (neo)adjuvant treatment is as yet ill-defined but generally follows that of Ewing sarcoma and is associated with adverse effects that might compromise quality of life. Emerging studies on the molecular mechanisms of SRCSs and the development of genetically engineered animal models hold promise for improvements in early detection, disease monitoring, treatment-related toxicity, overall survival and quality of life.

Primary Malignant Peripheral Nerve Sheath Tumors of Bone: A Clinicopathologic Reappraisal of 8 Cases

Primary spindle cell and pleomorphic sarcomas of bone represent an exceedingly rare group of mesenchymal malignancies that include "soft tissue" histotypes, as malignant peripheral nerve sheath tumour. Outside the head and neck region, only 36 cases of primary malignant peripheral nerve sheath tumour of bone have been described. We retrieved from our archives eight cases of primary malignant peripheral nerve sheath tumour of bone arising outside the head and neck region, describing their clinical, radiological, and morphologic features. Our series, in which all but one patient died of diseases after a median of seven months, confirms that primary malignant peripheral nerve sheath tumours of bone are aggressive tumours. Pathologists should be aware of this rare histotype. More aggressive and active adjuvant treatments should be investigated.

Rare bone sarcomas: A retrospective analysis of 145 adult patients from the French Sarcoma Group

The benefit of chemotherapy (CT) in rare bone sarcomas is not documented in prospective studies. Our retrospective study from the French sarcoma network for bone tumors ResOs was performed in adult patients (pts) from 1976 to 2014, with histologically verified diagnosis of leiomyosarcomas (LMS), undifferentiated pleomorphic sarcoma (UPS) or radiation-associated sarcomas of bone. The median follow-up was 4.7 years (95% CI: 3.7-6.5). Clinical features, treatment modalities and outcomes were recorded and analyzed from 145 pts (median age 53 years [range 20-87]). Site of disease was extremities (66%) or axial skeleton (34%), 111 (77%) presented with localized and potentially resectable disease. The most common histological subtypes were UPS (58%) and LMS (33%); 58% were high-grade tumors. Surgery was performed in 127 pts. In the 111 localized pts, 28 pts (25%) underwent upfront surgery or exclusive radiotherapy (RT; >50 Gy) without CT, whereas 83 pts (75%) received either neoadjuvant (n = 26) or adjuvant CT (n = 13) or both (n = 44). Neoadjuvant and adjuvant CT was mostly doxorubicin-based (95%/86%) and cisplatin-based (67%/63%). R0 resection was achieved in 59 pts, and a good histological response in 15 patients (25%). Adjuvant RT was performed in 24 (22%) pts. For the whole cohort (n = 145), the 5-year overall survival (OS) rate was 53% [42; 62]. In univariate analysis, age ≤ 60 was associated with a longer disease-free survival (DFS) (P = .0436). Neoadjuvant and adjuvant CT tended to be associated with better DFS (P = .056) with no significant impact on OS in this retrospective series.

The rare primary bone sarcomas: imaging-pathological correlation

Rare primary bone sarcomas are challenging entities both radiologically and pathologically. These include the diagnoses of spindle cell sarcoma (leiomyosarcoma, fibrosarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumor), pleomorphic liposarcoma, and undifferentiated pleomorphic sarcoma. The radiographic and cross-sectional imaging features of each of these tumors are presented, along with current key pathological concepts. Frequently non-specific, the radiological appearances must be correlated with all clinical and pathological information available to enable an accurate diagnosis.

Transarticular epithelioid hemangioma of the ankle-a case of a rare vascular neoplasm

Epithelioid hemangioma of the bone is a rare kind of vascular neoplasm posing a diagnostic challenge because of its ability to mimic malignant tumors. We report a case of a fast-growing, talofibular joint-involving epithelioid hemangioma, which was suspectedly initiated by vascular damage due to trauma and arthroscopy. The ankle mass appeared as a lytic lesion on the CT images and as a T1 hypo-, T2 mildly hyperintense, lobulated structure on the MRI scans. The contrast enhancement pattern was typical to vascular neoplasms. Histologically the lesion consisted of well-formed vessels lined with epithelioid cells with a slightly atypical nuclear morphology, inflammation with a significant number of eosinophils, and low mitotic rate. Immunohistochemistry analysis showed the presence of vascular markers but no rearrangements characteristic of soft tissue sarcomas were registered by the next-generation sequencing. The surgical treatment was curative. The report presents current imaging methods and summarizes the imaging findings of transarticular spreading tumors. The paper also highlights that for the differential diagnosis of vascular tumors showing signs of aggressivity, the pathological analysis is inevitable. Correct diagnosis of the epithelioid hemangioma is essential, as the treatment of more malignant entities is substantially different. An added value of the report is that to the best of our knowledge, a transarticular spreading epithelioid hemangioma of the ankle has never been described before.

Multiscale-omic assessment of EWSR1-NFATc2 fusion positive sarcomas identifies the mTOR pathway as a potential therapeutic target

Sarcomas harboring EWSR1-NFATc2 fusions have historically been categorized and treated as Ewing sarcoma. Emerging evidence suggests unique molecular characteristics and chemotherapy sensitivities in EWSR1-NFATc2 fusion positive sarcomas. Comprehensive genomic profiles of 1024 EWSR1 fusion positive sarcomas, including 14 EWSR1-NFATc2 fusions, were identified in the FoundationCore® database. Additional data from the Gene Expression Omnibus, the Genomics of Drug Sensitivity in Cancer and The Cancer Genome Atlas datasets were included for analysis. EWSR1-NFATc2 fusion positive sarcomas were genomically distinct from traditional Ewing sarcoma and demonstrated upregulation of the mTOR pathway. We also present a case of a 58-year-old male patient with metastatic EWSR1-NFATc2 fusion positive sarcoma who achieved 47 months of disease stabilization when treated with combination mTOR and VEGF inhibition. EWSR1-NFATc2 fusion positive sarcomas are molecularly distinct entities with overactive mTOR signaling; which may be therapeutically targetable. These findings support the use of precision medicine in the Ewing family of tumors.

Primary malignant ossifying fibromyxoid tumour of the bone. A clinicopathologic and molecular report of two cases

Objective

To report the exceptional occurrence of ossifying fibromyxoid tumour (OFMT) as a primary bone lesion. OFMT is a rare soft tissue tumour of uncertain differentiation and variable malignant potential, that occurs in adults with a slight male predominance. It is typically located in the subcutis or in the skeletal muscles of the extremities, followed by trunk or head and neck.

Methods

Two cases of OFMT proven to arise from bone are presented. The first is a 65-year old female with a history of rib "osteosarcoma", presenting with an inferior lobe left lung mass. The second is a man with a lytic lesion of the 5th cervical vertebra that recurred shortly after resection. Following H&E and immunohistochemical examination, tumour samples were analysed by NGS and by break-apart FISH to detect rearrangement of the PHF1 and TFE3 genes.

Results

PHF1 gene-rearrangement was identified by FISH on both the primary and the metastatic lesion of first patient. NGS identified a PHF1(intron1) and EPC1 (exon 10) fusion transcript later confirmed by positive PHF1 rearrangement on FISH in the second case.

Conclusions

The demonstration of PHF1 gene rearrangements represents a fundamental ancillary diagnostic test when presented with challenging examples of OFMT.

Rare Primary Malignant Bone Sarcomas

Simple Summary

Primary malignant bone tumors are infrequent cancers. More than 90% of these neoplasms are classified as osteosarcomas, Ewing sarcomas or chondrosarcomas, and their clinical presentation, diagnosis, and treatment principles are well-established. The entities described in this article, are ultra-rare varieties of bone sarcomas, and there clinical and histological characteristics are not well known. Therefore, they are very difficult to be diagnosed and there is a lot of uncertainty on their treatment. Because of their rarity, it is also extremely difficult to perform clinical research on these cancers. This article creates more awareness of these very rare bone tumors. It explains how to recognize and diagnose each entity and it summarizes the medical scientific literature that is available on these cancers. Increasing awareness and clinical research for these cancers are key elements to improve the prognosis for patients with these diseases in the long term.

Abstract

Rare primary malignant bone sarcomas (RPMBS), other than osteosarcoma, chondrosarcoma, chordoma, and Ewing sarcoma, account for about 5–10% of primary bone tumors and represent a major diagnostic challenge. These tumors include spindle cell and round cell sarcoma entities, hemangiopericytoma-like and vascular tumors. Additionally, several histotypes, traditionally described in the soft tissues, such as myxofibrosarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumor of bone, have been reported in patients with primary bone tumors. While wide surgical resection is the mainstay of local treatment, systemic therapy of these rare entities is controversial. Patients with undifferentiated spindle cell or pleomorphic high-grade tumors of bone, are usually treated with osteosarcoma-like chemotherapy, while patients with round cell and undifferentiated round cell tumors (URCTs), may respond to sarcoma treatment regimens for Ewing sarcoma patients. Studies on analogies and differences among these ultra-rare tumors have seldom been reported. This review describes relevance, clinical aspects, diagnostic procedures, staging, treatment recommendations, and current research in this composite tumor group.

NKX3-1 Is a Useful Immunohistochemical Marker of EWSR1-NFATC2 Sarcoma and Mesenchymal Chondrosarcoma

NK3 homeobox 1 (NKX3-1) is widely accepted as a highly sensitive and specific marker for prostatic adenocarcinoma. Prompted by published transcriptome data showing upregulation of NKX3-1 mRNA expression in EWSR1-NFATC2 sarcoma, we explored the utility of NKX3-1 immunohistochemistry in sarcoma diagnosis. We applied NKX3-1 immunohistochemistry to 11 EWSR1-NFATC2 sarcomas and 168 mimics using whole tissue sections. All EWSR1-NFATC2 sarcomas consisted of uniform small round or ovoid cells, all except 1 showing at least focally the typical growth pattern of nests, cords, or trabeculae within a fibrous/myxoid background. A variable eosinophilic infiltrate was common. NKX3-1 was expressed in 9 of 11 (82%) EWSR1-NFATC2 sarcomas, often diffuse and of moderate or strong intensity. All 12 mesenchymal chondrosarcomas tested were also positive for NKX3-1, with over half showing diffuse staining and moderate or strong intensity. The positive staining was seen only in the primitive small round cell component, whereas the cartilaginous component was mostly negative. Although 1 of 30 osteosarcomas showed focal NKX3-1 positivity, all the remaining 155 cases tested, including 20 Ewing sarcomas, 20 myoepithelial tumors, 11 ossifying fibromyxoid tumors, and 1 FUS-NFATC2 sarcoma were negative for NKX3-1. Our study provides the first evidence that EWSR1-NFATC2 sarcoma and Ewing sarcoma could be distinguished immunohistochemically, adding to the accumulating data that these tumors are phenotypically distinct. We suggest that NKX3-1 may have a diagnostic utility in the evaluation of sarcoma and we also call attention to potential pitfalls in the use of this well-known marker of prostatic adenocarcinoma.

NFATc2-rearranged sarcomas: clinicopathologic, molecular, and cytogenetic study of 7 cases with evidence of AGGRECAN as a novel diagnostic marker

NFATc2-rearranged sarcomas (NFATc2-Sarcomas) are infrequent round cell tumors characterized by EWSR1-NFATc2 fusions and FUS-NFATc2 fusions. Although our knowledge on these neoplasms has increased recently, novel diagnostic tools and more comprehensive series are still needed. Here, we describe the features of a series of seven molecularly confirmed NFATc2-Sarcomas (EWSR1-NFATc2, n = 4; FUS-NFATc2, n = 3) and demonstrate the utility of AGGRECAN immunohistochemistry for their identification. Patients were four males and three females, ranging in age from 19 to 66 years (median: 33). All were primary bone tumors (femur, n = 4; tibia, n = 2; ilium, n = 1), frequently infiltrating the surrounding soft tissues. Treatment often consisted of neoadjuvant chemotherapy and surgery. Follow-up was available for six patients (median 18 months, range 5-102 months), three patients died of disease and four patients are currently alive. Histologically, tumors consisted of monotonous round cells growing in lobules and sheets in variable amounts of fibrous to myxoid stroma. Other findings included spindle cells, corded and trabecular architecture, nuclear pleomorphism, cartilaginous differentiation, and osteoid-like matrix. Histological response to neoadjuvant chemotherapy was poor in all resection specimens available for review (n = 4). Tumors were diffusely positive for AGGRECAN and CD99 (7/7), and a subset expressed Pan-Keratin (AE1-AE3; 3/6), S100 (2/6), BCOR (2/6), ETV-4 (2/5), WT1 (2/6), and ERG (2/5). Desmin, NKX3-1, and SATB2 were negative (0/6). Diffuse AGGRECAN staining was also seen in 8/129 round cell sarcomas used for comparison, including mesenchymal chondrosarcoma (7/26) and CIC-sarcoma (1/26). Array-CGH showed complex karyotypes with recurrent deletions of tumor suppressor genes (CDKN2A/B, TUSC7, and DMD) in three FUS-NFATC2 cases and a simpler profile without homozygous losses in one EWSR1-NFATc2 case. Segmental chromosomal gains covering the loci of the fusion genes were detected in both variants. Overall, our study confirms and expands previous observations on NFATc2-sarcomas and supports that AGGRECAN is a useful biomarker of these tumors.

Establishment of a Jaw Fibrosarcoma Patient-Derived Xenograft and Evaluation of the Tumor Suppression Efficacy of Plumbagin Against Jaw Fibrosarcoma

Background: Head and neck fibrosarcoma is a rare malignant tumor, accounting for about 1% of all head and neck tumors. It can also occur in the jaw bone, for which surgical resection is the main treatment but the recurrence rate is high and the prognosis is usually poor. Due to the lack of models mimicking the biological characteristics of the tumor, there is little progress in the research of the pathogenesis and treatment of fibrosarcoma. Therefore, there is an urgent need to explore a high-fidelity model that can reflect the biological characteristics of fibrosarcoma for the sake of improving the therapeutic outcome and prognosis, and preventing recurrence. Patient-derived xenografts (PDX) may more accurately reflect the human disease, and is an attractive platform to study disease biology and develop treatments and biomarkers. In this study we describe the establishment of jaw fibrosarcoma PDX models and compare PDX tumors to those of human origin.

Methods: Tumor biopsies from a patient with jaw fibrosarcoma were implanted in immunodeficient mice. Primary and PDX tumors were characterized extensively by histology, immunohistochemistry and humanized identification. Based on the finding of our previous preliminary research that plumbagin had an anti-tumor effect against head and neck cancer, we used this model in the present study to evaluate the anti-tumor effect of plumbagin on jaw fibrosarcoma.

Results: The established PDX model maintained the histological and immunohistochemical characteristics of the primary tumor. Plumbagin significantly inhibited the tumor growth in the jaw fibrosarcoma PDX model.

Conclusion: We successfully established a PDX model of jaw fibrosarcoma and demonstrated that this PDX model preserved the important molecular characteristics of the human primary tumor, thus providing a powerful tool for treatment research and new drug development of jaw fibrosarcoma. In addition, plumbagin was found to have an inhibitory effect on the growth of PDX modeled jaw fibrosarcoma, which provides a preliminary research basis for its clinical application.

Primary Osseous Low-Grade Myxofibrosarcoma of Clavicle Presenting With Multiple Skeletal Metastases

Myxofibrosarcoma is a soft tissue neoplasm that usually affects the extremities of the elderly. It usually presents as a slow-growing painless mass that can metastasize to the lung and bone. However, the reported incidence of primary osseous myxofibrosarcoma is very low. Moreover, the metastatic pattern of these bone tumors is largely unknown. We describe a unique case of a young Caucasian male with symptomatic low-grade myxofibrosarcoma arising in the left clavicle, who presented with multiple bone metastases.

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

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

EWSR1-NFATC2 Translocation-associated Sarcoma Clinicopathologic Findings in a Rare Aggressive Primary Bone or Soft Tissue Tumor

In recent years, a novel small round cell sarcoma harboring EWSR1-NFATC2 translocation with immunomorphologic overlap with Ewing sarcoma (ES), myoepithelial tumors, and extraskeletal myxoid chondrosarcoma has emerged. There has not been a case series devoted to describing its detailed clinicopathologic and immunohistochemical characteristics. Six sarcomas harboring EWSR1-NFATC2 fusion transcripts by reverse transcription polymerase chain reaction and amplification of the fusion gene by fluorescence in situ hybridization were identified. The patients were 5 adult men and 1 adult woman. Three were primary bone tumors of the radius and 3 were primary soft tissue tumors. Most tumors showed monomorphic round to epithelioid cells in anastomosing cords and abundant myxohyaline to collagenous extracellular matrix. Two tumors had large areas of a solid, matrix-poor histomorphology. All tumors stained for CD99 and NKX2.2; while EMA, dot-like cytokeratin, and focal WT-1 and SMA were present in some tumors. All but 1 tumor showed poor histologic and radiologic responses to neoadjuvant ES-specific chemotherapy. Local or distant recurrences happened in 4 cases. EWSR1-NFATC2 sarcoma is a novel translocation-associated sarcoma. It presents as either a primary bone or soft tissue tumor, usually exhibits distinctive histopathologic features, and has predilection for long bones of adult men. It consistently shows recurrent fusion gene amplification readily detectable by EWSR1 breakapart fluorescence in situ hybridization, which serves as a diagnostic surrogate. It has potential for local and distant recurrence and histologic progression, and is resistant to Ewing sarcoma-specific chemotherapy.

Rare pancreatic metastasis of undifferentiated pleomorphic sarcoma originating from the pelvis: A case report

INTRODUCTION

Undifferentiated pleomorphic sarcoma (UPS) is a reclassification of malignant fibrous histiocytoma by the World Health Organization in 2002. UPS, the most common soft tissue sarcoma reported in adults, mostly recurs as lung disease. Pancreatic metastasis of UPS is extremely rare. We present a rare case of pelvic UPS with pancreatic metastasis.

PRESENTATION OF CASE

A 69-year-old man was identified as having mediastinal lymphadenopathy on follow-up computed tomography (CT), 2 years after undergoing surgery for gastric adenocarcinoma (pT4aN3M0/IIIC). Subsequent positron emission tomography-CT (PET/CT) indicated pelvic lesions and magnetic resonance imaging (MRI) showed multiple tumors of the left pubis and femur. Histopathology of diagnostic thoracoscopic lymph node dissection and CT-guided needle biopsy of the left pubic lesion showed UPS. Systemic chemotherapy and targeted molecular therapy reduced multiple pelvic and metastatic tumors. Left pubic primary lesion contraction was achieved with intensity-modulated radiation therapy. CT performed 4 years after treatment initiation showed a 40-mm pancreatic head mass. Lesions other than the pancreatic tumor were in remission, and a pancreatoduodenectomy was performed. Histological analysis confirmed pancreatic metastasis of anaplastic pleomorphic sarcoma.

DISCUSSION

Reports of pelvic UPS with pancreatic metastasis, as that of the present case, are extremely rare. UPS is malignant potential tumor, and complete excision is the first treatment option, while the usefulness of chemotherapy or radiation therapy remains uncertain.

CONCLUSIONS

Complete resection is vital for local control in pancreatic metastasis of UPS. Sites of recurrence are rare; hence, patients must be carefully followed up.

Novel NTRK3 Fusions in Fibrosarcomas of Adults

NTRK fusions in malignant tumors are therapeutic targets of tyrosine kinase inhibitors. Because they occur only in a small subset of mesenchymal tumors, knowledge regarding the corresponding histology is important to effectively identify patients who could benefit from targeted therapy. In this study, using RNA sequencing, we identified novel NTRK3 fusions involving related partner genes in 2 adult bone and soft tissue tumors that met the current histologic criteria of fibrosarcoma. Case 1 involved the left radius of a 38-year-old woman, whereas in case 2, the right thigh of a 26-year-old man was affected. Histologically, both tumors consisted of the long fascicular growth of long spindle cells. The tumor in case 1 additionally showed focal myxoid changes. Tumor cells had nonpleomorphic, atypical nuclei, and lacked evidence of a specific line of differentiation. Both tumors showed widespread CD34 immunoreactivity and very limited expression of actin. RNA sequencing detected in-frame fusion transcripts of STRN (exon 3)-NTRK3 (exon 14) in case 1 and STRN3 (exon 3)-NTRK3 (exon 14) in case 2, which were confirmed by reverse transcription polymerase chain reaction and Sanger sequencing. Pan-TRK immunostaining was diffusely positive in both cases. Fluorescence in situ hybridization showed signal patterns compatible with NTRK3 rearrangements in both cases, with case 2 additionally harboring a CDKN2A homozygous deletion. This study expands the clinicopathologic and genetic spectrum of sarcomas associated with NTRK fusions, and suggests that CD34-positive fibrosarcoma of bone and soft tissue could be a good candidate for NTRK testing.

Ewing sarcoma and Ewing-like tumors

Ewing sarcoma (ES) and Ewing-like sarcomas are highly aggressive round cell mesenchymal neoplasms, most often occurring in children and young adults. The identification of novel molecular alterations has greatly contributed to a profound reappraisal of classification, to the extent that the category of undifferentiated round cell sarcoma has significantly shrunk. In fact, in addition to Ewing sarcoma, we currently recognize three main categories: round cell sarcomas with EWSR1 gene fusion with non-ETS family members, CIC-rearranged sarcomas, and BCOR-rearranged sarcomas. Interestingly, despite significant morphologic overlap, most of these entities tend to exhibit morphologic features predictive of the underlying molecular alteration. Ewing sarcoma is the prototype of round cell sarcoma whereas in CIC sarcomas, focal pleomorphism and epithelioid morphology can predominate. BCOR sarcomas often exhibit a spindled neoplastic cell population. NFATC2 sarcoma may exhibit remarkable epithelioid features, and PATZ1 sarcomas often feature a sclerotic background. The differential diagnosis for these tumors is rather broad, and among round cell sarcomas includes alveolar rhabdomyosarcoma, desmoplastic small round cell tumor, poorly differentiated round cell synovial sarcoma, small cell osteosarcoma, and mesenchymal chondrosarcoma. A combination of morphologic, immunohistochemical, and molecular findings allows accurate classification in most cases. A granular diagnostic approach to Ewing sarcoma and Ewing-like sarcomas is justified by significant differences in terms of both response to chemotherapy and overall survival. As all these entities are in part defined by specific fusion genes, a molecular diagnostic approach based on NGS technology should be considered. In consideration of the extreme rarity of many of these tumor entities, referral to expert rare cancer centers or to rare cancer networks represents the best strategy in order to minimize diagnostic inaccuracy, and allow proper patient management.

The Outcome of Patients With Localized Undifferentiated Pleomorphic Sarcoma of the Lower Extremity Treated at Stanford University

BACKGROUND

As a diagnosis of exclusion, Undifferentiated Pleomorphic Sarcoma (UPS) has unclear clinical characteristics. The objective of this retrospective cohort study is to investigate which clinical and prognostic factors of primary lower-extremity UPS will determine failure.

METHODS

We retrospectively reviewed 55 primary lower-extremity UPS cases treated at Stanford between 1998 and 2015. Overall Survival (OS) and Disease-Free Survival (DFS) curves were calculated. Univariate Fisher's Exact Tests were used to examine relationships between disease recurrence, treatment, patient factors, tumor characteristics, and surgical margins.

RESULTS

5-year DFS and OS rates were 60% (95% CI, 45%-72%) and 68% (95% CI, 53%-79%), respectively. The 5-year DFS rate for patients with positive margins was 33.3% (95% CI, 5%-68%) compared with 63% (95% CI, 47%-76%) for patients with negative margins. (Log-rank, P=0.03). The OS rate for those with disease recurrence was 42% % (95% CI, 16%-67%) compared with 76% (95% CI, 59%-87%) for patients who did not have disease recurrence (log-rank, P=0.021). Local failure occurred more frequently with omission of radiation therapy (Fisher's exact test, P=0.009).

CONCLUSIONS

Positive surgical margins are an important prognostic factor for predicting relapse in UPS. Relapse of any kind led to worse OS. Radiation therapy improved local control of disease but had no statistically significant effect on DFS, highlighting the need for improved diagnostics to identify those at highest risk for hematogenous metastasis and for selection of patients for adjuvant systemic treatment.

[Updates to the WHO classification of bone tumours]

The fourth edition of the WHO Classification of Soft Tissue and Bone Tumours, published in 2013, extends the approach to describe genetics and pathology of these tumours in the context of epidemiological, clinical and imaging data, which was adopted in the third edition. Added are a few new entities, reclassifications and renamings. The most important point, also of clinical relevance and with consequences for treatment, is the introduction of a stratification of bone tumours based on their biological behaviour into three groups (benign, intermediate, malignant) in analogy to soft tissue tumours.

EWSR1/FUS-NFATc2 rearranged round cell sarcoma: clinicopathological series of 4 cases and literature review

The classification of bone neoplasms composed of small round cells is experiencing a transformation after the discovery of various gene fusion rearrangements that determine diagnosis, behavior, and response to therapy. We present herein 4 new cases of small round cell tumor of the bone that harbor NFATc2 rearrangements involving either EWSR1 or FUS genes. We studied the clinical presentation, pathologic features, genetics (FISH, targeted RNA sequencing) and outcome in these 4 patients. We also reviewed the literature describing similar cases. All our patients were male. The median age at diagnosis was 33.5 years. All tumors presented in long bones of the extremities as a large destructive mass with a mean size of 12.5 cm. All cases were hypercellular with prominent collagenous stroma and consisted of small to medium size round cells arranged in cords, thin trabeculae, and pseudoacinar structures. Most cases showed focal or diffuse membrane staining for CD99; whereas S100, synaptophysin and chromogranin were negative. EMA showed cytoplasmic staining in one case. Genetic studies identified EWSR1-NFATc2 fusion in 3 cases, and FUS-NFATc2 fusion in one case. Two patients were treated with neoadjuvant chemotherapy using Ewing sarcoma regimens, and surgical excision was performed on 3 patients; necrosis was minimal. Follow-up is limited; after a median follow-up of 8.7 months, one patient developed local recurrence and metastases to the lungs. Poorly differentiated round cell sarcoma with EWSR1/FUS-NFATc2 fusions are uncommon. The tumors have consistent clinical findings, morphology, and immunoprofile that in combination are distinctive and differ from that of Ewing sarcoma. Importantly, these tumors do not respond to Ewing sarcoma chemotherapy regimens.

EWSR1-NFATC2 and FUS-NFATC2 Gene Fusion-Associated Mesenchymal Tumors: Clinicopathologic Correlation and Literature Review

The spectrum of mesenchymal tumors associated with rearrangements of the EWSR1 gene has been growing in recent years due to progress in molecular detection techniques. Originally identified as the gene involved in the pathogenesis of Ewing sarcoma, the EWSR1 gene is now known to be rearranged in diverse clinical and histopathological entities. The NFATC2 gene is one of the many translocation partners of EWSR1 in gene fusions in a morphologically typical, albeit rare, subgroup of mesenchymal tumors. Little is known about the clinical characteristics of tumors containing NFATC2 gene rearrangements since most of the few reports published describe molecular rather than clinical aspects. In the current study, we report three patients with tumors carrying the EWSR1-NFATC2 gene translocation, including one rare primary tumor of soft tissues. Another patient with a benign-appearing bone tumor with a unique FUS-NFATC2 gene translocation is described. In various mesenchymal tumors (e.g., myxoid/round cell liposarcoma, low-grade fibromyxoid sarcoma, or angiomatoid fibrous histiocytoma), the FUS gene, as a member of the TET family, may be alternatively rearranged instead of the EWSR1 gene without any noticeable influence on the microscopical appearance or clinical outcome. This fact seems not to apply to mesenchymal tumors with the involvement of the NFATC2 gene because both in our experience and according to the extensive literature review, they have different properties on the morphological and molecular level. Both ESWSR1-NFATC2 and FUS-NFATC2 fusion-carrying tumors do not show microscopical or clinical features of Ewing sarcoma.

DNA methylation profiling distinguishes Ewing-like sarcoma with EWSR1-NFATc2 fusion from Ewing sarcoma

PURPOSE

Recent studies revealed divergent gene expression patterns in Ewing sarcoma (EwS) with canonical EWSR1-ETS gene fusions and undifferentiated round cell sarcomas (URCS) with EWSR1 rearrangements fused to the non-ETS gene NFATc2. Thus, the question arises whether the latter tumors really belong to EwS.

METHODS

We collected five cases matching the group of URCS with EWSR1-NFATc2 fusion and performed DNA methylation and copy number profiling. Results were compared to methylation data of 30 EwS with various EWSR1-ETS fusions and one EwS with FUS-ERG fusion, 16 URCS with CIC rearrangement and 10 URCS with BCOR alteration and a total of 81 EWSR1-associated soft tissue sarcomas including 7 angiomatoid fibrous histiocytomas, 7 clear cell sarcomas of the soft tissue, 28 desmoplastic small round cell tumors, 10 extraskeletal myxoid chondrosarcomas and 29 myxoid liposarcomas.

RESULTS

Unsupervised hierarchical clustering and t-distributed stochastic neighbor embedding analysis of DNA methylation data revealed a homogeneous methylation cluster for URCS with EWSR1-NFATc2 fusion, which clearly segregated from EwS and the other subtypes. Copy number profiles of EWSR1-NFATc2 cases showed recurrent losses on chromosome 9q and segmental gains on 20q13 and 22q12 involving the EWSR1 and NFATc2 loci, respectively.

CONCLUSION

In summary, URCS with EWSR1-NFATc2 fusion share a distinct DNA methylation signature and carry characteristic copy number alterations, which emphasizes that these sarcomas should be considered separately from EwS.

Bone Sarcoma WithEWSR1-NFATC2Fusion: Sarcoma With Varied Morphology and Amplification of Fusion Gene Distinct From Ewing Sarcoma

Ewing sarcomas are typified by EWSR1 fusion to ETS gene family members. Tumors with fusion partners other than ETS family members and atypical histologic features pose significant diagnostic challenges and controversies as to their classification. In this article, we report a tumor with EWSR1-NFATC2 fusion in the left femur of a 43-year-old man and with unusual morphologic features that resemble undifferentiated high-grade sarcoma. Analysis together with reported cases in the literature shows that tumors with EWSR1-NFATC2 exhibit distinctive clinicopathologic features, including predilection for young male adults, highly variable histology that varies from round cell tumors frequently associated with nuclear irregularity, short spindle cells with nuclear pleomorphism, to myoepithelial tumor-like with or without myxohyaline matrix. They show variable positivity to CD99, frequent expression of cytokeratins, and consistent high-level amplification of EWSR1-NFATC2 fusion gene with distinctive gene expression profile. These tumors thus deserve classification separate from Ewing sarcoma.

New fusion sarcomas: histopathology and clinical significance of selected entities

Many sarcomas contain gene fusions that can be pathogenetic mechanisms and diagnostic markers. In this article we review selected fusion sarcomas and techniques for their detection. CIC-DUX4 fusion sarcoma is a round cell tumor now considered an entity separate from Ewing sarcoma with a more aggressive clinical course, occurrence in older age, and predilection to soft tissues. It is composed of larger cells than Ewing sarcoma and often has prominent necrosis. Nuclear DUX4 expression is a promising immuno histochemical marker. BCOR-CCNB3 fusion sarcoma is cyclin B3-positive, usually occurs in bone or soft tissue of children, and may mimic a poorly differentiated synovial sarcoma. EWSR1-NFATC2 sarcoma may present in bone or soft tissue. It is typically composed of small round cells in a trabecular pattern in a myxoid matrix resembling myoepithelioma. ACTB-GLI1 fusion sarcoma may mimic a skin adnexal carcinoma, showing focal expression of epithelial markers and S100 protein. NTRK-fusion sarcomas include, in addition to infantile fibrosarcoma with ETV6-NTRK3 fusion, LMNA-NTRK1 fusion sarcoma, a low-grade spindle cell sarcoma seen in peripheral soft tissues in children and young adults. Methods to detect gene fusions include next-generation sequencing panels, anchored multiplex polymerase chain reaction systems to detect partner for a known fusion gene, and comprehensive RNA sequencing to detect virtually all gene fusions. In situ hybridization testing using probes for both fusion partners can be used as an alternative confirmation technique, especially in the absence of satisfactory RNA yield. In addition, fusion protein-related and other immunohistochemical markers can have a high specificity for fusion sarcomas.

EWSR1-NFATC2 gene fusion in a soft tissue tumor with epithelioid round cell morphology and abundant stroma: a case report and review of the literature

Mesenchymal round cell tumors are a diverse group of neoplasms defined by primitive, often high-grade cytomorphology. The most common molecular alterations detected in these tumors are gene rearrangements involving EWSR1 to one of many fusion partners. Rare EWSR1-NFATC2 gene rearrangements, corresponding to a t(20;22) gene translocation, have been described in mesenchymal tumors with clear round cell morphology and a predilection for the skeleton. We present a case of a tumor harboring the EWSR1-NFATC2 gene fusion arising in the subcutaneous tissue of a young woman. The tumor exhibited corded and trabecular architecture of epithelioid cells within abundant myxoid and fibrous stroma. The cells showed strong immunoreactivity for NKX2.2, variable CD99, keratin, and epithelial membrane antigen, but were negative for S100 and myoepithelial markers. Importantly, similar to previously reported cases, the clinical course was more indolent than that of Ewing sarcoma. This case highlights the distinctive clinicopathological characteristics of EWSR1-NFATC2 gene fusion-associated neoplasms that distinguish them from Ewing sarcoma.

Synovium as a widespread pathway to the adjacent joint in undifferentiated high-grade pleomorphic sarcoma of the tibia: A case report

RATIONALE

Undifferentiated high-grade pleomorphic sarcoma (UPS), originated from bone, is a rare tumor, accounting for 2% to 5% of all primary maligment bone neoplasms. Skip lesion can be found in undifferentiated high-grade pleomorphic sarcoma of bone (UPS-B). However, the direct invasion across the articular synovium to bone has not been reported previously.

PATIENT CONCERNS

We report an unusual case of a 65-year-old man complained of a year history of pain, swelling, and limitation of activity in the left knee joint. At the proximal tibia, there was extensive invasion of articular synovium, which provides a direct anatomic pathway for the tumor invasion to the adjacent bone, including patella and femoral condyle.

DIAGNOSES

Magnetic resonance imaging was important in defining the marrow involvement and joint invasion, including the thickening articular synovium. Subsequent pathological examination confirmed the diagnosis of UPS.

INTERVENTIONS

The patient underwent an extensive resection of the knee joint, except for the patellar.

OUTCOMES

After operation, routine chemotherapy was performed. Unfortunately, half a year later, soft tissue swelling of whole thigh was found. Then this patient came our hospital again. Positron emission tomography imaging showed there was recurrence of UPS with lung metastasis. A week later, this patient died.

LESSONS

In contrast to frequent infiltration pathway, the articular synovium as a media for this tumor spread is rare. This study adds a better understanding of this direct invasion way to the medical literature.

Malignant fibrous histiocytoma in the right portion of the mandible with metastasis in pancreas

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There is no reported evidence in the literature of malignant fibrous histiocytoma having metastasized in pancreas and stomach.

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The incidence of Malignant fibrous histiocytoma (MFH) in the mandible is not frequent and incidence risk is only 3% of all MFHs in bones.

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Metastasis in extrapulmonary locations are not frequent.

Background

Malignant fibrous histiocytoma is a sarcoma of uncertain origin that can be found both in soft tissues and in bones. It is currently called undifferentiated pleomorphic sarcoma not otherwise specified and it represents a final common pathway in several tumors that are subject to the progress of dedifferentiation.

Local recurrence of the tumor in the same location where it was originated occurs in 20–30% of the total number of soft tissue sarcomas. It is less frequent in limbs and more likely to recur in retroperitoneal sarcomas and in head and neck.

Most tumors grow during the first two years after treatment.

Most sarcoma metastases, especially those in the head and neck (including malignant fibrous histiocytoma) present as a lung disease (90%). Extrapulmonary diseases are not frequent and can occur in lymph nodes (10%), bones (8%) and in the liver (1%).

Case report

61 years old woman with history of malignant fibrous histiocytoma in the right portion of the mandible, resected four years ago. Subsequent checkups did not show any disease. The patient reports a constant abdominal pain not diagnosed, related to a pancreatic nodule.

Conclusion

Malignant fibrous histiocytoma is a potentially curable disease. The most important part of the treatment is complete surgical removal, usually followed by adjuvant radiation therapy. Chemotherapy is a treatment usually used only on those patients with higher recurrence risk or on those showingrecurrence or who have already showed recurrence.

Myxofibrosarcoma: First report of myxofibrosarcoma of bone arising at a bone infarct

Approximately 3300 new primary bone tumors will present to American physicians this year. This small but important group of malignancies has become more defined with developments in pathologic morphology, immunohistochemistry, and molecular studies. As tumor types are better partitioned, their specific characteristics are more readily observed. In this article we present the first reported case of a myxofibrosarcoma of bone developing within a bone infarct. With improved delineation of rarer tumor types, it is expected that additional cases of myxofibrosarcoma of bone will be recognized, potentially arising from a bone infarct. By framing the context, describing the case, and sharing pertinent figures, we hope to facilitate this recognition.

Soft Tissue Tumors Rarely Presenting Primary in Bone; Diagnostic Pitfalls

Primary bone sarcomas represent extremely rare entities. The use of now abolished labels, such as malignant fibrous histiocytoma and hemangiopericytoma, has significantly hampered the chance of identifying specific entities. It is now accepted that a broad variety of mesenchymal malignancies most often arising on the soft tissue may actually present as primary bone lesions. A more accurate morphologic partition is justified based on availability of distinct therapeutic options. An integrated diagnostic approach represents the only way to achieve a correct classification. In consideration of the significant complexity, primary bone sarcomas should ideally be handled in the context of expert centers.

Collaborative Action of Surface Chemistry and Topography in the Regulation of Mesenchymal and Epithelial Markers and the Shape of Cancer Cells

Malignant transformation is associated with enhancement of cell plasticity, which allows cancer cells to survive under different conditions by adapting to their microenvironment during growth and metastatic spread. Much effort has been devoted to understanding the molecular mechanisms of these processes. Although the importance of the extracellular matrix and of surface properties in these mechanisms is evident, the direct impact of distinct physical and chemical surfaces characteristics on cell fate remains unclear. Here, we have addressed this question using HT1080 fibrosarcoma cells as a model. To examine the relationship between surface topography, chemistry, and cell behavior, hydrophobic poly(butyl methacrylate-co-ethylene dimethacrylate) (BMA-EDMA) and hydrophilic poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) (HEMA-EDMA) surfaces with three different topographies (microporous, nanoporous, and nonporous) were generated. These surfaces were then modified by photoinitiated grafting of three different methacrylate monomers to create surface chemistry gradients of either negatively (AMPS) or positively (META) charged or zwitterionic (MDSA) functionalities. Our results show that AMPS promotes cell spreading, but that META abolishes cell growth. META and MDSA grafted on microporous BMA-EDMA produced superhydrophilic surfaces with high globularity and elasticity, which modified the cell phenotype by inhibiting cell spreading, followed by loss of mesenchymal characteristics and a reduction in protein levels of the mesenchymal markers N-cadherin, beta-catenin, p120 catenin, and also of the adaptor proteins vinculin and paxillin that are associated with adhesion and cancer cell invasion. The effect was strengthened along the gradient, suggesting that the density of the functional groups plays a role in this process. On the nanoporous surface, only MDSA grafting resulted in a significant increase in cell number, a reduction in N-cadherin expression, increased beta-catenin and p120 catenin levels, as well as the appearance of the epithelial marker E-cadherin. This indicates that the cancer cells have a high plasticity that is triggered by the collaborative effect of physical and chemical surface properties.

[Protocol for the study of bone tumours and standardization of pathology reports]

Primary bone neoplasms represent a rare and heterogeneous group of mesenchymal tumours. The prevalence of benign and malignant tumours varies; the latter (sarcomas) account for less than 0.2% of all malignant tumours. Primary bone neoplasms are usually diagnosed and classified according to the criteria established and published by the World Health Organization (WHO 2013). These criteria are a result of advances in molecular pathology, which complements the histopathological diagnosis. Bone tumours should be diagnosed and treated in referral centers by a multidisciplinary team including pathologists, radiologists, orthopedic surgeons and oncologists. We analyzed different national and international protocols in order to provide a guide of recommendations for the improvement of pathological evaluation and management of bone tumours. We include specific recommendations for the pre-analytical, analytical, and post-analytical phases, as well as protocols for gross and microscopic pathology.

Refinements in Sarcoma Classification in the Current 2013 World Health Organization Classification of Tumours of Soft Tissue and Bone

The fourth edition of the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone was published in February 2013. The 2013 WHO volume provides an updated classification scheme and reproducible diagnostic criteria, which are based on recent clinicopathologic studies and genetic and molecular data that facilitated refined definition of established tumor types, recognition of novel entities, and the development of novel diagnostic markers. This article reviews updates and changes in the classification of bone and soft tissue tumors from the 2002 volume.

Recurrent adult-type fibrosarcoma of the frontal bone in a child

INTRODUCTION

Primary, adult-type bone fibrosarcoma is an uncommon, malignant spindle-cell tumor of fibroblastic origin, rarely affecting children. Most frequently diagnosed among bone malignancies in the past, improved diagnostic techniques and further restrictive classification criteria have currently made the diagnosis of fibrosarcoma very unusual.

CASE REPORT

We hereby report the case of a 7-year-old child with a right frontal swelling mass. A computed tomography scan showed an osteolytic lesion of the right frontal bone, involving the diploe and the outer table of the skull. An en bloc surgical excision, followed by a thorough immunohistological evaluation, led to the diagnosis of fibroblastic proliferation, with low cellularity and minimal atypias. The patient had four recurrences during the 4-year follow-up. With an increasing histological grade at recurrences, a diagnosis of adult-type fibrosarcoma was made.

CONCLUSION

To the best of the authors' knowledge, this is the first reported case of an adult-type fibrosarcoma arising in the frontal bone of a child.

UK guidelines for the management of bone sarcomas

This document is an update of the British Sarcoma Group guidelines published in 2010. The aim is to provide a reference standard for the clinical care of patients in the UK with bone sarcomas. Recent recommendations by the European Society of Medical Oncology, The National Comprehensive Cancer Network and The National Institute for Health and Care Excellence have been incorporated, and the literature since 2010 reviewed. The standards represent a consensus amongst British Sarcoma Group members in 2015. It is acknowledged that these guidelines will need further updates as care evolves. The key recommendations are that bone pain or a palpable mass should always lead to further investigation and that patients with clinico-radiological findings suggestive of a primary bone tumour at any site in the skeleton should be referred to a specialist centre and managed by a fully accredited bone sarcoma multidisciplinary team. Treatment recommendations are provided for the major tumour types and for localised, metastatic and recurrent disease. Follow up schedules are suggested.

Special AT-rich sequence-binding protein 2 (SATB2) expression is sensitive but may not be specific for osteosarcoma as compared with other high-grade primary bone sarcomas

AIMS

The diagnosis of osteosarcoma, although important for eligibility in clinical trials and proper therapy, may be challenging when no bone or osteoid matrix is identified on biopsy. Therefore, other adjunct tests have been sought to help confirm the diagnosis. Special AT-rich sequence-binding protein 2 (SATB2) has been shown as a reliable marker of osteoblastic differentiation. The aim of this study was to examine SATB2 expression in osteosarcomas and other primary bone sarcomas, in order to evaluate its diagnostic utility in discriminating osteogenic from non-osteogenic sarcomas.

METHODS AND RESULTS

Forty-eight pretreated osteosarcoma biopsies, including 26 whole-section cases and 22 tumours on tissue microarrays, and 36 non-osteogenic bone sarcomas were evaluated. Forty-five of 48 (94%) osteosarcomas showed nuclear immunoreactivity for SATB2 (all whole-slide sections showed expression). Positive SATB2 expression was observed in 11 of 22 (50%) undifferentiated pleomorphic sarcomas (UPSs), and in five of 11 (45%) fibrosarcomas; expression was absent in two pleomorphic rhabdomyosarcomas and in the one leiomyosarcoma. The sensitivity of SATB2 for osteosarcoma was 94%, and the specificity was 55%. Stronger-intensity staining was observed in osteosarcoma (P < 0.0001).

CONCLUSIONS

SATB2 is a sensitive marker for osteosarcoma; however, it is not specific, with expression being observed in other high-grade primary bone sarcomas. Intriguingly, the lack of specificity may suggest that the undifferentiated sarcomas (UPSs and fibrosarcomas) with SATB2 expression actually represent osteosarcomas that produce too little matrix to be detected with routine sampling or consist of osteoblast precursors that do not synthesize matrix.

Infarct-Associated Bone Sarcomas: Multimodality Imaging Findings

OBJECTIVE

The objective of our study was to characterize infarct-associated bone sarcoma and its imaging features.

MATERIALS AND METHODS

Our databases were searched for instances of sarcoma arising in association with osteonecrosis. Demographic and imaging data were recorded. The imaging studies of 258 patients with sarcomas were reviewed to determine whether underlying osteonecrosis was present. Radiographic and MRI studies of patients with bone infarction were reviewed to categorize the various appearances of infarction and to determine if sarcomas tended to arise in a particular pattern. A literature review was performed.

RESULTS

Nine infarct-associated bone sarcomas were found in eight patients: seven malignant fibrous histiocytomas (MFHs) and two osteosarcomas. All occurred in the femur or tibia; multifocal infarction was documented in all patients except one. Sarcomas were commonly associated with a so-called "mature"-type pattern of osteonecrosis-that is, with well-defined calcified margins. Osteolysis of infarct-associated MFHs was often overlooked at initial presentation and was often detected only after pathologic fracture. CT and MRI revealed cortical penetration in all cases; infarct margin disruption was evident, but preservation of fat within the infarct was typical. Increased radiotracer activity with relative central photopenia was characteristic of large infarct-associated bone sarcomas on scintigraphy. All lesions, including those treated at our institution and those found in the literature, were metaphyseal or diaphyseal, and although epiphyseal extension of sarcoma from a metadiaphyseal infarct was common, no purely epiphyseal lesions were encountered.

CONCLUSION

Radiologists must remain vigilant for this rare occurrence, especially in patients with new pain in an area of known bone infarction.

Dendritic cell and histiocytic neoplasms: biology, diagnosis, and treatment

BACKGROUND

Dendritic and histiocytic cell neoplasms are rare malignancies that make up less than 1% of all neoplasms arising in lymph nodes or soft tissues. These disorders have distinctive disease biology, clinical presentations, pathology, and unique treatment options. Morphology and immunohistochemistry evaluation by a hematopathologist remains key for differentiating between these neoplasms. In this review, we describe tumor biology, clinical features, pathology, and treatment of follicular dendritic cell sarcoma, interdigitating dendritic cell sarcoma, indeterminate dendritic cell sarcoma, histiocytic sarcoma, fibroblastic reticular cell tumors, and disseminated juvenile xanthogranuloma.

METHODS

A literature search for articles published between 1990 and 2013 was undertaken. Articles are reviewed and salient findings are systematically described.

RESULTS

Patients with dendritic cell and histiocytic neoplasms have distinct but variable clinical presentations; however, because many tumors have recently been recognized, their true incidence is uncertain. Although the clinical features can present in many organs, most occur in the lymph nodes or skin. Most cases are unifocal and solitary presentations have good prognoses with surgical resection. The role of adjuvant therapy in these disorders remains unclear. In cases with disseminated disease, prognosis is poor and data on treatment options are limited, although chemotherapy and referral to a tertiary care center should be considered. Excisional biopsy is the preferred method of specimen collection for tissue diagnosis, and immunohistochemistry is the most important diagnostic method for differentiating these disorders from other entities.

CONCLUSIONS

Dendritic cell and histiocytic cell neoplasms are rare hematological disorders with variable clinical presentations and prognoses. Immunohistochemistry remains important for diagnosis. Larger pooled analyses or clinical trials are needed to better understand optimal treatment options in these rare disorders. Whenever possible, patients should be referred to a tertiary care center for disease management.

Head and Neck Extranodal Interdigitating Dendritic Cell Sarcoma: Case Report and Review of the Literature

Interdigitating dendritic cell sarcoma (IDCS) is an exceedingly rare neoplasm originating from professional antigen presenting cells normally located in the T zone of the lymph node. The purpose of this report was to describe the first case of the IDCS of the submandibular gland and perform a review of the literature of head and neck IDCS. We present a case of an 81-year-old man with a 5 months history of slowly enlarging painless mass in right submandibular region. Fine needle aspiration cytology was suggestive of squamous cell carcinoma. The patient underwent surgical resection of the right submandibular gland and neck dissection. A malignant spindle cell proliferation involving the submandibular gland and colonizing one laterocervical lymph node was found. Morphology and immunophenotype prompted a differential diagnosis of a metastatic spindle cell melanoma versus an IDCS. Transmission electron microscopy was performed and supported a diagnosis of IDCS. The diagnosis of IDCS is a challenging task and may require a large array of techniques.

Primary osseous inflammatory malignant fibrous histiocytoma masquerading as chronic osteomyelitis

Inflammatory malignant fibrous histiocytoma, in addition to a mass lesion, may present with fever and other constitutional symptoms, mimicking an infectious process. This article presents an extremely rare and unique case of primary osseous inflammatory malignant fibrous histiocytoma, highlighting retrospectively the subtle clinical, radiologic, and pathologic features that can suggest this diagnosis. A 63-year-old woman with a history of nephrectomy for right kidney tuberculosis 20 years ago presented with slowly increasing left hip pain for 6 months. The relatively benign-appearing radiograph and biopsy report of chronic inflammation resulted in curettage and nailing of the lesion. The pathologic diagnosis was chronic osteomyelitis, but culture findings for bacteria and tuberculosis were negative. The patient remained well until 4 months later, when left thigh pain returned with fever and leukocytosis (white blood cell count as high as 20.7×10(9)/L, 80% neutrophils). No source of infection was localized. The patient showed no response to broad-spectrum antibiotics and antituberculous drugs. Radiographs showed substantial enlargement of the femoral lesion and extraosseous extension; biopsy results and review of previous histopathologic findings led to a diagnosis of inflammatory malignant fibrous histiocytoma. The fever gradually resolved and the white blood cell count returned to normal within a few days after segmental resection of the proximal femur tumor and its soft tissue extension. However, deep venous thrombosis developed, resulting in left foot ischemia and toe gangrene, necessitating left below-the-knee amputation. Disseminated metastasis occurred 3 months after tumor resection. The patient declined further aggressive treatment and died 13 months after initial presentation.

Malignant round cell tumor of bone with EWSR1-NFATC2 gene fusion

Gene rearrangements involving the Ewing sarcoma breakpoint region 1 (EWSR1) gene are seen in a broad range of sarcomas and some nonmesenchymal neoplasms. Ewing sarcoma is molecularly defined by a fusion of the EWSR1 gene (or rarely the related FUS gene) to a member of the E26 transformation-specific (ETS) family of transcription factors, frequently the EWSR1-FLI1 fusion. More recently, EWSR1 gene fusion to non-ETS family members, including the nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 2 (NFATC2) gene, has been reported in a histological variant of Ewing sarcoma. Here, we report a malignant round cell tumor of bone with an EWSR1-NFATC2 fusion gene. This report builds upon the unusual morphological and clinical presentation of bone neoplasms containing an EWSR1-NFATC2 fusion gene.

Sarcoma classification: an update based on the 2013 World Health Organization Classification of Tumors of Soft Tissue and Bone

The 2013 World Health Organization Classification of Tumors of Soft Tissue and Bone incorporates changes in tumor classification, as well as new genetic insights into the pathogenesis of many different tumor types that have emerged over the 11 years since the publication of the prior volume. This article reviews changes in the classification of soft tissue and bone sarcomas as well as tumors of intermediate biologic potential in the 2013 World Health Organization volume, new molecular insights into these tumors, and associated surgical and clinical implications.

Low-grade myxofibrosarcoma following a metal implantation in femur: a case report

Myxofibrosarcoma is a myxoid variant of malignant fibrous histiocytoma that most commonly involves the extremities of elderly people. However, a primary myxofibrosarcoma with bone invasion in young adults is extremely rare. Herein, we report the case of a 31-year-old male with a gradually enlarging left thigh mass, who had a history of left femur fracture and received an open reduction and internal fixation with titanium alloy plates and screws 33 months previously. Imaging investigations revealed an irregularly shaped soft tissue mass around the left femur shaft and a partial bone defect in the middle one-third of the left femur. Pathological examination of the resected specimen showed a multi-nodular appearance, abundant myxoid matrix and elongated curvilinear capillaries. Immunohistochemical studies revealed that the tumor cells was positive for VIM and MDM2, and was negative for CK, MSA, SMA, DES, S-100 and CD34. Labeling index of Ki-67 was 25%. Based on the morphological finding and immunostaining, it was diagnosed as a low-grade myxofibrosarcoma. The clinical and imaging examinations did not reveal the evidence of a primary cancer elsewhere, and the patient had no personal or family history of malignancy. To our knowledge, this is the first case of a primary myxofibrosarcoma developed following a fracture and metal implantation in young adults.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1745984882113605.