An unusual cystic presentation of pelvic skeletal Ewing sarcoma: a case series.

Ewing sarcoma (ES) is the second most common primary malignant bone tumour in children and adolescents. About 14.5% of primary malignancies develop in pelvic bones, where they typically have worse prognoses than extremity or acral sarcomas. It usually presents with aggressive features on radiology scans, but may also present with different radiological characteristics. In this series, we describe rare appearances of pelvic skeletal Ewing sarcoma, with large extraosseous cystic component on imaging, defined by the presence of fluid-filled spaces in the extraosseous tumour lesion, which distinguishes it from the solid nature of conventional ES. We report 3 cases of cystic presentation of ES, with imaging features supporting diagnosis of a primary malignant bone tumour arising from the superior pubic ramus with associated massive intrapelvic solid and cystic mass. CT-guided biopsy provided diagnosis of ES, with large intrapelvic soft tissue and cystic component. These patients underwent neo-adjuvant chemotherapy and proton beam therapy with significant reduction in size of the solid components, while the cystic components remained relatively unchanged. Two patients underwent surgical resection of the tumour (navigated P3 internal hemipelvectomy and hemipelvis P2/P3 resection, respectively), and one patient died while on treatment. In both who underwent surgery, histology showed ES with margins clear and more than 99% of treatment-induced necrosis. To the authors' knowledge, this unusual presentation of pelvic ES is described for the first time in the literature as a case series, with particular reference to atypical extraosseous cystic changes, along with the clinical and radiological characteristics, and their treatment.

Xanthogranulomatous epithelial tumor: report of 6 cases of a novel, potentially deceptive lesion with a predilection for young women.

Epithelial marker expression and/or epithelial differentiation, as well as "anomalous" expression of keratins, are features of some soft tissue tumors. Recently, we have encountered an unusual mesenchymal tumor composed of bland, distinctly eosinophilic, keratin-positive epithelial cells, which were almost entirely obscured by xanthogranulomatous inflammation. Six cases were identified (5 F, 1 M; 16-62 years (median 21 years)) arising in soft tissue (n = 4) and bone (n = 2) and ranging in size from 2 to 7 cm. The tumors were generally circumscribed, with a fibrous capsule containing lymphoid aggregates, and consisted in large part of a sheet-like proliferation of foamy histiocytes, Touton-type and osteoclast-type giant cells, and chronic inflammatory cells. Closer inspection, however, disclosed a distinct population of uniform, cytologically bland mononuclear cells with brightly eosinophilic cytoplasm arranged singly and in small nests and cords. Overt squamous and/or glandular differentiation was absent. By immunohistochemistry, these cells were diffusely positive with the OSCAR and AE1/AE3 keratin antibodies, and focally positive for high-molecular weight keratins; endothelial and myoid markers were negative and SMARCB1 was retained. RNA-seq identified a PLEKHM1 variant of undetermined significance in one case, likely related to this patient's underlying osteopetrosis. Follow-up to date has been benign. In summary, we have identified a novel tumor of soft tissue and bone with a predilection for young females, provisionally termed "xanthogranulomatous epithelial tumor". These unusual lesions do not appear to arise from adnexa, or represent known keratin-positive soft tissue tumors, and the origin of their constituent epithelial cells is obscure. The natural history of this distinctive lesion appears indolent, although study of additional cases and longer term follow-up are needed.

ETV transcriptional upregulation is more reliable than RNA sequencing algorithms and FISH in diagnosing round cell sarcomas with CIC gene rearrangements.

CIC rearrangements have been reported in two-thirds of EWSR1-negative small blue round cell tumors (SBRCTs). However, a number of SBRCTs remain unclassified despite exhaustive analysis. Fourteen SBRCTs lacking driver genetic events by RNA sequencing (RNAseq) analysis were collected. Unsupervised hierarchical clustering was performed using samples from our RNAseq database, including 13 SBRCTs with non-CIC genetic abnormalities and 2 CIC-rearranged angiosarcomas among others. Remarkably, all 14 study cases showed high mRNA levels of ETV1/4/5, and by unsupervised clustering most grouped into a distinct cluster, separate from other tumors. Based on these results indicating a close relationship with CIC-rearranged tumors, we manually inspected CIC reads in RNAseq data. FISH for CIC and DUX4 abnormalities and immunohistochemical stains for ETV4 were also performed. In the control group, only 2 CIC-rearranged angiosarcomas had high ETV1/4/5 expression. Upon manual inspection of CIC traces, 7 of 14 cases showed CIC-DUX4 fusion reads, 2 cases had DUX4-CIC reads, while the remaining 5 were negative. FISH showed CIC break-apart in 7 cases, including 5 cases lacking CIC-DUX4 or DUX4-CIC fusion reads on RNAseq manual inspection. However, no CIC abnormalities were detected by FISH in 6 cases with CIC-DUX4 or DUX4-CIC reads. ETV4 immunoreactivity was positive in 7 of 11 cases. Our results highlight the underperformance of FISH and RNAseq methods in diagnosing SBRCTs with CIC gene abnormalities. The downstream ETV1/4/5 transcriptional up-regulation appears highly sensitive and specific and can be used as a reliable molecular signature and diagnostic method for CIC fusion positive SBRCTs.

Unusual soft tissue metastases in a patient with chondrosarcoma: a case report.

Chondrosarcoma (CS) is the second most frequent primary malignant bone tumour, characterized by production of non-osteoid cartilage matrix. Up to more than 30% of patients with CS present distant metastases, and the lungs represent the preferred site. Hence, CS soft tissue metastases and superficial cutaneous lesions are extremely rare. We report the case of a female who developed unusual multiple soft tissue CS metastases. This patient underwent left hindquarter amputation for recurrent grade 3 chondrosarcoma of the femoral neck with extension to the pelvis approximately 4 years after internal fixation with an intramedullary nail for pathological fracture of left proximal femur and subsequent total proximal femoral endoprosthetic replacement for grade 1-2 chondrosarcoma. In the following years, she underwent metastasectomy for several grade 2 pulmonary metastatic chondrosarcomas. More than 14 years after the amputation, she presented with multiple unusual superficial cutaneous lesions, and a whole-body magnetic resonance imaging demonstrated multiple soft tissue foci of metastatic disease. The histology of multiple soft tissue lesions excised confirmed metastatic chondrosarcoma. Then, she underwent marginal excision of further multifocal soft tissue metastatic high-grade chondrosarcoma. Unlike the poor survival from the onset of these metastases in the other cases reported in the literature, our patient is still alive 2 years after the first multiple soft tissue excision of metastatic chondrosarcoma, and approximately 20 years after the diagnosis of chondrosarcoma. Soft tissue CS metastases are a rare entity with few cases described in literature. This study aims to make the reader aware of this lesser-known CS manifestation.

An unusual case of metastatic melanoma in subcutaneous tissue presenting as a solitary cystic mass with fluid levels.

Malignant melanoma is a common and often aggressive neoplasm of the skin arising from melanocytes. Metastatic melanoma is known for its diverse clinical manifestations, and can present with atypical features prior to diagnosis of the primary lesion, which can pose a diagnostic challenge. We report a rare case of metastatic melanoma in a 67 year-old male who presented with a painless, enlarging mass in the right axilla over a 4 week period. Ultrasound and magnetic resonance imaging (MRI) scans revealed a well-defined solitary, cystic appearing lesion in the right axilla with a distinct fluid-fluid level. An ultrasound guided biopsy of the lesion diagnosed a metastatic melanoma. While haemorrhagic distant metastases are a well-recognised complication of malignant melanoma, particularly in the brain and lung, soft tissue metastases presenting with fluid-fluid levels is not well described in the literature. The case highlights the importance of considering the differential of melanoma metastasis when encountered with such a lesion and importance of ultrasound guided biopsy for histopathological confirmation, as the imaging features can mimic that of a haemorrhagic soft tissue sarcoma, the management of which differs substantially from that of melanoma.

EWSR1 Fusions With CREB Family Transcription Factors Define a Novel Myxoid Mesenchymal Tumor With Predilection for Intracranial Location.

Recurrent gene fusions involving EWSR1 with members of the cAMP response element binding protein (CREB) family (ATF1 and CREB1) have been reported in a diverse group of tumors including angiomatoid fibrous histiocytoma (AFH), soft tissue and gastrointestinal clear cell sarcoma, primary pulmonary myxoid sarcoma, and hyalinizing clear cell carcinoma of salivary gland. We have recently encountered a group of 5 myxoid mesenchymal tumors positive for EWSR1 fusions with one of the CREB family member (ATF1, CREB1, and CREM), with histologic features distinct from any of the previously described pathologic entities. Tumors occurred in children or young adults (12 to 23 y; mean, 18 y), with equal sex distribution. All except 1 were intracranial (intra-axial, 2; meningeal, 2), whereas 1 was perirectal. Histologically, the tumors were well circumscribed, often lobulated, composed of uniform ovoid to round cells, and arranged in cord-like or reticular structures in a myxoid background. All except 1 displayed unique sunburst amianthoid fibers. Immunohistochemically, tumors were positive for epithelial membrane antigen (5/5; 4 focal, 1 diffuse) and desmin (3/5). A novel EWSR1-CREM fusion was identified by RNA sequencing in the perirectal tumor, which was further confirmed by fluorescence in situ hybridization (FISH) and reverse transcription-polymerase chain reaction (RT-PCR). A second case with similar EWSR1-CREM fusion was identified by RT-PCR and FISH in a meningeal tumor. The remaining cases studied by FISH showed the presence of EWSR1-CREB1 fusion in 2 cases and EWSR1-ATF1 in 1. In conclusion, we report a distinct group of myxoid mesenchymal neoplasms occurring in children or young adults with a predilection for intracranial locations. Although the immunoprofile [epithelial membrane antigen (EMA), desmin] and the fusion type raise the possibility of a myxoid AFH, none of the typical histologic findings of AFH were present, suggesting a novel entity.

Complete resection of a large phosphaturic mesenchymal tumour by chest wall resection and reconstruction.

Phosphaturic mesenchymal tumour is an extremely rare mesenchymal neoplasm of bone or soft tissue. It is associated with paraneoplastic oncogenic osteomalacia through secretion of fibroblast growth factor-23 (FGF-23) which inhibits renal proximal tubule phosphate re-uptake. We report a case of a 36-year-old woman with a large chest wall tumour completely excised by extensive chest wall resection and reconstruction with polypropylene mesh-methylmethacrylate composite and pedicled muscle flaps.

Novel BCOR-MAML3 and ZC3H7B-BCOR Gene Fusions in Undifferentiated Small Blue Round Cell Sarcomas.

Small blue round cell tumors (SBRCTs) are a heterogenous group of tumors that are difficult to diagnose because of overlapping morphologic, immunohistochemical, and clinical features. About two-thirds of EWSR1-negative SBRCTs are associated with CIC-DUX4-related fusions, whereas another small subset shows BCOR-CCNB3 X-chromosomal paracentric inversion. Applying paired-end RNA sequencing to an SBRCT index case of a 44-year-old man, we identified a novel BCOR-MAML3 chimeric fusion, which was validated by reverse transcription polymerase chain reaction and fluorescence in situ hybridization techniques. We then screened a total of 75 SBRCTs lacking EWSR1, FUS, SYT, CIC, and BCOR-CCNB3 abnormalities for BCOR break-apart probes by fluorescence in situ hybridization to detect potential recurrent BCOR gene rearrangements outside the typical X-chromosomal inversion. Indeed, 8/75 (11%) SBRCTs showed distinct BCOR gene rearrangements, with 2 cases each showing either a BCOR-MAML3 or the alternative ZC3H7B-BCOR fusion, whereas no fusion partner was detected in the remaining 4 cases. Gene expression of the BCOR-MAML3-positive index case showed a distinct transcriptional profile with upregulation of HOX-gene signature, compared with classic Ewing's sarcoma or CIC-DUX4-positive SBRCTs. The clinicopathologic features of the SBRCTs with alternative BCOR rearrangements were also compared with a group of BCOR-CCNB3 inversion-positive cases, combining 11 from our files with a meta-analysis of 42 published cases. The BCOR-CCNB3-positive tumors occurred preferentially in children and in bone, in contrast to alternative BCOR-rearranged SBRCTs, which presented in young adults, with a variable anatomic distribution. Furthermore, BCOR-rearranged tumors often displayed spindle cell areas, either well defined in intersecting fascicles or blending with the round cell component, which appears distinct from most other fusion-positive SBRCTs and shares histologic overlap with poorly differentiated synovial sarcoma.

High grade osteosarcoma on a background of trichorhinophalangeal syndrome: A family perspective.

Trichorhinophalangeal syndrome (TRPS) is a rare genetic disorder with typical craniofacial and skeletal abnormalities. Three main subtypes have been described. All variations of the condition affect the hair (tricho), nose (rhino) and fingers (phalangeal). The diagnosis is usually made through clinical examination augmented by hand radiographs that reveal characteristic cone-shaped epiphyses Sporadic case reports detailing TRPS have been described in the literature. We describe the first report of high-grade osteosarcoma presenting in two members of the same family with trichorhinophalangeal syndrome (TRPS).

Functional epigenetic approach identifies frequently methylated genes in Ewing sarcoma.

Using a candidate gene approach we recently identified frequent methylation of the RASSF2 gene associated with poor overall survival in Ewing sarcoma (ES). To identify effective biomarkers in ES on a genome-wide scale, we used a functionally proven epigenetic approach, in which gene expression was induced in ES cell lines by treatment with a demethylating agent followed by hybridization onto high density gene expression microarrays. After following a strict selection criterion, 34 genes were selected for expression and methylation analysis in ES cell lines and primary ES. Eight genes (CTHRC1, DNAJA4, ECHDC2, NEFH, NPTX2, PHF11, RARRES2, TSGA14) showed methylation frequencies of>20% in ES tumors (range 24-71%), these genes were expressed in human bone marrow derived mesenchymal stem cells (hBMSC) and hypermethylation was associated with transcriptional silencing. Methylation of NPTX2 or PHF11 was associated with poorer prognosis in ES. In addition, six of the above genes also showed methylation frequency of>20% (range 36-50%) in osteosarcomas. Identification of these genes may provide insights into bone cancer tumorigenesis and development of epigenetic biomarkers for prognosis and detection of these rare tumor types.

RASSF2 methylation is a strong prognostic marker in younger age patients with Ewing sarcoma.

Ras-association domain family of genes consist of 10 members (RASSF1-RASSF10), all containing a Ras-association (RA) domain in either the C- or the N-terminus. Several members of this gene family are frequently methylated in common sporadic cancers; however, the role of the RASSF gene family in rare types of cancers, such as bone cancer, has remained largely uninvestigated. In this report, we investigated the methylation status of RASSF1A and RASSF2 in Ewing sarcoma (ES). Quantitative real-time methylation analysis (MethyLight) demonstrated that both genes were frequently methylated in Ewing sarcoma tumors (52.5% and 42.5%, respectively) as well as in ES cell lines and gene expression was upregulated in methylated cell lines after treatment with 5-aza-2'-deoxcytidine. Overexpression of either RASSF1A or RASSF2 reduced colony formation ability of ES cells. RASSF2 methylation correlated with poor overall survival (p = 0.028) and this association was more pronounced in patients under the age of 18 y (p = 0.002). These results suggest that both RASSF1A and RASSF2 are novel epigenetically inactivated tumor suppressor genes in Ewing sarcoma and RASSF2 methylation may have prognostic implications for ES patients.