Comprehensive Molecular Characterization of a Large Series of Calcified Chondroid Mesenchymal Neoplasms Widening Their Morphologic Spectrum.

Recently, FN1 fusions to receptor tyrosine kinase genes have been identified in soft tissue tumors with calcified chondroid matrix named calcifying chondroid mesenchymal neoplasms (CCMNs). We collected 33 cases of CCMN from the French network for soft tissue and bone tumors. We performed whole-exome RNA sequencing, expression analysis, and genome-wide DNA methylation profiling in 33, 30, and 20 cases of CCMN compared with a control group of tumors, including noncalcified tenosynovial giant cell tumor (TGCT). Among them, 15 cases showed morphologic overlap with soft tissue chondroma, 8 cases with tophaceous pseudogout, and 10 cases with chondroid TGCT. RNA-sequencing revealed a fusion of FN1 in 76% of cases (25/33) with different 5' partners, including most frequently FGFR2 (14 cases), TEK or FGFR1. Among CCMN associated with FGFR1 fusions, 2 cases had overexpression of FGF23 without tumor-induced osteomalacia. Four CCMN had PDGFRA::USP8 fusions; 3 of which had histologic features of TGCT and were located in the hip, foot, and temporomandibular joint (TMJ). All cases with FN1::TEK fusion were located at TMJ and had histologic features of TGCT with or without chondroid matrix. They formed a distinct cluster on unsupervised clustering analyses based on whole transcriptome and genome-wide methylome data. Our study confirms the high prevalence of FN1 fusions in CCMN. In addition, through transcriptome and methylome analyses, we have identified a novel subgroup of tumors located at the TMJ, exhibiting TGCT-like features and FN1::TEK fusions.

"Hemispheric pilocytic astrocytoma" revisited: A comprehensive clinicopathological and molecular series emphasizing their overlap with other glioneuronal tumors.

Pilocytic astrocytomas (PA) typically exhibit distinct clinical, radiological, histopathological, and genetic features. DNA-methylation profiling distinguishes PA according to their location (infratentorial, midline, hemispheric, or spinal). In the hemispheric location, distinguishing PA from glioneuronal tumors remains a common diagnostic challenge for neuropathologists. Furthermore, the current version of the DKFZ classifier seems to have difficulty separating them from gangliogliomas. In this study, after central radiological review, we identified a histopathologically defined set of PA (histPA, n = 11) and a cohort of DNA-methylation defined PA (mcPA, n = 11). Nine out of the 11 histPA matched the methylation class of hemispheric PA, whereas 2 cases were classified at the end of the study as dysembryoplastic neuroepithelial tumors. Similarly, the mcPA cohort contained tumors mainly classified as PA (7/11), but 4 cases were classified as glioneuronal. The analysis of the 16 tumors with an integrated diagnosis of PA revealed that they affect mainly children with a wide spectrum of radiological, histopathological (i.e. a predominantly diffuse growth pattern), and genetic characteristics (large range of mitogen-activated protein kinase alterations). Based on these results, we consider hemispheric PA to be different from their counterparts in other locations and to overlap with other glioneuronal tumors, reinforcing the necessity of interpreting all data to obtain an accurate diagnosis.

Colorectal Adenocarcinoma Mimicking Neuroendocrine Neoplasia on 18 F-FDOPA PET/CT.

ABSTRACT: We present a case of a 48-year-old woman who had previously undergone surgical resection for bladder paraganglioma. An 18 F-FDOPA PET/CT scan performed for suspected colorectal paraganglioma showed intense colorectal uptake associated with adenopathy. Histological examination did not support the presence of a neuroendocrine tumor but instead confirmed the presence of moderately differentiated colorectal adenocarcinoma. Colorectal adenocarcinoma belongs to the list of nonneuroendocrine false-positive tumors that can be detected using 18 F-FDOPA. Therefore, a morphological analysis is important. Thus, 18 F-FDOPA may be a marker for the aggressiveness of colorectal adenocarcinoma.

Comprehensive Immune Profiling Unveils a Subset of Leiomyosarcoma with "Hot" Tumor Immune Microenvironment.

Purpose: To investigate the immune biomarker in Leiomyosarcoma (LMS), which is rare and recognized as an immune cold cancer showing a poor response rate (<10%) to immune checkpoint inhibitors (ICIs). However, durable response and clinical benefit to ICIs has been observed in a few cases of LMS, including, but not only, LMS with tertiary lymphoid structure (TLS) structures. Patients and methods: We used comprehensive transcriptomic profiling and a deconvolution method extracted from RNA-sequencing gene expression data in two independent LMS cohorts, the International Cancer Genome Consortium (ICGC, N = 146) and The Cancer Genome Atlas (TCGA, N = 75), to explore tumor immune microenvironment (TIME) in LMS. Results: Unsupervised clustering analysis using the previously validated two methods, 90-gene signature and Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT), identified immune hot (I-H) and immune high (I-Hi) LMS, respectively, in the ICGC cohort. Similarly, immune active groups (T-H, T-Hi) were identified in the TCGA cohort using these two methods. These immune active ("hot") clusters were significantly associated, but not completely overlapping, with several validated immune signatures such as sarcoma immune class (SIC) classification and TLS score, T cell inflamed signature (TIS) score, immune infiltration score (IIS), and macrophage score (M1/M2), with more patients identified by our clustering as potentially immune hot. Conclusions: Comprehensive immune profiling revealed a subset of LMS with a distinct active ("hot") TIME, consistently associated with several validated immune signatures in other cancers. This suggests that the methodologies that we used in this study warrant further validation and development, which can potentially help refine our current immune biomarkers to select the right LMS patients for ICIs in clinical trials.

A comprehensive analysis of infantile central nervous system tumors to improve distinctive criteria for infant-type hemispheric glioma versus desmoplastic infantile ganglioglioma/astrocytoma.

Recent epigenomic analyses have revealed the existence of a new DNA methylation class (MC) of infant-type hemispheric glioma (IHG). Like desmoplastic infantile ganglioglioma/astrocytoma (DIG/DIA), these tumors mainly affect infants and are supratentorial. While DIG/DIA is characterized by BRAF or RAF1 alterations, IHG has been shown to have receptor tyrosine kinase (RTK) gene fusions (ALK, ROS1, NTRK1/2/3, and MET). However, in this rapidly evolving field, a more comprehensive analysis of infantile glial/glioneuronal tumors including clinical, radiological, histopathological, and molecular data is needed. Here, we retrospectively investigated data from 30 infantile glial/glioneuronal tumors, consecutively compiled from our center. They were analyzed by two experienced pediatric neuroradiologists in consensus, without former knowledge of the molecular data. We also performed a comprehensive clinical, and histopathological examination (including molecular evaluation by next-generation sequencing, RNA sequencing, and fluorescence in situ hybridization [FISH] analyses), as well as DNA methylation profiling for the samples having sufficient material available. The integrative histopathological, genetic, and epigenetic analyses, including t-distributed stochastic neighbor embedding (t-SNE) analyses segregated tumors into 10 DIG/DIA (33.3%), six IHG (20.0%), three gangliogliomas (10.0%), two pleomorphic xanthoastrocytomas (6.7%), two pilocytic astrocytomas (6.7%), two supratentorial ependymomas, ZFTA fusion-positive (6.7%), two supratentorial ependymomas, YAP1 fusion-positive (6.7%), two embryonal tumors with PLAGL2-family amplification (6.7%), and one diffuse low-grade glioma, MAPK-pathway altered. This study highlights the significant differential features, in terms of histopathology (leptomeningeal infiltration, intense desmoplasia and ganglion cells in DIG/DIA and necrosis, microvascular proliferation, and siderophages in IHG), and radiology between DIG/DIA and IHG. Moreover, these results are consistent with the literature data concerning the molecular dichotomy (BRAF/RAF1 alterations vs. RTK genes' fusions) between DIG/DIA and IHG. This study characterized histopathologically and radiologically two additional cases of the novel embryonal tumor characterized by PLAGL2 gene amplification.

Primary thyroid rhabdomyosarcoma in an adult: A challenging case with histomolecular diagnosis and literature review.

INTRODUCTION AND IMPORTANCE: Primary thyroid sarcomas are very rare tumours, accounting for less than 1 % of all thyroid malignancies. We present the fifth case in the literature of primary thyroid rhabdomyosarcoma and the third in adults with, for the first time, an extensive molecular analysis. CASE PRESENTATION: A 61-year-old woman presented with a rapidly progressive neck mass with extensive local invasion of the tumour. CLINICAL DISCUSSION: Histologically, the neoplasm was composed of sheets of pleomorphic or spindle-shaped cells with eosinophilic cytoplasm and few large and very pleomorphic cells admixed with the spindle cell proliferation, without any thyroid epithelial component. Immunohistochemically, the tumour cells were positive for muscular markers and negative for epithelial and thyroid differentiation markers. Molecular tests revealed the presence of NF1, PTEN and TERT pathogenic mutations. Classifying undifferentiated neoplasm with muscular differentiation into the thyroid is challenging as many more common differential diagnoses could be favoured including anaplastic thyroid carcinoma with rhabdoid phenotype, leiomyosarcoma, and other rare sarcomas. CONCLUSION: Primary thyroid rhabdomyosarcoma is extremely rare and can be diagnostically challenging. We emphasize the histological, immunohistochemical and molecular criteria in order to make an accurate diagnosis.

Efficacy and Safety of Adjuvant Radiotherapy in Re-excised Soft-tissue Sarcoma After Unplanned Resection.

INTRODUCTION: The objective of this study was to evaluate the efficacy and safety of adjuvant radiotherapy (aRT) in patients with soft-tissue sarcoma (STS) re-excised after unplanned tumor resection (UPR). MATERIALS AND METHODS: From 2000 to 2015, we retrospectively evaluated patients with STS of limb or trunk who underwent post-UPR re-excision in our expert center and received or not aRT. RESULTS: Median follow-up was 121 months (IQR 94-165). Among the 145 patients, 37 were not treated with aRT (no-RT) and 108 received aRT with a median radiation dose of 50 Gy (IQR 50-60). At 10 years, patients in the aRT and no-RT groups showed a cumulative incidence of local failure (10y-LF) of 14.7% and 37.7%, and a local recurrence-free survival (10y-LRFS) of 61.3% and 45.8%, respectively. Multivariate analysis identified aRT and age ≥70 years as independent predictors of both LF and LRFS, while grade 3 and deep-seated tumor were independent predictors of LRFS. In overall population, 10-year distant metastasis-free survival (10y-DMFS) and overall survival (10y-OS) were 63.7% and 69.4%. In multivariate analyses, age ≥70 years, grade 3, and deep-seated lesion were associated with shorter DMFS and OS. Acute severe adverse events were not significantly increased in aRT group (14.8% vs. 18.1%, P = .85) but dramatically increased if radiation dose exceeded 50 Gy (risk ratio 2.96 compared to ≤50 Gy, P = .04). CONCLUSION: In STS patients re-excised after UPR, 50 Gy aRT was safe and associated with reduced LF and longer LRFS. It seems to be beneficial even in absence of residual disease or in absence of initial adverse prognostic factors.

All pineal tumors expressing germ cell tumor markers are not necessarily germ cell tumors: histopathological and molecular study of a midline primary intracranial sarcoma DICER1-mutant.

Primary intracranial sarcoma DICER1-mutant is a rare and newly recognized tumor type introduced in the 2021 WHO Classification of Central Nervous System Tumors. It is defined as a spindle cell sarcoma dysplaying eosinophilic intracytoplasmic globules, myogenic differentiation, and DICER1 gene mutation, either somatic or germline. Most reported cases were hemispheric except one, recently described in the pineal region. Here, we report the case of a 12 year-old boy with a pineally located tumor. Despite midline location, poorly differenciated morphology and germ cell marker expression, the association of DICER1 and NF1 hotspot mutations and a specific DNA methylation signature finally lead to the diagnosis of primary intracranial sarcoma DICER1-mutant instead of germ cell tumor. Furthermore, our molecular exploratory results involved a pathway, which was not previously evidenced in those DICER1 mutated cerebral sarcoma that is the canonical Wnt signaling driving likely a part of oncogenesis in this newly described pineal entity.

Expanding the molecular spectrum of tenosynovial giant cell tumors.

Background: While great advances in clinical and pathological description of tenosynovial giant cell tumors (TGCT) have been made, TGCT molecular heterogeneity represents an ongoing challenge. The canonical oncogenic fusion CSF1::COL6A3 is not systematically observed, suggesting that other oncogenic mechanisms are involved in tumorigenesis. This study aims to explore by RNA sequencing a retrospective series of tumors diagnosed as TGCT, in order to provide a better description of their molecular landscape and to correlate molecular features with clinical data. Methods: We analyzed clinicopathological data and performed whole-exome RNA sequencing on 41 TGCT samples. Results: RNAseq analysis showed significant higher CSF1 and CSF1-R expression than a control panel of 2642 solid tumors. RNA sequencing revealed fusion transcripts in 14 patients including 6 not involving CSF1 and some previously unreported fusions. Unsupervised clustering on the expression profiles issued from this series suggested two distinct subgroups: one composed of various molecular subtypes including CSF1 and FN1 rearranged samples and one composed of four tumors harboring an HMGA2::NCOR2 fusion, suggesting distinct tumor entities. Overall, 15 patients received at least one systemic anti-CSF1R treatment and clinical improvement was observed in 11 patients, including patients from both clusters. Discussion: This study reported molecular heterogeneity in TGCT, contrasting with the clinical and pathological homogeneity and the ubiquitous high CSF1 and CSF1R expression levels. Whether molecular diversity may impact the efficacy of systemic treatments needs to be further investigated.

Refining Prognosis in Localized Gastrointestinal Stromal Tumor: Clinical Significance of Phosphatase and Tensin Homolog Low Expression and Gene Loss.

PURPOSE: To investigate the use of PTEN biomarker to improve prognostic stratification in patients with localized gastrointestinal stromal tumor (GIST). METHODS: PTEN expression and genomic analysis were performed on two independent GIST-60 (n = 60) and GIST-100 (n = 100) cohorts, respectively. RESULTS: PTEN expression was significantly lower in patients with local and metastatic recurrent tumor compared with those with no recurrence (P = .004). PTEN low expression was significantly associated with poor disease-free survival (DFS) compared with PTEN high expression (43.73 v 117.95 months; P = .0084) and distant metastatic-free survival (DMFS; 57.95 v 117.95 months; P = .0032). PTEN heterozygous loss was observed in approximately 10% of the patients in each cohort and was associated with poor DFS compared with patients with PTEN normal status (27.56 months v not reached [NR]; P < .001) and DMFS (27.56 months v NR; P < .001). Multivariate analysis revealed that PTEN expression was an independent clinical prognosis factor besides tumor size, mitosis index, and location (hazard ratio for DFS: 3.8; P = .033; hazard ratio for DMFS 5.7, P = .01). Furthermore, PTEN low expression was independently associated with poor DMFS in clinically high-risk patients (mDMFS: 42.28 v 65.61 months; P = .0166). In addition, PTEN heterozygous loss was independently associated with poor DMFS in patients at either low/intermediate risk (mDMFS: 18.05 months for PTEN loss v NR for PTEN normal status; P < .001) or at high risk (mDMFS: 27.19 months for PTEN loss v 105.36 months for PTEN normal status; P = .044). CONCLUSION: PTEN low expression/gene loss is an independent significant prognostic factor and a promising component to strengthen the clinical prognostic tools in patients with localized GIST.

Identification of a novel translocation producing an in-frame fusion of TAF15 and ETV4 in a case of extraosseous Ewing sarcoma revealed in the prenatal period.

Ewing sarcoma (ES) is a highly malignant round cell sarcoma, characterized by gene fusion involving FET (FUS, EWSR1, TAF15) and ETS family genes, respectively. The involvement of the EWSR1 gene has been reported in approximately 90% of cases of ES, with the EWSR1::FLI1 fusion being the most frequent. We report the case of a newborn with a localized soft tissue paravertebral neoplasm diagnosed prenatally. Histopathology and immunophenotype were consistent with a CD99 + , NKX2.2 + undifferentiated round cell sarcoma (URSC); whole-exome RNA-sequencing demonstrated an undescribed in-frame TAF15::ETV4 fusion transcript, while consensus clustering analysis showed high transcriptomic proximity to the ES group. Given clinical context, high tumor chemosensitivity to ES conventional drugs, morphological characteristics, nature of the fusion partners involved, and high transcriptomic proximity to bona fide ESs, this case may represent a new genetic variant of ES.

Desmoid tumors located in the abdomen or associated with adenomatous polyposis: French intergroup clinical practice guidelines for diagnosis, treatment, and follow-up (SNFGE, FFCD, GERCOR, UNICANCER, SFCD, SFED, SFRO, ACHBT, SFR).

INTRODUCTION: Desmoid tumor (DT) of the abdomen is a challenging and rare disease. The level of evidence available to document their treatment is relatively low, however, recent publications of prospective studies have allowed to precise their management. METHODS: This document is a summary of the French intergroup guidelines realized by all French medical and surgical societies involved in the management of DT located in the abdomen or associated with adenomatous polyposis. Recommendations are graded in four categories (A, B, C and D), according to the level of evidence found in the literature until January 2021. RESULTS: When the diagnosis of DT is suspected a percutaneous biopsy should be performed when possible. A molecular analysis looking for pathogenic mutations of the CTNNB1 and APC genes should be systematically performed. When a somatic pathogenic variant of the APC gene is present, an intestinal polyposis should be searched. Due to a high rate of spontaneous regression, non-complicated DT should first benefit from an active surveillance with MRI within 2 months after diagnosis to assess the dynamic of tumor growth. The treatment decision must be discussed in an expert center, favoring the less toxic treatments which can include broad spectrum tyrosine kinase inhibitor or conventional chemotherapy (methotrexate-vinblastine). Surgery, outside the context of emergency, should only be considered for favorable location in an expert center. CONCLUSION: French guidelines for DT management were elaborated to help offering the best personalized therapeutic strategy in daily clinical practice as the DT therapeutic landscape is complexifying. Each individual case must be discussed within a multidisciplinary expert team.

Lack of Prognostic Value of CTNNB1 Mutation Profile in Desmoid-Type Fibromatosis.

PURPOSE: This prospective nationwide cohort study aimed to investigate desmoid-type fibromatosis (DF) outcomes, focusing on the prognostic value of CTNNB1 mutations. EXPERIMENTAL DESIGN: ALTITUDES (NCT02867033) was a nationwide prospective cohort study of DF diagnosed between January 2016 and December 2020. At diagnosis, CTNNB1 molecular alterations were identified using next-generation sequencing or Sanger sequencing. The primary endpoint was event-free survival (EFS; progression, relapse, or death). We enrolled 628 patients managed by active surveillance, surgical resection, or systemic treatment as first-line therapy. RESULTS: Overall, 516 (82.2%) patients [368 females (71.3%), median age 40.3 years (range, 1-89)] were eligible for analysis. In 435 (84.3%) cases, there was one CTNNB1 molecular alteration: p.T41A, p.S45F, or p.S45P. The first-line management was active surveillance in 352 (68.2%), surgical resection in 120 (23.3%), and systemic treatments in 44 (8.5%) patients. CTNNB1 mutation distribution was similar across the three therapeutic groups. The median follow-up period was 24.7 (range, 0.4-59.7) months. The estimated 3-year EFS rate was 66.2% [95% confidence interval (CI), 60.5%-71.2%]. DF harboring p.S45F was significantly associated with male sex (P = 0.03), non-abdominal wall sites (P = 0.05), pain (P = 0.007), and large tumor size (P = 0.025). CTNNB1 p.S45F mutation was not significantly associated with EFS, either in univariate (HR, 1.06; 95% CI, 0.65-1.73; P = 0.81) or in multivariate analysis (HR, 0.91; 95% CI, 0.55-1.49; P = 0.71). CONCLUSIONS: We found that CTNNB1 mutation profile was associated with unfavorable prognostic factors but was not a prognostic factor for EFS. See related commentary by Greene and Van Tine, p. 3911.

Wholistic approach: Transcriptomic analysis and beyond using archival material for molecular diagnosis.

Many neoplasms remain unclassified after histopathological examination, which requires further molecular analysis. To this regard, mesenchymal neoplasms are particularly challenging due to the combination of their rarity and the large number of subtypes, and many entities still lack robust diagnostic hallmarks. RNA transcriptomic profiles have proven to be a reliable basis for the classification of previously unclassified tumors and notably for mesenchymal neoplasms. Using exome-based RNA capture sequencing on more than 5000 samples of archival material (formalin-fixed, paraffin-embedded), the combination of expression profiles analyzes (including several clustering methods), fusion genes, and small nucleotide variations has been developed at the Centre Léon Bérard (CLB) in Lyon for the molecular diagnosis of challenging neoplasms and the discovery of new entities. The molecular basis of the technique, the protocol, and the bioinformatics algorithms used are described herein, as well as its advantages and limitations.

Percutaneous Core Needle Biopsy Can Efficiently and Safely Diagnose Most Primary Bone Tumors.

A biopsy is a prerequisite for the diagnosis and evaluation of musculoskeletal tumors. It is considered that surgical biopsy provides a more reliable diagnosis because it can obtain more tumor material for pathological analysis. However, it is often associated with a significant complication rate. Imaging-guided percutaneous core needle biopsy (PCNB) is now widely used as an alternative to surgical biopsy; it appears to be minimally invasive, possibly with lower complication rates. This study evaluates the diagnostic yield of the preferred use of PCNB in a referral center, its accuracy, and its complication rate. The data relating to the biopsy and the histological analysis were extracted from the database of a bone tumor reference center where PCNB of bone tumors was discussed as a first-line option. 196 bone tumors were biopsied percutaneously between 2016 and 2020. They were located in the axial skeleton in 21.4% (42) of cases, in the lower limb in 58.7% (115), and in the upper limb in 19.9% (39) cases. We obtained a diagnosis yield of 84.7% and a diagnosis accuracy of 91.7%. The overall complication rate of the percutaneous biopsies observed was 1.0% (n = 2), consisting of two hematomas. PCNB performed in a referral center is a safe, precise procedure, with a very low complication rate, and which avoids the need for first-line open surgical biopsy. The consultation between pathologist, radiologist, and clinician in an expert reference center makes this technique an effective choice as a first-line diagnosis tool.

Impact of histological subtype on radiological and pathological response after neoadjuvant radiotherapy in soft tissue sarcoma.

BACKGROUND: Evaluation of response to neoadjuvant radiotherapy (NART) does not consider soft tissue sarcoma (STS) heterogeneity. We aimed to investigate radiological and pathological response of 4 major histotypes. METHODS: Extremity or trunk STS patients who received 50 Gy NART between 2009 and 2020 were retrospectively included. Relative variation in tumor size (RVTS) and pathological response were reported in the overall population and in undifferentiated pleomorphic sarcoma (UPS), myxofibrosarcoma (MFS), myxoid liposarcoma (MLS) and synovial sarcoma (SS) patients to identify response modalities of each histotype. RESULTS: Among the 121 included patients, 49, 19, 13 and 11 presented UPS, MFS, MLS and SS. Median RVTS were 0% (IQR -18-+18), +8% (IQR 0-+24), -12% (IQR -20-3) and -11% (IQR -15-9), respectively (p = 0.001). Median viable cells were 10%, 60%, 20% and 70% (p = 0.007). In overall population, pathological complete response and median necrosis were 27.7% and 10% without significant correlation to histotype (p = 0.18 and 0.06). Nineteen (38.8%) UPS specimens presented cysts that were emptied during the sampling process and distorted the microscopic response evaluation. Infiltrative growth pattern was observed in 28% and 38.9% UPS and MFS patients. Five (38.5%) MLS presented mature adipocytes without proven prognostic value. Cysts were observed in 36% of SS specimens. In the absence of initial tumor limits, the great viable cellularity of SS may be overestimated by their nodular aspect. CONCLUSION: After NART, we highlighted disparate response of UPS, frequent progression of MFS, and confirmed MLS and SS radiosensitivity. Response must be interpreted with caution and consider the histotype-specific patterns.

Superficial CD34-positive fibroblastic tumor and PRDM10-rearranged soft tissue tumor are overlapping entities: a comprehensive study of 20 cases.

AIMS: Superficial CD34-positive fibroblastic tumor (SCD34FT) and PRDM10-rearranged soft tissue tumor (PRDM10-STT) are rare mesenchymal tumors. These lesions have clinicopathological similarities, but their relationship remains controversial. This study aimed to characterise a series of cases of SCD34FT and PRDM10-STT. METHODS AND RESULTS: Ten lesions each of SCD34FT and PRDM10-STT were studied using immunohistochemistry, array-comparative genomic hybridisation (aCGH), RNA sequencing and exome sequencing. Tumors mainly occurred in young adults, were generally small (< 5 cm) and arose predominantly in the superficial soft tissues of the lower extremities. Follow-up data were available in 15 cases (SCD34FT, n = 7, median 16 months; PRDM10-STT, n = 8, median 14 months), local recurrences occurred in four cases (SCD34FT, two of 10; PRDM10-STT, two of 10), while no distant spread was documented. Morphologically, tumors were relatively well-circumscribed and composed of sheets and fascicles of spindle and pleomorphic cells showing low mitotic activity (< 1/mm²) without necrosis. Other findings included: granular cell change, lipoblast-like cells, ectatic blood vessels with fibrinous material, myxoid stromal changes, metaplastic bone and increased mitotic activity (> 1/mm²). All tumors diffusely expressed CD34, while pan-keratin and desmin were commonly seen focally. SynCAM3 was diffusely expressed in 12 cases (SCD34FT, n = 5; PRDM10-STT, n = 7), independently of fusion status. aCGH profiles were 'flat' (PRDM10-STT, n = 4; SCD34FT, n = 2) and exome sequencing showed no recurrent pathogenic mutations (PRDM10-STT, n = 2; SCD34FT, n = 4). Overall, the only morphological features seen exclusively in PRDM10-STT were myxoid stromal changes (three of 10) and metaplastic bone (two of 10). CONCLUSION: We expand the current knowledge on PRDM10-STT and SCD34FT and provide additional evidence for considering them as overlapping entities.

Molecular Classification of Endometrial Stromal Sarcomas Using RNA Sequencing Defines Nosological and Prognostic Subgroups with Different Natural History.

A series of 42 patient tumors diagnosed as endometrial stromal sarcoma (ESS) based on the morphology but negative for JAZF1 and/or YWHAE rearrangement in FISH was analyzed by RNA-sequencing. A chromosomal rearrangement was identified in 31 (74%) of the cases and a missense mutation in known oncogenes/tumor suppressor genes in 11 (26%). Cluster analyses on the expression profiles from this series together with a control cohort composed of five samples of low grade ESS harboring a JAZF1-SUZ12 fusion, one high grade ESS harboring a BCOR-ITD, two uterine tumors resembling ovarian sex cord tumors, two samples each of uterine leiomyoma and leiomyosarcomas and a series of BCOR-rearranged family of tumor (n = 8) indicated that tumors could be gather in three distinct subgroups: one mainly composed of BCOR-rearranged samples that contained seven ESS samples, one mainly composed of JAZF1-fused ESS (n = 15) and the last composed of various molecular subtypes (n = 19). These three subgroups display different gene signatures, different in silico cell cycle scores and very different clinical presentations, natural history and survival (log-rank test, p = 0.004). While YWHAE-NUTM2 fusion genes may be present in both high and low grade ESS, the high-grade presents with additional BCOR or BCORL1 gene mutations. RNAseq brings clinically relevant molecular classification, enabling the reclassification of diseases and the guidance of therapeutic strategy.