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OBJECTIVE Distinguishing tumor recurrence from therapy-induced imaging changes (TIIC) on brain MRI in children treated for primary malignant brain tumors may be challenging. The authors aimed to assess the diagnostic ability of multimodal MRI in differentiating TIIC from tumor recurrence. METHODS The authors retrospectively included children with abnormal supratentorial brain MRI findings after treatment for primary malignant brain tumors (regardless of their localization) with complete resection and radiotherapy. A total of 18 patients with TIIC and 25 patients with tumor recurrence were compared, according to structural, apparent diffusion coefficient (ADC), and arterial spin labeling (ASL) imaging data accrued over time. TIIC were defined by a new MRI scan that was stable for at least 1 year or had regressed, or by histopathology findings in specimens obtained when the anomaly was surgically treated. RESULTS The time interval between completion of radiotherapy and the appearance of abnormal brain MRI findings was significantly shorter in the TIIC group compared with the tumor recurrence group (median 6 vs 35 months; p < 0.001). TIIC appeared as foci of increased T2-weighted signal intensity, without nodule, associated with variable contrast enhancement. Tumor recurrence appeared as a well-defined nodule with intermediate signal intensity on T2-weighted images with nodular contrast enhancement. Relative ADC values were significantly higher in the TIIC group (median 1.43 vs 0.88; p < 0.001). Relative ASL–cerebral blood flow (CBF) values were significantly lower in the TIIC group (median 0.27 vs 0.43; p = 0.04). On follow-up MRI, TIIC could progress, regress, or remain stable. In most instances (72%), they decreased in size or remained stable at 4 years of follow-up. CONCLUSIONS MRI features of TIIC include foci of increased signal intensity without a demonstrable nodule on T2-weighted images, high ADC values, and lower ASL-CBF values, whereas tumor recurrence appears as a well-defined nodule with low ADC values and higher ASL-CBF values.

Background MYCN-amplified RB1 wild-type (MYCNARB1+/+) retinoblastoma is a rare but clinically important subtype of retinoblastoma due to its aggressive character and relative resistance to typical therapeutic approaches. Because biopsy is not indicated in retinoblastoma, specific MRI features might be valuable to identify children with this genetic subtype. Purpose To define the MRI phenotype of MYCNARB1+/+ retinoblastoma and evaluate the ability of qualitative MRI features to help identify this specific genetic subtype. Materials and Methods In this retrospective, multicenter, case-control study, MRI scans in children with MYCNARB1+/+ retinoblastoma and age-matched children with RB1-/- subtype retinoblastoma were included (case-control ratio, 1:4; scans acquired from June 2001 to February 2021; scans collected from May 2018 to October 2021). Patients with histopathologically confirmed unilateral retinoblastoma, genetic testing (RB1/MYCN status), and MRI scans were included. Associations between radiologist-scored imaging features and diagnosis were assessed with the Fisher exact test or Fisher-Freeman-Halton test, and Bonferroni-corrected P values were calculated. Results A total of 110 patients from 10 retinoblastoma referral centers were included: 22 children with MYCNARB1+/+ retinoblastoma and 88 control children with RB1-/- retinoblastoma. Children in the MYCNARB1+/+ group had a median age of 7.0 months (IQR, 5.0-9.0 months) (13 boys), while children in the RB1-/- group had a median age of 9.0 months (IQR, 4.6-13.4 months) (46 boys). MYCNARB1+/+ retinoblastomas were typically peripherally located (in 10 of 17 children; specificity, 97%; P < .001) and exhibited plaque or pleomorphic shape (in 20 of 22 children; specificity, 51%; P = .011) with irregular margins (in 16 of 22 children; specificity, 70%; P = .008) and extensive retina folding with vitreous enclosure (specificity, 94%; P < .001). MYCNARB1+/+ retinoblastomas showed peritumoral hemorrhage (in 17 of 21 children; specificity, 88%; P < .001), subretinal hemorrhage with a fluid-fluid level (in eight of 22 children; specificity, 95%; P = .005), and strong anterior chamber enhancement (in 13 of 21 children; specificity, 80%; P = .008). Conclusion MYCNARB1+/+ retinoblastomas show distinct MRI features that could enable early identification of these tumors. This may improve patient selection for tailored treatment in the future. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Rollins in this issue.

NTRK gene fusions have been described in a wide variety of central nervous system (CNS) and soft tissue tumors, including the provisional tumor type "spindle cell neoplasm, NTRK-rearranged" (SCN-NTRK), added to the 2020 World Health Organization Classification of Soft Tissue Tumors. Because of histopathological and molecular overlaps with other soft tissue entities, controversy remains concerning the lineage and terminology of SCN-NTRK.This study included 16 mesenchymal tumors displaying kinase gene fusions (NTRK fusions and one MET fusion) initially diagnosed as infantile fibrosarcomas (IFS), SCN-NTRK, and adult-type fibrosarcomas from the soft tissue, viscera and CNS. We used immunohistochemistry, DNA methylation profiling, whole RNA-sequencing and ultrastructural analysis to characterize them. Unsupervised t-distributed stochastic neighbor embedding analysis showed that 11 cases (2 CNS tumors and 9 extra-CNS) formed a unique and new methylation cluster, while all tumors but one, initially diagnosed as IFS, clustered in a distinct methylation class. All the tumors except one formed a single cluster within the hierarchical clustering of whole RNA-sequencing data. Tumors from the novel methylation class co-expressed CD34 and S100, had variable histopathological grades and frequently displayed a CDKN2A deletion. Ultrastructural analyses evidenced a myofibroblastic differentiation.Our findings confirm that SCN-NTRK share similar features in adults and children and in all locations combine an infiltrative pattern, distinct epigenetic and transcriptomic profiles, and ultrastructural evidence of a myofibroblastic lineage. Further studies may support the use of new terminology to better describe their myofibroblastic nature.

Pre- and post-pubertal testicular tumors are two distinct entities in terms of epidemiology, diagnosis and treatment. Most pre-pubertal tumors are benign; the most frequent are teratomas, and the most common malignant tumors are yolk-sac tumors. Post-pubertal tumors are similar to those found in adults and are more likely to be malignant. Imaging plays a pivotal role in the diagnosis, staging and follow-up. The appearance on ultrasonography (US) is especially helpful to differentiate benign lesions that could be candidates for testis-sparing surgery from malignant ones that require radical orchidectomy. Some specific imaging patterns are described for benign lesions: epidermoid cysts, mature cystic teratomas and Leydig-cell tumors. Benign tumors tend to be well-circumscribed, with decreased Doppler flow on US, but malignancy should be suspected when US shows an inhomogeneous, not-well-described lesion with internal blood flow. Imaging features should always be interpreted in combination with clinical and biological data including serum levels of tumor markers and even intra-operative frozen sections in case of conservative surgery to raise any concerns of malignity. This review provides an overview of imaging features of the most frequent testicular and para-testicular tumor types in children and the value of imaging in disease staging and monitoring children with testicular tumors or risk factors for testicular tumors.

Outcomes for adults with soft tissue sarcoma are better when managed at referral centers. Care guidelines advise for 5 main criteria: 1-Imaging before biopsy; 2-Tumor biopsy before surgery; 3-Multidiscipinary team discussion (MTD) before biopsy; 4-Biopsy in "expert centers"; 5-Somatic molecular biology feasible. The aim is to describe and assess the prognostic impact of initial management of STS according to the type of referring centers and the number of optimal criteria.Monocentric retrospective analysis of the management of 127 youths (0-25 years) with localized STS treated from 2006 to 2015.Median age at diagnosis was 9.6 years (range: 025). Overall, only 41% patients had 5/5, 28% 3-4, 31% ≤2. No adequate imaging was performed before surgery/biopsy for 18% patients, no biopsy before treatment for 29%. Patients referred by "expert centers" had higher compliance to guidelines (P = 0.025). Upfront surgery was performed in 59/127 patients. Immediate re-operation was inversely related to the number of criteria (0% when 5 criteria vs. 14% for 3-4, 46% if ≤ 2; P 0.001). For malignant tumors, outcome was better when 5 criteria were reached: 5 year EFS 90.8% (81.4-100.0%) vs. 71.6 for (60.4-84.9%; ≤4 criteria; p = 0.033), OS 93.6% (85.5-100%) vs. 79.5% (68.9-91.8%; p = 0.11), and LRFFS 90.6% (81.0-100.0) vs. 73.1% (62.0-86.3%; p = 0.047).Less than half of the youths with STS are initially managed according to international guidelines, highlighting the need for better information about optimal management. These results plead for immediate management in reference centers to reduce initial burden of therapy.

Purpose: To investigate the prevalence and magnetic resonance imaging (MRI) phenotype of retinoblastoma-associated orbital cellulitis. Additionally, this study aimed to identify postlaminar optic nerve enhancement (PLONE) patterns differentiating between inflammation and tumor invasion. Design: A monocenter cohort study assessed the prevalence of orbital cellulitis features on MRI in retinoblastoma patients. A multicenter case–control study compared MRI features of the retinoblastoma-associated orbital cellulitis cases with retinoblastoma controls. Participants: A consecutive retinoblastoma patient cohort of 236 patients (311 eyes) was retrospectively investigated. Subsequently, 30 retinoblastoma cases with orbital cellulitis were compared with 30 matched retinoblastoma controls without cellulitis. Methods: In the cohort study, retinoblastoma MRI scans were scored on presence of inflammatory features. In the case–control study, MRI scans were scored on intraocular features and PLONE patterns. Postlaminar enhancement patterns were compared with histopathologic assessment of postlaminar tumor invasion. Interreader agreement was assessed, and exact tests with Bonferroni correction were adopted for statistical comparisons. Main Outcome Measures: Prevalence of retinoblastoma-associated orbital cellulitis on MRI was calculated. Frequency of intraocular MRI features was compared between cases and controls. Sensitivity and specificity of postlaminar optic nerve patterns for detection of postlaminar tumor invasion were assessed. Results: The MRI prevalence of retinoblastoma-associated orbital cellulitis was 6.8% (16/236). Retinoblastoma with orbital cellulitis showed significantly more tumor necrosis, uveal abnormalities (inflammation, hemorrhage, and necrosis), lens luxation (all P < 0.001), and a larger eye size (P = 0.012). The inflammatory pattern of optic nerve enhancement (strong enhancement similar to adjacent choroid) was solely found in orbital cellulitis cases, of which none (0/16) showed tumor invasion on histopathology. Invasive pattern enhancement was found in both cases and controls, of which 50% (5/10) showed tumor invasion on histopathology. Considering these different enhancement patterns suggestive for either inflammation or tumor invasion increased specificity for detection of postlaminar tumor invasion in orbital cellulitis cases from 32% (95% confidence interval [CI], 16–52) to 89% (95% CI, 72–98). Conclusions: Retinoblastoma cases presenting with orbital cellulitis show MRI findings of a larger eye size, extensive tumor necrosis, uveal abnormalities, and lens luxation. Magnetic resonance imaging contrast-enhancement patterns within the postlaminar optic nerve can differentiate between tumor invasion and inflammatory changes.

BCOR-ITD tumours form an emerging family of aggressive entities with an internal tandem duplication (ITD) in the last exon of the BCOR gene. The family includes cerebral tumours, termed central nervous system BCOR-ITD (CNS BCOR-ITD), and sarcomatous types described in the kidney as clear cell sarcoma of the kidney (CCSK), in the endometrium as high-grade endometrial stromal sarcoma, and in the bone and soft tissue as undifferentiated round cell sarcoma or primitive myxoid mesenchymal tumour of infancy. Based on a series of 33 retrospective cases, including 10 CNS BCOR-ITD and 23 BCOR-ITD sarcomas, we interrogated the homogeneity of the entity regarding clinical, radiological, and histopathological findings, and molecular signatures. Whole-transcriptomic sequencing and DNA methylation profiling were used for unsupervised clustering. BCOR-ITD tumours mostly affected young children with a median age at diagnosis of 2.1 years (range 0-62.4). Median overall survival was 3.9 years and progression-free survival was 1.4 years. This dismal prognosis is shared among tumours in all locations except CCSK. Histopathological review revealed marked differences between CNS BCOR-ITD and BCOR-ITD sarcomas. These two groups were consistently segregated by unsupervised clustering of expression (n = 22) and DNA methylation (n = 21) data. Proximity between the two groups may result from common somatic changes within key pathways directly related to the novel activity of the ITD itself. Conversely, comparison of gene signatures with single-cell RNA-Seq atlases suggests that the distinction between BCOR-ITD sarcomas and CNS BCOR-ITD may result from differences in cells of origin.

Infantile fibrosarcoma (IFS) is a rare nonrhabdomyosarcoma soft tissue tumor and accounts for less than 1% of childhood cancers. Forty per cent are present at birth and only 10% of IFS occurs in the abdomen. Our case of neonatal fibrosarcoma presented as a distal small bowel stenosis complicated with meconium peritonitis. The diagnosis was by histology of the surgical resection. The diagnosis of IFS is challenging as there are no specific features of IFS on imaging. Any unexpected solid lesion should raise the suspicion of complicated bowel tumoral lesion. If a neoplastic lesion is suspected extensive, surgery may be postponed until the final diagnosis is made.

NUT carcinoma (NC), defined by the presence of the NUTM1 rearrangement, is an aggressive tumour associated with poor prognosis. This rare cancer is underdiagnosed and difficult to treat.The primary objective of this review is to describe the clinical, radiological and laboratory features of NC in young patients. The secondary objective is to propose a consensual strategy for the French very Rare Tumour group (FRACTURE group).NUT-specific antibody immunostaining in cases of undifferentiated or poorly differentiated carcinoma may demonstrate the specific NUT gene rearrangement. NCs are frequently advanced stage at diagnosis and the outcome remains poor despite a global strategy that generally includes conventional combination chemotherapy with wide local therapy (surgery, radiotherapy). Chemosensitivity is frequently only transient.Recent data have shown that new targeted drugs (histone deacetylase and bromodomain and extra-terminal protein inhibitors) are promising, but their role has yet to be evaluated in NC. Centralized data review is necessary to improve our knowledge of paediatric NC. We propose a multimodal strategy based on published data and their personal experience.

BCOR-ITD tumours form an emerging family of aggressive entities with an internal tandem duplication (ITD) in the last exon of the BCOR gene. The family includes cerebral tumours, termed central nervous system BCOR-ITD (CNS BCOR-ITD), and sarcomatous types described in the kidney as clear cell sarcoma of the kidney (CCSK), in the endometrium as high-grade endometrial stromal sarcoma (HG-ESS), in bone, and in soft tissue as undifferentiated round cell sarcoma (URCS) or primitive myxoid mesenchymal tumour of infancy (PMMTI). Based on a series of 33 retrospective cases, including 10 CNS BCOR-ITD and 23 BCOR-ITD sarcomas, we interrogated the homogeneity of the entity regarding clinical, radiological and histopathological findings, and molecular signatures. Whole transcriptomic sequencing and DNA methylation profiling were used for unsupervised clustering. Histopathological review revealed marked differences between CNS BCOR-ITD and BCOR-ITD sarcomas. These two groups were consistently segregated by unsupervised clustering of expression (n=22) and DNA methylation (n=21) data. Proximity between the two groups may result from common somatic changes within key pathways directly related to the novel activity of the ITD itself. Conversely, comparison of gene signatures with single-cell RNAseq atlases suggests that the distinction between BCOR-ITD sarcomas and CNS BCOR-ITD may result from differences in cells of origin.

VGLL2-rearranged rhabdomyosarcomas (RMS) are rare low-grade tumors with only favorable outcomes reported to date. We describe 4 patients with VGLL2-rearranged RMS confirmed by molecular studies, who experienced local progression and distant metastases, including 2 with fatal outcomes. Tumors were diagnosed at birth (n=3) or at 12 months of age (n=1), and were all localized at initial diagnosis, but unresectable and therefore managed with chemotherapy and surveillance. Metastatic progression occurred from 1 to 8 years from diagnosis (median, 3.5 y). Three patients experienced multimetastatic spread and one showed an isolated adrenal metastasis. At initial diagnosis, 3 tumors displaying bland morphology were misdiagnosed as fibromatosis or infantile fibrosarcoma and initially managed as such, while 1 was a high-grade sarcoma. At relapse, 3 tumors showed high-grade morphology, while 1 retained a low-grade phenotype. Low-grade primary tumors showed only very focal positivity for desmin, myogenin, and/or MyoD1, while high-grade tumors were heterogenously or diffusely positive. Whole-exome sequencing, performed on primary and relapse samples for 3 patients, showed increased genomic instability and additional genomic alterations (eg, TP53, CDKN2A/B, FGFR4) at relapse, but no recurrent events. RNA sequencing confirmed that high-grade tumors retained VGLL2 fusion transcripts and transcriptomic profiles consistent with VGLL2-rearranged RMS. High-grade samples showed a high expression of genes encoding cell cycle proteins, desmin, and some developmental factors. These 4 cases with distinct medical history imply the importance of complete surgical resection, and suggest that RMS-type chemotherapy should be considered in unresectable cases, given the risk of high-grade transformation. They also emphasize the importance of correct initial diagnosis.

Retinoblastoma mimickers, or pseudoretinoblastoma, are conditions that show similarities with the pediatric cancer retinoblastoma. However, false-positive retinoblastoma diagnosis can cause mistreatment, while false-negative diagnosis can cause life-threatening treatment delay. The purpose of this study is to identify the MR imaging features that best differentiate between retinoblastoma and the most common pseudoretinoblastoma diagnoses: Coats&rsquo, disease and persistent fetal vasculature (PFV). Here, six expert radiologists performed retrospective assessments (blinded for diagnosis) of MR images of patients with a final diagnosis based on histopathology or clinical follow-up. Associations between 20 predefined imaging features and diagnosis were assessed with exact tests corrected for multiple hypothesis testing. Sixty-six patients were included, of which 33 (50%) were retinoblastoma and 33 (50%) pseudoretinoblastoma patients. A larger eye size, vitreous seeding, and sharp-V-shaped retinal detachment were almost exclusively found in retinoblastoma (p &lt, 0.001&ndash, 0.022, specificity 93&ndash, 97%). Features that were almost exclusively found in pseudoretinoblastoma included smaller eye size, ciliary/lens deformations, optic nerve atrophy, a central stalk between optic disc and lens, Y-shaped retinal detachment, and absence of calcifications (p &lt, 0.022, specificity 91&ndash, 100%). Additionally, three newly identified imaging features were exclusively present in pseudoretinoblastoma: intraretinal macrocysts (p &lt, 0.001, 38% [9/24] in Coats&rsquo, disease and 20% [2/10] in PFV), contrast enhancement outside the solid lesion (p &lt, 0.001, 30% [7/23] in Coats&rsquo, disease and 57% [4/7] in PFV), and enhancing subfoveal nodules (38% [9/24] in Coats&rsquo, disease). An assessment strategy was proposed for MR imaging differentiation between retinoblastoma and pseudoretinoblastoma, including three newly identified differentiating MR imaging features.

International audience; Soft tissue sarcomas in children are rare tumor, representing around 6 to 7% of children cancer. They spread mostly sporadically (90%) and therefore are rarely associated to an underlying constitutional genetic disease (10%). About half of those sarcomas are rhabdomyosarcomas and the others are a very heterogenous histologic group with various bio-pathologies and prognosis. Clinical presentation is mainly a soft tissue lump often difficult to distinguish from more frequent benign causes (malformative, infectious, benign, or pseudotumor). Inappropriate initial diagnosis work-up has a strong impact on soft tissue sarcomas' prognosis. Adapted complementary investigations (first ultrasound and MRI) are important to compile arguments for a malign origin and to indicate a biopsy. However, predictive value of imaging exams still remains imperfect, and histological analysis by percutaneous image-guided biopsy and sometimes by surgical biopsy is often necessary. Authors realize an update on optimal diagnostic pathway including molecular tests in presence of a soft tissue mass in a child.

The esthesioneuroblastoma (ENB) is characterized as a rare malignant sinonasal tumor of neuroectodermal origin. Its starting point is the olfactory epithelium located in the upper part of the nasal cavities. Different nomenclatures have been proposed, but the most common are "esthesioneuroblastoma" and "olfactory neuroblastoma". ENBs have a bimodal distribution and mainly occur in teenagers, young adults and people aged 50-60. It is a very rare tumor in pediatrics since only around 100 cases have been reported so far. Within ENBs, we can distinguish tumors with different biological behavior ranging from localized forms with slow evolution to aggressive and metastatic forms at onset. In addition, precisely diagnosing undifferentiated tumors and distinguishing them from other etiologies of sinonasal tumors are sometime difficult. Added to its very low incidence, these characteristics make the study of ENB complicated. The standard treatment currently includes broad surgery followed by radiation therapy in localized resectable tumors. Neoadjuvant chemotherapy is indicated in large unresectable tumors and in metastatic forms. However, in certain indications, such as high-grade operable tumors, the role of perioperative chemotherapy remains to be defined. The objective of this analysis is to detail current knowledge regarding ENBs' epidemiological, biological, clinical and radiological characteristics as well as how to manage ENB in young patients.

Soft tissue sarcomas in children are rare tumor, representing around 6 to 7% of children cancer. They spread mostly sporadically (90%) and therefore are rarely associated to an underlying constitutional genetic disease (10%). About half of those sarcomas are rhabdomyosarcomas and the others are a very heterogenous histologic group with various bio-pathologies and prognosis. Clinical presentation is mainly a soft tissue lump often difficult to distinguish from more frequent benign causes (malformative, infectious, benign, or pseudotumor). Inappropriate initial diagnosis work-up has a strong impact on soft tissue sarcomas' prognosis. Adapted complementary investigations (first ultrasound and MRI) are important to compile arguments for a malign origin and to indicate a biopsy. However, predictive value of imaging exams still remains imperfect, and histological analysis by percutaneous image-guided biopsy and sometimes by surgical biopsy is often necessary. Authors realize an update on optimal diagnostic pathway including molecular tests in presence of a soft tissue mass in a child.

Ninety percent of childhood renal tumors are Wilms tumors (nephroblastoma). While the Children's Oncology Group (COG) recommends primary surgery, the International Society of Paediatric Oncology (SIOP) recommends neoadjuvant chemotherapy, which can be initiated without histological confirmation if the presentation is typical for Wilms tumor. This review article describes the clinical, biological and radiologic criteria used by the SIOP community to consider diagnostic biopsy, i.e. when the renal origin is doubtful, when a pseudotumor is suspected or when a non-Wilms histology may be anticipated.

In anterior pituitary deficiency, patients with non visible pituitary stalk have more often multiple deficiencies and persistent deficiency than patients with visible pituitary stalk. To compare the diagnostic value of a high-resolution heavily T2-weighted sequence to 1.5-mm-thick unenhanced and contrast-enhanced sagittal T1-weighted sequences to assess the presence of the pituitary stalk in children with ectopic posterior pituitary gland. We retrospectively evaluated the MRI data of 14 children diagnosed with ectopic posterior pituitary gland between 2010 and 2014. We evaluated the presence of a pituitary stalk using a sagittal high-resolution heavily T2-weighted sequence and a 1.5-mm sagittal T1-weighted turbo spin-echo sequence before and after contrast medium administration. A pituitary stalk was present on at least one of the sequences in 10 of the 14 children (71%). T2-weighted sequence depicted the pituitary stalk in all 10 children, whereas the 1.5-mm-thick T1-weighted sequence depicted 2/10 (20%) before contrast injection and 8/10 (80%) after contrast injection (P=0.007). Compared with 1.5-mm-thick contrast-enhanced T1-weighted sequences, high-resolution heavily T2-weighted sequence demonstrates better sensitivity in detecting the pituitary stalk in children with ectopic posterior pituitary gland, suggesting that contrast injection is unnecessary to assess the presence of a pituitary stalk in this setting.

The standard procedure to study temporal encoding of sound waveforms in the auditory system has been Fourier analysis of responses to periodic stimuli. We introduce a new metric – correlation index (CI) – which is based on a simple counting of spike coincidences. It can be used for responses to aperiodic stimuli and does not require knowledge of the stimulus. Moreover, the basic procedure of comparing spiketimes in spiketrains is more physiological than currently used methods for temporal analysis. The CI is the peak value of the normalized shuffled autocorrelogram (SAC), which provides a quantitative summary of temporal structure in the neural response to arbitrary stimuli. We illustrate the CI and SACs by comparing temporal coding in the auditory nerve and output fibers of the cochlear nucleus.