Clinical and genetic features of rhabdoid tumors of the heart registered with the European Rhabdoid Registry (EU-RHAB)

Current status of DNA methylation profiling in neuro-oncology as a diagnostic support tool: A review

Over the last 2 decades, high throughput genome-wide molecular profiling has revealed characteristic genetic and epigenetic alterations associated with different types of central nervous system (CNS) tumors. DNA methylation profiling has emerged as an important molecular platform for CNS tumor classification with improved diagnostic accuracy and patient risk stratification in comparison to the standard of care histopathological analysis and any single molecular tests. The emergence of DNA methylation arrays have also played a crucial role in refining existing types and the discovery of new tumor types or subtypes. The adoption of methylation data into neuro-oncology has been greatly aided by the development of a freely accessible machine learning-based classifier. In this review, we discuss methylation workflow, address the utility of DNA methylation profiling in CNS tumors in a routine diagnostic setting, and provide an overview of the methylation-based tumor types and new types or subtypes identified with this platform.

Cardiac Rhabdoid Tumor—A Rare Foe—Case Report and Literature Review

Intracardiac masses are unusual findings in infants, and most of them are benign. Nevertheless, they may be associated with a significant degree of hemodynamic instability and/or arrhythmias. Malignant tumors of the heart rarely occur in children. Rhabdoid tumors are aggressive tumors with a dismal prognosis even when diagnosed early. Although rhabdomyomas are common cardiac tumors in infants, they are mostly benign. The most common sites of involvement are the kidneys and central nervous system, but soft tissues, lungs, and ovaries may also be affected. The diagnosis can be challenging, particularly in sites where they do not usually occur. In the present paper, we report the case of a 2-year-old boy diagnosed with cardiac rhabdoid tumor highlighting the importance of molecular studies and recent genetic discoveries with the purpose of improving the management of such cases. The aim of this educational case report and literature review is to raise awareness of cardiac masses in children and to point out diagnostic hints toward a cardiac tumor on various imaging modalities. Given the rarity of all tumors involving the heart and the lack of symptom specificity, a high degree of suspicion is needed to arrive at the correct diagnosis.

Age and DNA methylation subgroup as potential independent risk factors for treatment stratification in children with atypical teratoid/rhabdoid tumors

BACKGROUND

Controversy exists as to what may be defined as standard of care (including markers for stratification) for patients with atypical teratoid/rhabdoid tumors (ATRTs). The European Rhabdoid Registry (EU-RHAB) recruits uniformly treated patients and offers standardized genetic and DNA methylation analyses.

METHODS

Clinical, genetic, and treatment data of 143 patients from 13 European countries were analyzed (2009-2017). Therapy consisted of surgery, anthracycline-based induction, and either radiotherapy or high dose chemotherapy following a consensus among European experts. Fluorescence in situ hybridization, multiplex ligation-dependent probe amplification, and sequencing were employed for assessment of somatic and germline mutations in SWItch/sucrose nonfermentable related, matrix associated, actin dependent regulator of chromatin, subfamily B (SMARCB1). Molecular subgroups (ATRT-SHH, ATRT-TYR, and ATRT-MYC) were determined using DNA methylation arrays, resulting in profiles of 84 tumors.

RESULTS

Median age at diagnosis of 67 girls and 76 boys was 29.5 months. Five-year overall survival (OS) and event-free survival (EFS) were 34.7 ± 4.5% and 30.5 ± 4.2%, respectively. Tumors displayed allelic partial/whole gene deletions (66%; 122/186 alleles) or single nucleotide variants (34%; 64/186 alleles) of SMARCB1. Germline mutations were detected in 26% of ATRTs (30/117). The patient cohort consisted of 47% ATRT-SHH (39/84), 33% ATRT-TYR (28/84), and 20% ATRT-MYC (17/84). Age <1 year, non-TYR signature (ATRT-SHH or -MYC), metastatic or synchronous tumors, germline mutation, incomplete remission, and omission of radiotherapy were negative prognostic factors in univariate analyses (P < 0.05). An adjusted multivariate model identified age <1 year and a non-TYR signature as independent negative predictors of OS: high risk (<1 y + non-TYR; 5-y OS = 0%), intermediate risk (<1 y + ATRT-TYR or ≥1 y + non-TYR; 5-y OS = 32.5 ± 8.7%), and standard risk (≥1 y + ATRT-TYR, 5-y OS = 71.5 ± 12.2%).

CONCLUSIONS

Age and molecular subgroup status are independent risk factors for survival in children with ATRT. Our model warrants validation within future clinical trials.

SMARCB1-deficient Tumors of Childhood: A Practical Guide

The SMARCB1 gene ( INI1, BAF47) is a member of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, involved in the epigenetic regulation of gene transcription. SMARCB1 acts as a tumor suppressor gene, and loss of function of both alleles gives rise to SMARCB1-deficient tumors. The prototypical SMARCB1-deficient tumor is the malignant rhabdoid tumor (MRT) which was first described in the kidney but also occurs in soft tissue, viscera, and the brain (where it is referred to as atypical teratoid rhabdoid tumor or AT/RT). These are overwhelmingly tumors of the very young, and most follow an aggressive and ultimately lethal course. Morphologically, most but not all contain a population of "rhabdoid" cells, which are large cells with abundant cytoplasm, perinuclear spherical inclusions, and eccentric vesicular nuclei with large inclusion-like nucleoli. MRT immunohistochemistry reveals complete loss of SMARCB1 nuclear expression, and molecular analysis confirms biallelic SMARCB1 inactivation in the vast majority. Rare AT/RTs have loss of SMARCA4, another SWI/SNF member, rather than SMARCB1. With the widespread adoption of SMARCB1 immunohistochemistry, an increasing number of SMARCB1-deficient tumors outside of the MRT-AT/RT spectrum have been described. In addition to MRT and AT/RT, pediatric tumors with complete loss of SMARCB1 expression include cribriform neuroepithelial tumor, renal medullary carcinoma, and epithelioid sarcoma. Tumors with variable loss of SMARCB1 expression include subsets of epithelioid malignant peripheral nerve sheath tumor, schwannomas arising in schwannomatosis, subsets of chordomas, myoepithelial carcinomas, and sinonasal carcinomas. Variable and reduced expression of SMARCB1 is characteristic of synovial sarcoma. In this review, the historical background, clinical characteristics, morphology, immunohistochemical features, and molecular genetics most germane to these tumors are summarized. In addition, familial occurrence of these tumors (the rhabdoid tumor predisposition syndrome) is discussed. It is hoped that this review may provide practical guidance to pathologists encountering tumors that have altered expression of SMARCB1.

Rhabdoid tumors: integrating biological insights with clinical success: a report from the SMARCB1 and Rhabdoid Tumor Symposium, Paris, December 12-14, 2013

Malignant rhabdoid tumors (MRTs) of the central nervous system (atypical teratoid, rhabdoid tumor (AT/RT)), kidney (rhabdoid tumor of the kidney (RTK)), and soft tissues all share an aggressive clinical behavior and dismal prognosis. The burden of the intensive treatment required to cure patients is a matter of great concern given the young median age at diagnosis, regardless of tumor location. Thus, a greater understanding of the oncogenic properties of SMARCB1 and the SWI/SNF complex, as well as the clinical aspects of malignant rhabdoid tumors is necessary. Towards this aim, the first international SMARCB1 and rhabdoid tumor symposium was held in Paris, France in December 2013, organized by the collaborative efforts of the Dana-Farber Cancer Institute (Susan Chi), Swabian Children's Cancer Center/EU-RHAB Center (Michael Frühwald) and Curie Institute (Franck Bourdeaut). This workshop of physicians and other scientists fostered the integration of biologic insights towards clinical application in rhabdoid tumors, and other SWI/SNF-related cancers. The following report is a synopsis of the highlights of this meeting.