ALK-rearranged, CD34-positive spindle cell neoplasms resembling dermatofibrosarcoma protuberans: a study of seven cases.

AIMS: The majority of dermatofibrosarcoma protuberans (DFSP) harbour PDGFB or PDGFD rearrangements. We encountered ALK expression/rearrangement in a PDGFB/D-negative CD34-positive spindle cell neoplasm with features similar to DFSP, prompting evaluation of ALK-rearrangements in DFSP and plaque-like CD34-positive dermal fibroma (P-LDF). METHODS AND RESULTS: We searched the archives of academic institutions for cases previously coded as DFSP and P-LDF. NGS-naïve or PDGFB-negative DFSP were screened for ALK (clone D5F3) expression by immunohistochemistry. NGS or ALK FISH was performed on ALK-positive cases. Methylome profiling studies were performed and compared with conventional DFSP. One case of "DFSP" and two "P-LDF" with ALK expression were identified from the archives, while four cases were detected prospectively. These seven cases (6F:1M; 8 months to 76 years) arose in the dermis of the arm (two), scalp, eyelid, thigh, abdomen, and shoulder and ranged from 0.4 to 4.2 cm. Tumours were composed of spindled cells and displayed a storiform growth pattern. Cytologic atypia was absent, and mitotic figures were scarce (0-2/10 HPFs, high power fields). The lesional cells were diffusely positive for CD34 and ALK and negative for S100 protein. By NGS (n = 5), ALK fusion partners included DCTN1 (2), PLEKHH2, and CLIP2 in DFSP-like cases and FLNA in P-LDF-like lesions. ALK FISH was positive in one (of two) cases previously labelled P-LDF. Methylome profiling of two (of three) ALK-rearranged DFSP-like tumours showed clustering with conventional DFSP in the UMAP dimension reduction plot. To date, no tumour has recurred (n = 2; 26, 27 months). CONCLUSION: We describe a cohort of novel ALK-rearranged tumours with morphologic features similar to DFSP.

Combined utility of p16 and BRAF V600E in the evaluation of spitzoid tumors: Superiority to PRAME and correlation with FISH.

BACKGROUND: Spitzoid melanocytic neoplasms are diagnostically challenging; criteria for malignancy continue to evolve. The ability to predict chromosomal abnormalities with immunohistochemistry (IHC) could help select cases requiring chromosomal evaluation. METHODS: Fluorescence in situ hybridization (FISH)-tested spitzoid neoplasms at our institution (2013-2021) were reviewed. p16, BRAF V600E, and preferentially expressed antigen in melanoma (PRAME) IHC results were correlated with FISH. RESULTS: A total of 174 cases (1.9F:1M, median age 28 years; range, 5 months-74 years) were included; final diagnoses: Spitz nevus (11%), atypical Spitz tumor (47%), spitzoid dysplastic nevus (9%), and spitzoid melanoma (32%). Sixty (34%) were FISH positive, most commonly with absolute 6p25 gain (RREB1 > 2). Dermal mitotic count was the only clinicopathologic predictor of FISH. Among IHC-stained cases, p16 was lost in 55 of 134 cases (41%); loss correlated with FISH positive (p < 0.001, Fisher exact test). BRAF V600E (14/88, 16%) and PRAME (15/56, 27%) expression did not correlate with FISH alone (p = 0.242 and p = 0.359, respectively, Fisher exact test). When examined together, however, p16-retained/BRAF V600E-negative lesions had low FISH-positive rates (5/37, 14%; 4/37, 11% not counting isolated MYB loss); all other marker combinations had high rates (56%-75% of cases; p < 0.001). CONCLUSIONS: p16/BRAF V600E IHC predicts FISH results. "Low-risk" lesions (p16+ /BRAF V600E- ) uncommonly have meaningful FISH abnormalities (11%). PRAME may have limited utility in this setting.

Addendum: Technical standards and guidelines: Molecular genetic testing for ultra-rare disorders.

This document was retired by the American College of Medical Genetics and Genomics (ACMG) Board of Directors as of May 20, 2019 with the following addendum.

EWSR1-SMAD3 rearranged fibroblastic tumor: Case series and review.

We report the largest series to date (N = 6) of EWSR1-SMAD3 rearranged fibroblastic tumor. Initially described in 2018, the tumor features a marked female predominance (F:M, 5:1, mean age 44-years, median age 45.5 years; range 27-57), with most cases (5/6, 83%) arising in acral locations (4 on foot/toe, 1 on hand). One case presented on the lower extremity. The lesions presented as nodules and were composed of short, variably cellular, intersecting fascicles of uniform spindled cells in a collagenous to myxoid stroma. In four cases, the tumor abutted the epidermis without a grenz zone. In one case, there was an abrupt transition to a central, acellular hyalinized area. Two other cases had admixed smaller collagenous areas, reminiscent of collagen rosettes. One had a concentric arrangement of tumor cells around blood vessels. Mitotic activity was low (<1/10 HPFs). All were positive for ERG by immunohistochemistry and negative for CD34 (6/6). An EWSR1-SMAD3 fusion was identified in three cases tested by next-generation sequencing (3/3). Rearrangement of EWSR1 by fluorescence in situ hybridization was showed in 1/1 case. Our series reaffirms prior findings and expands the known histopathologic spectrum of this emerging entity.

CFTR variant testing: a technical standard of the American College of Medical Genetics and Genomics (ACMG).

Pathogenic variants in the CFTR gene are causative of classic cystic fibrosis (CF) as well as some nonclassic CF phenotypes. In 2001, CF became the first target of pan-ethnic universal carrier screening by molecular methods. The American College of Medical Genetics and Genomics (ACMG) recommended a core panel of 23 disease-causing variants as the minimal set to be included in pan-ethnic carrier screening of individuals with no family history of the disease, and these variants were usually assessed using targeted methods. The original recommendation also left open the option for laboratories to offer expanded CFTR variant panels; however, at the time, expanded CFTR variant panels were met with some controversy on the basis of the available technologies and the limited phenotypic knowledge of rare variants. Both of those aspects have now evolved, prompting this update of the ACMG technical standards for CFTR variant testing.

Uterine Inflammatory Myofibroblastic Tumor Showing an Atypical ALK Signal Pattern by FISH and DES-ALK Fusion by RNA Sequencing: A Case Report.

Inflammatory myofibroblastic tumors (IMTs) are spindle cell neoplasms of intermediate (borderline) biologic potential with tendency for local recurrence but low risk of metastasis. They affect children more than adults. The most common sites of involvement are the lung, soft tissue, peritoneum, bladder, and less commonly the gynecologic tract. IMTs are characterized by spindle to epithelioid cells with myofibroblastic differentiation, some degree of smooth muscle differentiation, myxoid stroma and usually associated with brisk lymphoplasmacytic infiltrates. In about half of the cases, IMTs are associated with rearrangements of the anaplastic lymphoma kinase (ALK) gene located at chromosome 2p23. The ALK rearrangement can be detected by immunohistochemistry for ALK protein expression (mostly cytoplasmic with or without perinuclear accentuation) or by fluorescent in situ hybridization (FISH) using dual-color break-apart probes for which the typical pattern is seen as split 3' end (red) and 5' end (green) probe signals in addition to single normal, unsplit red-green signal pair (yellow). Herein we describe a case of uterine IMT initially misdiagnosed intraoperatively as leiomyoma which showed sparse lymphocytic infiltrates, positive ALK expression by immunohistochemistry, a predominantly atypical FISH signal pattern (1 yellow and 1 red signal only) and few typical signal patterns (1 yellow, 1 red, and 1 green signal) in a smaller population of tumor cells. The RNA sequencing showed a recently described DES-ALK fusion transcript in the tumor cells, suggesting an intrachromosomal inversion and deletion as the likely underlying mechanism for the atypical FISH pattern. Familiarity with the unusual morphology and atypical FISH pattern is crucial given that this tumor has an activating ALK rearrangement and may benefit from targeted tyrosine kinase inhibitors in the future.

Assessing the Clinical Utility of SNP Microarray for Prader-Willi Syndrome due to Uniparental Disomy.

Maternal uniparental disomy (UPD) 15 is one of the molecular causes of Prader-Willi syndrome (PWS), a multisystem disorder which presents with neonatal hypotonia and feeding difficulty. Current diagnostic algorithms differ regarding the use of SNP microarray to detect PWS. We retrospectively examined the frequency with which SNP microarray could identify regions of homozygosity (ROH) in patients with PWS. We determined that 7/12 (58%) patients with previously confirmed PWS by methylation analysis and microsatellite-positive UPD studies had ROH (>10 Mb) by SNP microarray. Additional assessment of 5,000 clinical microarrays, performed from 2013 to present, determined that only a single case of ROH for chromosome 15 was not caused by an imprinting disorder or identity by descent. We observed that ROH for chromosome 15 is rarely incidental and strongly associated with hypotonic infants having features of PWS. Although UPD microsatellite studies remain essential to definitively establish the presence of UPD, SNP microarray has important utility in the timely diagnostic algorithm for PWS.

Partial tetrasomy 11q resulting from an intrachromosomal triplication of a 22 Mb region of chromosome 11.

Intrachromosomal triplications are complex chromosomal rearrangements which arise during meiosis or mitosis and lead to a tetrasomic dose of the affected genomic regions. We describe a female patient harboring an intrachromosomal triplication who presented to the Genetics clinic with dysmorphic features, including telecanthus, flat facial profile, and prognathism, short stature, widely spaced nipples, multiple allergy complaints, loose bowel movements, and mild speech delay. Microarray analysis showed a copy number gain of a 22.37 Mb region of chromosome 11 between bands 11q14.1 and 11q22.1. This region contains 95 genes and seven microRNAs, none of which have been implicated in a disease resulting from increased gene dosage. FISH analysis using a probe targeted to the middle of the segment of the copy number gain yielded a pattern indicative of a tetrasomy via an intrachromosomal triplication, with three signals on the long arm of one homologue of chromosome 11 and the fourth on the other homologue. Subsequent FISH analysis showed that the middle triplicated fragment was positioned in an inverted orientation relative to the outer fragments. To investigate the mechanism by which the intrachromosomal triplication occurred, SNP microarray analysis was performed. These results were consistent with the presence of multiple haplotypes in the tetrasomic region and suggest that the intrachromosomal triplication in our patient arose in one parent during meiosis. © 2017 Wiley Periodicals, Inc.

Histology, fusion status, and outcome in metastatic rhabdomyosarcoma: A report from the Children's Oncology Group.

BACKGROUND: Distinguishing alveolar rhabdomyosarcoma (ARMS) from embryonal rhabdomyosarcoma (ERMS) has historically been of prognostic and therapeutic importance. However, classification has been complicated by shifting histologic criteria required for an ARMS diagnosis. Children's Oncology Group (COG) studies after IRS-IV, which included the height of this diagnostic shift, showed both an increased number of ARMS and an increase in the proportion of fusion-negative ARMS. Following diagnostic standardization and histologic re-review of ARMS cases enrolled during this era, analysis of low-risk (D9602) and intermediate-risk (D9803) rhabdomyosarcoma (RMS) studies showed that fusion status rather than histology best predicts prognosis for patients with RMS. This analysis remains to be completed for patients with high-risk RMS. PROCEDURE: We re-reviewed cases on high-risk COG studies D9802 and ARST0431 with an enrollment diagnosis of ARMS. We compared the event-free survival (EFS) and overall survival by histology, PAX-FOXO1 fusion, and clinical risk factors (Oberlin score) for patients with metastatic RMS using the log-rank test. RESULTS: Histology re-review resulted in reclassification as ERMS for 12% of D9802 cases and 5% of ARST0431 cases. Fusion-negative RMS had a superior EFS to fusion-positive RMS; however, poorer outcome for metastatic RMS was most related to clinical risk factors including age, primary site, and number of metastatic sites. CONCLUSIONS: In contrast to low- or intermediate-risk RMS, in metastatic RMS, clinical risk factors have the most impact on patient outcome. PAX-FOXO1 fusion is more common in patients with a high Oberlin score, but fusion status is not an independent biomarker of prognosis.

Assessment of 2q23.1 microdeletion syndrome implicates MBD5 as a single causal locus of intellectual disability, epilepsy, and autism spectrum disorder.

Persons with neurodevelopmental disorders or autism spectrum disorder (ASD) often harbor chromosomal microdeletions, yet the individual genetic contributors within these regions have not been systematically evaluated. We established a consortium of clinical diagnostic and research laboratories to accumulate a large cohort with genetic alterations of chromosomal region 2q23.1 and acquired 65 subjects with microdeletion or translocation. We sequenced translocation breakpoints; aligned microdeletions to determine the critical region; assessed effects on mRNA expression; and examined medical records, photos, and clinical evaluations. We identified a single gene, methyl-CpG-binding domain 5 (MBD5), as the only locus that defined the critical region. Partial or complete deletion of MBD5 was associated with haploinsufficiency of mRNA expression, intellectual disability, epilepsy, and autistic features. Fourteen alterations, including partial deletions of noncoding regions not typically captured or considered pathogenic by current diagnostic screening, disrupted MBD5 alone. Expression profiles and clinical characteristics were largely indistinguishable between MBD5-specific alteration and deletion of the entire 2q23.1 interval. No copy-number alterations of MBD5 were observed in 7878 controls, suggesting MBD5 alterations are highly penetrant. We surveyed MBD5 coding variations among 747 ASD subjects compared to 2043 non-ASD subjects analyzed by whole-exome sequencing and detected an association with a highly conserved methyl-CpG-binding domain missense variant, p.79Gly>Glu (c.236G>A) (p = 0.012). These results suggest that genetic alterations of MBD5 cause features of 2q23.1 microdeletion syndrome and that this epigenetic regulator significantly contributes to ASD risk, warranting further consideration in research and clinical diagnostic screening and highlighting the importance of chromatin remodeling in the etiology of these complex disorders.

Conventional Cytogenetic Analysis of Constitutional Abnormalities: A 20-Year Review of Proficiency Test Results From the College of American Pathologists/American College of Medical Genetics and Genomics Cytogenetics Committee.

CONTEXT.­: The joint College of American Pathologists/American College of Medical Genetics and Genomics Cytogenetics Committee works to ensure competency and proficiency of clinical cytogenetics testing laboratories through proficiency testing programs for various clinical tests offered by such laboratories, including the evaluation of constitutional abnormalities. OBJECTIVE.­: To review and analyze 20 years of constitutional chromosome analysis proficiency testing results (2003-2022), primarily utilizing G-banded karyograms. DESIGN.­: A retrospective review of results from 2003 through 2022 was performed, identifying challenges addressing constitutional disorders. The chromosomal abnormalities and overall performance were evaluated. RESULTS.­: A total of 184 cases from 161 proficiency testing challenges were administered from 2003 through 2022. Challenges consisted of metaphase images and accompanying clinical history for evaluation of numerical and/or structural abnormalities. Of the 184 cases, only 2 (1%) failed to reach an 80% grading consensus for recognition of the abnormality. Both cases illustrated the limitations of correctly characterizing some chromosomal abnormalities, including recombinant chromosomal abnormalities and isochromosome identification. In addition, 2 cases failed to reach a consensus for nomenclature reporting: 1 with an isochromosome and another with a duplication. CONCLUSIONS.­: This 20-year review illustrates the high rate of competency and proficiency of cytogenetic laboratories in the correct identification of constitutional chromosome abnormalities.

A Single-Arm Phase 2 Trial of Trametinib in Patients with Locally Advanced or Metastatic Epithelioid Hemangioendothelioma.

PURPOSE: Epithelioid hemangioendothelioma (EHE) is a rare vascular cancer with pathogenic TAZ-CAMTA1 (calmodulinbinding transcription activator 1) operating as an oncogenic driver through activation of the MAPK pathway. Trametinib is an inhibitor of MEK, a critical kinase in the MAPK pathway. We sought to evaluate the effect of trametinib in patients with EHE. PATIENTS AND METHODS: A phase 2 trial of trametinib was conducted in patients with locally advanced or metastatic EHE. Eligibility requirements included evidence of tumor progression or presence of EHE-related pain requiring opiates for management before enrollment. The primary endpoint was objective response rate (ORR) as per RECIST1.1 in cases with TAZ- CAMTA1 confirmed by fusion-FISH. Secondary objectives were to estimate ORR for all patients, median progression-free survival (PFS), 2-year overall survival (OS) rate, patient safety, and change in patient-reported global health and pain scores per PROMIS questionnaires. RESULTS: 44 patients enrolled and 42 started trametinib. TAZ- CAMTA1 was detected in 27 tumor samples. TheORRwas 3.7%[95% confidence interval (CI), 0.094-19.0], median PFS was 10.4 months (95%CI, 7.1-NA), and 2-year OS rate was 33.3%(95%CI, 19.1-58.2) in the target population. Median pain intensity and interference scores improved significantly after 4 weeks of trametinib in patients using opiates. Common adverse events related to trametinib were rash, fatigue, nausea/vomiting, diarrhea/constipation, alopecia, and edema; one grade 5 ARDS/pneumonitis was related to trametinib. CONCLUSIONS: Trametinib was associated with reduction in EHE-related pain and median PFS of more than 6 months, providing palliative benefit in patients with advanced EHE, but the trial did not meet the ORR goal. See related commentary by Van Tine and Haarberg, p. 4552.

Identification of a recurrent microdeletion at 17q23.1q23.2 flanked by segmental duplications associated with heart defects and limb abnormalities.

Segmental duplications, which comprise approximately 5%-10% of the human genome, are known to mediate medically relevant deletions, duplications, and inversions through nonallelic homologous recombination (NAHR) and have been suggested to be hot spots in chromosome evolution and human genomic instability. We report seven individuals with microdeletions at 17q23.1q23.2, identified by microarray-based comparative genomic hybridization (aCGH). Six of the seven deletions are approximately 2.2 Mb in size and flanked by large segmental duplications of >98% sequence identity and in the same orientation. One of the deletions is approximately 2.8 Mb in size and is flanked on the distal side by a segmental duplication, whereas the proximal breakpoint falls between segmental duplications. These characteristics suggest that NAHR mediated six out of seven of these rearrangements. These individuals have common features, including mild to moderate developmental delay (particularly speech delay), microcephaly, postnatal growth retardation, heart defects, and hand, foot, and limb abnormalities. Although all individuals had at least mild dysmorphic facial features, there was no characteristic constellation of features that would elicit clinical suspicion of a specific disorder. The identification of common clinical features suggests that microdeletions at 17q23.1q23.2 constitute a novel syndrome. Furthermore, the inclusion in the minimal deletion region of TBX2 and TBX4, transcription factors belonging to a family of genes implicated in a variety of developmental pathways including those of heart and limb, suggests that these genes may play an important role in the phenotype of this emerging syndrome.

Impaired regeneration in LGMD2A supported by increased PAX7-positive satellite cell content and muscle-specific microrna dysregulation.

INTRODUCTION: Recent in vitro studies suggest that CAPN3 deficiency leads initially to accelerated myofiber formation followed by depletion of satellite cells (SC). In normal muscle, up-regulation of miR-1 and miR-206 facilitates transition from proliferating SCs to differentiating myogenic progenitors. METHODS: We examined the histopathological stages, Pax7 SC content, and muscle-specific microRNA expression in biopsy specimens from well-characterized LGMD 2A patients to gain insight into disease pathogenesis. RESULTS: Three distinct stages of pathological changes were identified that represented the continuum of the dystrophic process from prominent inflammation with necrosis and regeneration to prominent fibrosis, which correlated with age and disease duration. Pax7-positive SCs were highest in the fibrotic group and correlated with down-regulation of miR-1, miR-133a, and miR-206. CONCLUSIONS: These observations, and other published reports, are consistent with microRNA dysregulation leading to inability of Pax7-positive SCs to transit from proliferation to differentiation. This results in impaired regeneration and fibrosis.