Kathleen Kaiser-Rogers

Discordant noninvasive prenatal testing results in a patient subsequently diagnosed with metastatic disease

University of North Carolina at Chapel Hill School of Medicine, Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Chapel Hill, NC 27599, USA Verinata Health, Inc., Department of Clinical Affairs, Redwood City, CA, USA University of North Carolina at Chapel Hill School of Medicine, Department of Pathology and Laboratory Medicine, Chapel Hill, NC, USA *Correspondence to: Neeta L. Vora. E-mail: nvora@med.unc.edu

Androgenetic/biparental mosaicism causes placental mesenchymal dysplasia

Background: Placental mesenchymal dysplasia (PMD) is a distinct syndrome of unknown aetiology that is associated with significant fetal morbidity and mortality. Intrauterine growth restriction is common, yet, paradoxically, many of the associated fetuses/newborns have been diagnosed with Beckwith-Wiedemann syndrome (BWS). Methods: We report two cases of PMD with high levels of androgenetic (complete paternal uniparental isodisomy) cells in the placenta and document, in one case, a likely androgenetic contribution to the fetus as well. Results: The same haploid paternal complement found in the androgenetic cells was present in coexisting biparental cells, suggesting origin from a single fertilisation event. Conclusions: Preferential allocation of the normal cells into the trophoblast explains the absence of trophoblast overgrowth, a key feature of this syndrome. Interestingly, the distribution of androgenetic cells appears to differ from that reported for artificially created androgenetic mouse chimeras. Androgenetic mosaicism for the first time provides an aetiology for PMD, and may be a novel mechanism for BWS and unexplained intrauterine growth restriction.

Aortopathy in the 7q11.23 microduplication syndrome

The 7q11.23 microduplication syndrome, caused by the reciprocal duplication of the Williams‐Beuren syndrome deletion region, is a genomic disorder with an emerging clinical phenotype. Dysmorphic features, congenital anomalies, hypotonia, developmental delay highlighted by variable speech delay, and autistic features are characteristic findings. Congenital heart defects, most commonly patent ductus arteriosus, have been reported in a minority of cases. Included in the duplicated region is elastin (ELN), implicated as the cause of supravalvar aortic stenosis in patients with Williams–Beuren syndrome. Here we present a series of eight pediatric patients and one adult with 7q11.23 microduplication syndrome, all of whom had aortic dilation, the opposite vascular phenotype of the typical supravalvar aortic stenosis found in Williams–Beuren syndrome. The ascending aorta was most commonly involved, while dilation was less frequently identified at the aortic root and sinotubular junction. The findings in these patients support a recommendation for cardiovascular surveillance in patients with 7q11.23 microduplication syndrome.

A rational approach to genetic testing for sarcoma.

Diagnosis of sarcoma increasingly relies on identifying genetic defects using modern molecular technologies. Each analytic method has unique advantages and specimen requirements that should be considered when allocating tissue for downstream testing. Karyotype on fresh tissue represents a genome-wide screen of gross chromosomal alterations, whereas fluorescence in situ hybridization and polymerase chain reaction detect specific defects that are characteristic of a given tumor type such as t(11;22) EWSR1-FLI1 in Ewing family tumors, t(X;18) SS18-SSX1 in synovial sarcoma, t(2;13) PAX3-FOXO1A in alveolar rhabdomyosarcoma, and MYCN gene amplification in neuroblastoma. Identifying a clonal genetic defect also provides a tumor marker that could help stage the extent of spread of the neoplasm or monitor the efficacy of therapy. In research laboratories, array-based methods identify genes and biochemical pathways contributing to tumor growth and maintenance, opening avenues for pharmacogenetic tests that predict which therapy is likely to overcome the biochemical defects with minimal toxicity. Array-based discoveries are also spurring validation of smaller test panels that rely on conventional technologies such as immunohistochemistry and reverse transcription polymerase chain reaction. The pathologists expertize is critical in: (1) consulting with clinicians about specimen collection and handling; (2) preserving tissue for immediate testing and for any downstream testing that is indicated once morphology and immunophenotype are known; (3) performing tests that maximize outcome on the basis of the strengths and limitations of each assay in each available specimen type; and (4) conveying results to the rest of the healthcare team using proper gene nomenclature and interpreting the findings in a way that facilitates optimal clinical management.

Structural Chromosome Rearrangements

The subject of structural chromosome rearrangements is an immense one, to which entire catalogs have been devoted. Indeed, there are theoretically an almost infinite number of ways in which chromosomes can reconfigure themselves from the normal 23-pair arrangement with which we are familiar. Although we tend to think of the resulting structural rearrangements in terms of chromosome pathology, some rearrangements are fairly innocuous. In fact, a few such benign rearrangements (such as certain pericentric inversions of chromosome 9) are seen frequently enough to be considered polymorphic variants of no clinical significance.

PTEN deficiency mediates a reciprocal response to IGFI and mTOR inhibition.

Recent evidence implicates the insulin-like growth factor (IGF) pathway in development of Ewing sarcoma, a highly malignant bone and soft-tissue tumor that primarily affects children and young adults. Despite promising results from preclinical studies of therapies that target this pathway, early-phase clinical trials have shown that a significant fraction of patients do not benefit, suggesting that cellular factors determine tumor sensitivity. Using FAIRE-seq, a chromosomal deletion of the PTEN locus in a Ewing sarcoma cell line was identified. In primary tumors, PTEN deficiency was observed in a large subset of cases, although not mediated by large chromosomal deletions. PTEN loss resulted in hyperactivation of the AKT signaling pathway. PTEN rescue led to decreased proliferation, inhibition of colony formation, and increased apoptosis. Strikingly, PTEN loss decreased sensitivity to IGF1R inhibitors but increased responsiveness to temsirolimus, a potent mTOR inhibitor, as marked by induction of autophagy. These results suggest that PTEN is lost in a significant fraction of primary tumors, and this deficiency may have therapeutic consequences by concurrently attenuating responsiveness to IGF1R inhibition while increasing activity of mTOR inhibitors. The identification of PTEN status in the tumors of patients with recurrent disease could help guide the selection of therapies. Implications: PTEN status in Ewing sarcoma affects cellular responses to IGFI and mTOR-directed therapy, thus justifying its consideration as a biomarker in future clinical trials. Mol Cancer Res; 12(11); 1610–20. ©2014 AACR.

Neuroblastoma in a pediatric patient with a microduplication of 2p involving the MYCN locus

Neuroblastoma is the most common solid tumor of infancy, and mutations in several genes have been implicated as playing a role in tumor development. Here, we describe a pediatric patient with a constitutional microduplication of 2p24.3 who developed Stage 4 neuroblastoma at age 11 months. He represents the sixth patient described in the literature with partial trisomy 2p and neuroblastoma. All previous cases had duplication events spanning two genes implicated in neuroblastoma, MYCN and ALK. Our patient is unique because his duplicated region includes the MYCN gene only; the ALK gene is unaffected. These data, combined with the relatively high incidence of neuroblastoma reported in partial trisomy 2p patients, support the notion that MYCN duplication should be added to the growing list of genetic factors associated with an increased risk of neuroblastoma. The mechanism of increased risk is unclear, but the fact that our patient had dramatic amplification of MYCN in his tumor suggests that a germline duplication might predispose to further amplification. Additionally, our patient has several morphologic features common to patients with partial trisomy 2p including high forehead, hypertelorism, postaxial polydactyly, and developmental delay despite having a microduplication spanning approximately 1 Mb and including just three intact genes. This case may therefore help further delineate the genotype–phenotype correlations associated with partial trisomy 2p.

Submicroscopic deletion 9(q34.3) and duplication 19(p13.3): identified by subtelomere specific FISH probes.

Submicroscopic rearrangements involving chromosome ends are responsible for the unexplained mental retardation and multiple congenital anomalies observed in a number of patients. We have studied a patient with mental retardation, significant microcephaly, alopecia universalis, and other anomalies who carries an unbalanced segregant from a cryptic reciprocal translocation involving chromosomes 9 and 19. FISH studies using subtelomere specific probes revealed a derivative chromosome 9 in which the 9q subtelomeric sequence has been replaced by 19p subtelomeric sequence. As a result, the patient has partial monosomy 9q and partial trisomy 19p. The patient inherited the derivative 9 from his father, who carries a cryptic apparently balanced reciprocal translocation involving the terminal regions of 9q and 19p. This case is exceptional in that reports of rearrangements involving distal chromosome 9q and 19p are rare. This study demonstrates the utility of subtelomere specific FISH probes for detecting cyptic subtelomeric rearrangements in patients with idiopathic mental retardation and normal appearing karyotypes.

Karyotypic abnormalities associated with Epstein-Barr virus status in classical Hodgkin lymphoma.

Classical Hodgkin lymphoma (CHL) is morphologically characterized by scattered malignant Hodgkin/Reed-Sternberg (HRS) cells that are far outnumbered by surrounding reactive hematolymphoid cells. Approximately half of all cases of CHL are associated with infection by Epstein-Barr virus (EBV), an oncogenic herpesvirus that expresses a number of proteins thought to contribute to transformation. While a small number of published studies have attempted to identify recurrent cytogenetic abnormalities in CHL, no large case series have explored karyotypic differences between EBV-positive and EBV-negative tumors. Here, we report a two-institution retrospective investigation of cytogenetic features characterizing CHL. In our cohort, cases of EBV-negative CHL were characterized by more complex routine karyotypes than their EBV-positive counterparts (24.6 versus 15.6 independent aberrations per case, P = 0.009). The increased complexity of EBV-negative cases was driven by a number of features suggestive of genomic instability, including a larger number of independent chromosomal breakpoints (P = 0.03) and apparently aneuploid autosomes (P = 0.008). Compelling but nonsignificant trends also suggest a larger modal number and increased marker chromosomes in EBV-negative cases (P = 0.13 and 0.06, respectively). While some of these differences are related to histologic subtype, others appear independent of histology. Finally, a significant subset of EBV-positive tumors has a surprisingly simple karyotype relative to what is normally seen in CHL, an observation suggesting considerable biological and genetic diversity in this disease.

Cell-free DNA testing in a trisomy 21 pregnancy with confined placental mosaicism for a cell line with trisomy for both chromosomes 18 and 21.

NIPT (noninvasive prenatal testing) detected trisomy for two chromosomes. One trisomy reflected the fetal karyotype, and the other resulted from CPM (confined placental mosaicism). This case illustrates that extensive cytogenetic analysis can be required to identify CPM, and that patients should be counseled regarding the possibility of discordant NIPT results.