Citations

Background/Objective: Although most melanocytic lesions are diagnosed as benign or malignant by histopathologic evaluation, with or without the aid of immunohistochemistry, diagnosis may remain uncertain in a minority of cases. Assessment of copy number abnormalities (CNAs) may provide sufficient additional evidence to favor either a benign or malignant diagnosis in both pediatric and adult cases and in melanocytic lesions of various subtypes, including Spitzoid, mucosal, and acral. CNAs are common in melanomas, while they are rare, with few exceptions, in benign lesions. Detection of CNAs by fluorescence in situ hybridization (FISH) and chromosomal microarray (CMA) has been well established for melanocytic lesions, with advantages and disadvantages for each. The objective of this meta-analysis was to evaluate the utility of CNA testing for the diagnosis of melanoma, across subtypes, when a lesion remains ambiguous after histopathologic and immunohistochemical assessment. In addition, the utility of CNAs to determine prognosis in established diagnoses of melanoma was also evaluated. Methods: The Cancer Genomics Consortium Working Group for Melanocytic Lesions reviewed published data from January 1998 through September 2022 of CNAs in melanocytic lesions detected by either FISH or CMA and conducted a meta-analysis of the findings. Results: Specific abnormalities common in primary cutaneous melanomas of various subtypes and uveal melanomas were enumerated. Differences in CNAs found in primary versus metastatic lesions were also determined, and published evidence for prognosis was summarized. Conclusions: The working group established evidence-based recommendations for the use of CNA testing for evaluation of ambiguous melanocytic lesions.

Abstract Isolated trisomy 2 in hematopoietic malignancies is rare, having only been reported in eight cases in the literature. Of these cases, the majority are older male patients (7/8) ranging in age from 64 to 84 years. The underlying hematologic malignancies include: myelodysplastic syndrome (MDS), refractory anemia (RA) subtype; MDS, RA with excess blasts (RAEB-II) subtype; MDS, RAEB in transformation (RAEB-t); chronic myelomonocytic leukemia (CMML-t) in transformation; MDS transformed into AML; acute monoblastic and monocytic leukemia (AMoL; FAB M5); and AML in relapse. The molecular pathogenesis and prognostic significance of isolated trisomy 2 remains unknown due to the small number of reported cases. Herein, we report 11 cases of isolated trisomy 2 in hematologic disorders seen in the Mayo Clinic Cytogenetics laboratory from 1996-2012. The majority of patients were older males (7/11) ranging in age from 63 to 93 years. The underlying bone marrow pathologic diagnoses include: hypercellular bone marrow without diagnostic features of malignancy (cases 1 and 2); MDS, refractory cytopenia with multilineage dysplasia (RCMD) subtype (cases 3 and 4); RAEB-1 (cases 5 and 6); long-standing history of primary myelofibrosis now with 7% bone marrow blasts (case 7); acute myeloid leukemia (AML), not otherwise specified (cases 8 and 9); AML with myelodysplasia-related changes (cases 10 and 11). Trisomy 2 has been suggested to represent an age-related phenomenon as it is seen predominantly in older individuals demonstrating this abnormality. Our data suggests that this could be a possible explanation since all of the eleven cases were ages 63 and over. Based on the limited clinical information in our study, it appears that isolated trisomy 2 harbors little prognostic significance and that, rather, the prognostic significance is driven by the underlying pathologic diagnosis. For example, 3 of the 4 AML cases and the case of PMF with increasing bone marrow blasts survived only 7, 8, 6 weeks and 21 weeks post bone marrow biopsy/cytogenetic evaluation, respectively. Although our study only has two cases that lack diagnostic features of malignancy, one of these cases survived 10 years following the identification of the cytogenetic abnormality. Therefore, trisomy 2 as a sole abnormality should not be considered as definitive evidence for MDS in the absence of diagnostic morphological criteria (similar to trisomy 8 and 20q deletion). Disclosures: No relevant conflicts of interest to declare.

AbstractObjectiveAcute myeloid leukemia (AML) can be subtyped based on recurrent cytogenetic and molecular genetic abnormalities with diagnostic and prognostic significance. Although cytogenetic characterization classically involves conventional chromosome and/or fluorescence in situ hybridization (FISH) assays, limitations of these techniques include poor resolution and the inability to precisely identify breakpoints.MethodWe evaluated whether an NGS‐based methodology that detects structural abnormalities and copy number changes using mate pair sequencing (MPseq) can enhance the diagnostic yield for patients with AML.ResultsUsing 68 known abnormal and 20 karyotypically normal AML samples, each recurrent primary AML‐specific abnormality previously identified in the abnormal samples was confirmed using MPseq. Importantly, in eight cases with abnormalities that could not be resolved by conventional cytogenetic studies, MPseq was utilized to molecularly define eight recurrent AML‐fusion events. In addition, MPseq uncovered two cryptic abnormalities that were missed by conventional cytogenetic studies. Thus, MPseq improved the diagnostic yield in the detection of AML‐specific structural rearrangements in 10/88 (11%) of cases analyzed.ConclusionUtilization of MPseq represents a precise, molecular‐based technique that can be used as an alternative to conventional cytogenetic studies for newly diagnosed AML patients with the potential to revolutionize the diagnosis of hematologic malignancies.

AbstractCopy number variation (CNV) is a common form of structural variation detected in human genomes, occurring as both constitutional and somatic events. Cytogenetic techniques like chromosomal microarray (CMA) are widely used in analyzing CNVs. However, CMA techniques cannot resolve the full nature of these structural variations (i.e. the orientation and location of associated breakpoint junctions) and must be combined with other cytogenetic techniques, such as karyotyping or FISH, to do so. This makes the development of a next‐generation sequencing (NGS) approach capable of resolving both CNVs and breakpoint junctions desirable. Mate‐pair sequencing (MPseq) is a NGS technology designed to find large structural rearrangements across the entire genome. Here we present an algorithm capable of performing copy number analysis from mate‐pair sequencing data. The algorithm uses a step‐wise procedure involving normalization, segmentation, and classification of the sequencing data. The segmentation technique combines both read depth and discordant mate‐pair reads to increase the sensitivity and resolution of CNV calls. The method is particularly suited to MPseq, which is designed to detect breakpoint junctions at high resolution. This allows for the classification step to accurately calculate copy number levels at the relatively low read depth of MPseq. Here we compare results for a series of hematological cancer samples that were tested with CMA and MPseq. We demonstrate comparable sensitivity to the state‐of‐the‐art CMA technology, with the benefit of improved breakpoint resolution. The algorithm provides a powerful analytical tool for the analysis of MPseq results in cancer.

A 5-year-old boy presented with mild autism and attention-deficit hyperactivity disorder (ADHD). Chromosomal microarray demonstrated a 1.7 Mb deletion at Xp22.31, which was consistent with X-linked ichthyosis (XLI). Further exam revealed dry, scaly skin on his abdomen and pretibial areas. Patients with mutations involving solely the STS gene or the recurrent ~2 Mb deletion may present with ADHD, whereas those with larger deletions including the NLGN4 gene can present with both ADHD and autism. However, our patient presented with mild autism in addition to ADHD despite having only the recurrent deletion without loss of NLGN4. Such neurological manifestations of XLI warrant attention as practical targets of clinical management.

Background.Noninvasive prenatal screening (NIPS) is revolutionizing prenatal screening as a result of its increased sensitivity, specificity. NIPS analyzes cell-free fetal DNA (cffDNA) circulating in maternal plasma to detect fetal chromosome abnormalities. However, cffDNA originates from apoptotic placental trophoblast; therefore cffDNA is not always representative of the fetus. Although the published data for NIPS testing states that the current technique ensures high sensitivity and specificity for aneuploidy detection, false positives are possible due to isolated placental mosaicism, vanishing twin or cotwin demise, and maternal chromosome abnormalities or malignancy.Results.We report a case of false negative cell-free DNA (cfDNA) screening due to fetoplacental mosaicism. An infant male with negative cfDNA screening result was born with multiple congenital abnormalities. Postnatal chromosome and FISH studies on a blood specimen revealed trisomy 13 in 20/20 metaphases and 100% interphase nuclei, respectively. FISH analysis on tissues collected after delivery revealed extraembryonic mosaicism.Conclusions.Extraembryonic tissue mosaicism is likely responsible for the false negative cfDNA screening result. This case illustrates that a negative result does not rule out the possibility of a fetus affected with a trisomy, as cffDNA is derived from the placenta and therefore may not accurately represent the fetal genetic information.