Lactate Metabolism in Human Lung Tumors.

Cancer cells consume glucose and secrete lactate in culture. It is unknown whether lactate contributes to energy metabolism in living tumors. We previously reported that human non-small-cell lung cancers (NSCLCs) oxidize glucose in the tricarboxylic acid (TCA) cycle. Here, we show that lactate is also a TCA cycle carbon source for NSCLC. In human NSCLC, evidence of lactate utilization was most apparent in tumors with high 18fluorodeoxyglucose uptake and aggressive oncological behavior. Infusing human NSCLC patients with 13C-lactate revealed extensive labeling of TCA cycle metabolites. In mice, deleting monocarboxylate transporter-1 (MCT1) from tumor cells eliminated lactate-dependent metabolite labeling, confirming tumor-cell-autonomous lactate uptake. Strikingly, directly comparing lactate and glucose metabolism in vivo indicated that lactate's contribution to the TCA cycle predominates. The data indicate that tumors, including bona fide human NSCLC, can use lactate as a fuel in vivo.

Metabolic Heterogeneity in Human Lung Tumors.

Non-small cell lung cancer (NSCLC) is heterogeneous in the genetic and environmental parameters that influence cell metabolism in culture. Here, we assessed the impact of these factors on human NSCLC metabolism in vivo using intraoperative (13)C-glucose infusions in nine NSCLC patients to compare metabolism between tumors and benign lung. While enhanced glycolysis and glucose oxidation were common among these tumors, we observed evidence for oxidation of multiple nutrients in each of them, including lactate as a potential carbon source. Moreover, metabolically heterogeneous regions were identified within and between tumors, and surprisingly, our data suggested potential contributions of non-glucose nutrients in well-perfused tumor areas. Our findings not only demonstrate the heterogeneity in tumor metabolism in vivo but also highlight the strong influence of the microenvironment on this feature.

Comparison of 2 T-Cell Receptor-γ Clonality Assays on Skin Biopsies Suspicious for Mycosis Fungoides.

ABSTRACT: PCR-based fragment analysis of the T-cell receptor (TCR) gene is used extensively in diagnostic labs to assess clonality in T-cell populations in multiple tissue sites. Of the numerous TCR assays that have been reported, studies assessing use on biopsies suspicious for mycosis fungoides specifically are lacking. We compared clonality findings from a previously run 2-tube/2-fluorochrome dye assay to a redesigned 1-tube/1-fluorochrome dye assay on formalin-fixed skin biopsies. Overall, the accuracy of the 2-tube assay was marginally better (75.7% vs. 71.4%), when using clinical history combined with histologic diagnosis as the gold standard. The 2-tube assay had better sensitivity (73.7% vs. 65.8%), while the 1-tube assay had superior specificity (93.8% vs. 87.5%). Clonality results were easier to interpret with the 1-tube assay. In nearly 19% of cases, a change of assays on the same biopsy resulted in a change of clonality interpretation. For laboratories that change TCR-γ clonality assays, follow-up biopsies for mycosis fungoides assessment may result in a change of diagnosis.

Multiplex Fragment Analysis for Flexible Detection of All SARS-CoV-2 Variants of Concern.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to emerge, and effective tracking requires rapid return of results. Surveillance of variants is typically performed by whole genome sequencing (WGS), which can be financially prohibitive and requires specialized equipment and bioinformatic expertise. Genotyping approaches are rapid methods for monitoring SARS-CoV-2 variants but require continuous adaptation. Fragment analysis may represent an approach for improved SARS-CoV-2 variant detection. METHODS: A multiplex fragment analysis approach (CoVarScan) was validated using PCR targeting variants by size and fluorescent color. Eight SARS-CoV-2 mutational hot spots in variants of concern (VOCs) were targeted. Three primer pairs (recurrently deleted region [RDR] 1, RDR2, and RDR3-4) flank RDRs in the S-gene. Three allele-specific primers target recurrent spike receptor binding domain mutants. Lastly, 2 primer pairs target recurrent deletions or insertions in ORF1A and ORF8. Fragments were resolved and analyzed by capillary electrophoresis (ABI 3730XL), and mutational signatures were compared to WGS results. RESULTS: We validated CoVarScan using 3544 clinical respiratory specimens. The assay exhibited 96% sensitivity and 99% specificity compared to WGS. The limit of detection for the core targets (RDR1, RDR2, and ORF1A) was 5 copies/reaction. Variants were identified in 95% of samples with cycle threshold (CT) <30 and 75% of samples with a CT 34 to 35. Assay design was frozen April 2021, but all subsequent VOCs have been detected including Delta (n = 2820), Mu, (n = 6), Lambda (n = 6), and Omicron (n = 309). Genotyping results are available in as little as 4 h. CONCLUSIONS: Multiplex fragment analysis is adaptable and rapid and has similar accuracy to WGS to classify SARS-CoV-2 variants.

BRAF mutation leading to central nervous system rosai-dorfman disease.

Rosai-Dorfman disease (RDD) is an uncommon histiocytic proliferative disorder that can present in nodal, extranodal, or, extremely rarely, in central nervous system (CNS)-restricted form. RDD is characterized histologically as a non-Langerhans cell histiocytosis composed of atypical CD68+ /S-100+ /CD1a- macrophages demonstrating prominent emperipolesis and effacement of the surrounding tissue. Previously thought to represent a reactive process, recent studies have raised the possibility that RDD and other histiocytic lesions, including Erdheim-Chester and Langerhans cell histiocytosis, are clonal processes linked to somatic mutations in the mitogen-activated protein (MAP) kinase pathway. Herein, we present a fatal case of RDD isolated to the CNS and used a next-generation targeted gene panel and Sanger sequencing to uncover a pathogenic deletion in the ß3-αC loop of the kinase domain in exon 12 of BRAF. This mutation, previously described in melanoma and Langerhans cell histiocytosis, represents the first BRAF mutation of this kind identified in RDD. These findings support the idea that RDD is a neoplastic condition and raise the possibility that inhibitors of the MAP kinase pathway may be effective in RDD. Ann Neurol 2018;83:147-152.

Rapid progression to glioblastoma in a subset of IDH-mutated astrocytomas: a genome-wide analysis.

According to the recently updated World Health Organization (WHO) classification (2016), grade II-III astrocytomas are divided into IDH-wildtype and IDH-mutant groups, the latter being significantly less aggressive in terms of both progression-free and total survival. We identified a small cohort of WHO grade II-III astrocytomas that harbored the IDH1 R132H mutation, as confirmed by both immunohistochemistry and molecular sequence analysis, which nonetheless had unexpectedly rapid recurrence and subsequent progression to glioblastoma. Among these four cases, the mean time to recurrence as glioblastoma was only 16 months and the mean total survival among the three patients who have died during the follow-up was only 31 months. We hypothesized that these tumors had other, unfavorable genetic or epigenetic alterations that negated the favorable effect of the IDH mutation. We applied genome-wide profiling with a methylation array (Illumina Infinium Human Methylation 450k) to screen for genetic and epigenetic alterations in these tumors. As expected, the methylation profiles of all four tumors were found to match most closely with IDH-mutant astrocytomas. Compared with a control group of four indolent, age-similar WHO grade II-III astrocytomas, the tumors showed markedly increased levels of overall copy number changes, but no consistent specific genetic alterations were seen across all of the tumors. While most IDH-mutant WHO grade II-III astrocytomas are relatively indolent, a subset may rapidly recur and progress to glioblastoma. The precise underlying cause of the increased aggressiveness in these gliomas remains unknown, although it may be associated with increased genomic instability.

Defining early mycosis fungoides: validation of a diagnostic algorithm proposed by the International Society for Cutaneous Lymphomas.

BACKGROUND: Mycosis fungoides (MF) is the most common subtype of cutaneous T-cell lymphoma and is often difficult to diagnose. Early-stage disease is particularly challenging and requires clinical and histopathologic correlation to make an accurate diagnosis. In order to facilitate the diagnosis of early MF, an algorithm has been proposed by the International Society for Cutaneous Lymphomas (ISCL) whereby clinical and histopathologic characteristics as well as immunohistochemistry and T-cell receptor gene rearrangement studies may be applied to suspected cases of MF. The diagnostic utility of this algorithm has not yet been validated. We sought to determine the validity of the proposed algorithm via an investigator-blinded, retrospective, case-control study. METHODS: A total of 34 cases were randomly selected from the database of a clinic for cutaneous T-cell lymphomas and included patients with MF and patients with clinicopathologic mimics. The proposed diagnostic algorithm was systematically applied to the entire cohort. Each case was assigned a composite score based on the parameters in the proposed algorithm. RESULTS: Among the 24 cases of MF, 21 cases achieved four or more points through application of the algorithm. Among the 10 cases of MF mimics, only four achieved four or more points. This difference was significant (Fisher's exact test, p = 0.009). The sensitivity of the 4-point threshold for a diagnosis of MF was 87.5% and the specificity was 60%. CONCLUSIONS: The diagnostic algorithm proposed by the ISCL is a statistically valid method for defining cases of early MF and distinguishing these cases from other benign dermatoses. However, the clinical utility of the algorithm may be limited by its low specificity. Further refinement of the algorithm may improve its accuracy.

High expression of the stem cell marker nestin is an adverse prognostic factor in WHO grade II-III astrocytomas and oligoastrocytomas.

Infiltrating astrocytomas and oligoastrocytomas of low to anaplastic grade (WHO grades II and III), in spite of being associated with a wide range of clinical outcomes, can be difficult to subclassify and grade by the current histopathologic criteria. Unlike oligodendrogliomas and anaplastic oligodendrogliomas that can be identified by the 1p/19q codeletion and the more malignant glioblastomas (WHO grade IV astrocytomas) that can be diagnosed solely based on objective features on routine hematoxylin and eosin sections, no such objective criteria exist for the subclassification of grade II-III astrocytomas and oligoastrocytomas (A+OA II-III). In this study, we evaluated the prognostic and predictive value of the stem cell marker nestin in adult A+OA II-III (n = 50) using immunohistochemistry and computer-assisted analysis on tissue microarrays. In addition, the correlation between nestin mRNA level and total survival was analyzed in the NCI Rembrandt database. The results showed that high nestin expression is a strong adverse prognostic factor for total survival (p = 0.0004). The strength of the correlation was comparable to but independent of the isocitrate dehydrogenase 1/2 (IDH 1/2) mutation status. Histopathological grading and subclassification did not correlate significantly with outcome, although the interpretation of this finding is limited by the fact that grade III tumors were treated more aggressively than grade II tumors. These results suggest that nestin level and IDH 1/2 mutation status are strong prognostic features in A+OA II-III and possibly more helpful for treatment planning than routine histopathological variables such as oligodendroglial component (astrocytoma vs. oligoastrocytoma) and WHO grade (grade II vs. III).

Serum D-2-hydroxyglutarate and the ratio of D-2HG/L-2HG predict IDH mutation in acute myeloid leukemia.

This study investigates whether serum D-2HG (D-2-hydroxyglutarate) produced by the mutated isocitrate dehydrogenase (IDH) can predict IDH mutations in acute myeloid leukemia (AML) at diagnosis. D-2HG and L-2HG are measured by liquid chromatography-tandem mass spectrometry. D-2HG, total 2HG and the D/L ratio (D-2HG/L-2HG) are significantly higher in IDH mutated cases than in IDH wild cases. The optimal cutoff values to predict IDH mutations at 100% sensitivity (specificity 91%-94%) are >588 ng/mL for D-2HG and >2.33 for the D/L ratio. Our study indicates that elevated serum D-2HG and the D/L ratio may serve as noninvasive biomarkers of IDH mutation in AML.

Stepped Behavioral and Biological Screening for Oral Oncogenic HPV DNA in Middle-aged and Elderly Adults: A Feasibility Study.

Novel preventive interventions are needed to address the rising incidence of human papillomavirus (HPV)-mediated oropharyngeal cancer (HPV+ OPC). This pilot study evaluated the feasibility of a stepped, behavioral and biological screening program for oral oncogenic HPV infection, an intermediate HPV+ OPC outcome.This was a cross-sectional, feasibility study. Eligible 45-74 years old adults identified from three clinical research registries were administered a behavioral risk survey (step 1). Participant tobacco use and sexual behavior history were translated into a quantifiable risk of oral oncogenic HPV DNA, according to prior National Health and Nutrition Examination Survey analyses. Females with >2% risk and males with >7% risk were offered biological screening for oral oncogenic HPV DNA (step 2) via an oral rinse and gargle specimen.A total of 292 individuals were contacted, but only 144 (49%) were reached. Among these, 56 individuals (19%) were uninterested and 18 (13%) were ineligible. Seventy individuals began the survey and 66 completed it (step 1), among whom 46 were classified as low-risk. Among the remaining 20 participants classified as high-risk for an oral oncogenic HPV infection, 5% were current smokers and the median participant had performed oral sex on 10 unique partners. During step 2 (biological screening), 45% (9/20) completed testing, all of whom tested negative for oral oncogenic HPV DNA.In this pilot of a stepped, oral oncogenic HPV screening program, enrollment and study completion were suboptimal. These barriers to screening should be characterized and addressed before reevaluating the feasibility of this program. PREVENTION RELEVANCE: Novel preventive interventions are needed to address the rising incidence of HPV+ OPC. In this feasibility study, we characterized barriers to a two-step, behavioral and biological screening program for oral oncogenic HPV infection, an intermediate outcome for HPV+ OPC.

Distinct immunophenotype of early T-cell progenitors in T lymphoblastic leukemia/lymphoma may predict FMS-like tyrosine kinase 3 mutations.

FMS-like tyrosine kinase 3 (FLT3) mutation in T lymphoblastic leukemia/lymphoma (T-LL) is rare (∼4%) and reported only in cases with CD117 expression. This study aimed to identify the immunophenotypic features that may predict FLT3 mutations. We report 3 (43%) of 7 CD117(+) T-LL cases harboring FLT3-internal tandem duplication mutation. Compared with 4 FLT3-unmutated cases, all 3 FLT3-mutated cases had a distinct immunophenotype (CD1a(-)/CD2(+)/CD7(+)/CD34(+)/CD117(uniform+)/Tdt(+)) corresponding to the stage of earliest thymic T-cell progenitors possessing myeloid lineage potential. Indeed, all FLT3-mutated T-LL cases expressed myeloperoxidase on a very small subset of blasts and, thus, may be further considered a mixed phenotype acute leukemia, T/myeloid, by the 2008 World Health Organization classification scheme. We conclude that this unique immunophenotype (CD1a(-)/CD2(+)/CD7(+)/CD34(+)/CD117(+)/Tdt(+)) is a better predictor of FLT3 mutation than sole CD117 expression.

Case Report of Fibro-Adipose Vascular Anomaly (FAVA) with Activating Somatic PIK3CA Mutation.

Fibro-adipose vascular anomaly (FAVA) is a recently described complex and painful benign lesion found in young adults and the pediatric population composed of intramuscular vascular, fibrous, and adipose tissues. A previous report has identified the presence of somatic mosaic mutations in the gene for the catalytic subunit of phosphatidylinositol 3-kinase (PIK3CA) in cases of FAVA. Herein, we present a case of FAVA found in a 23-year-old male patient who presented with chronic wrist pain associated with a mass, and we identified an associated somatic activating mutation (H1047R) in PIK3CA. We briefly review the relevant literature surrounding the identification and histology of FAVA, the known mutational spectrum, downstream signaling pathways, and relevant treatment modalities. Our case highlights the association between FAVA and somatic mosaic activating PIK3CA mutations.

Digital Droplet PCR for SARS-CoV-2 Resolves Borderline Cases.

OBJECTIVES: The Bio-Rad SARS-CoV-2 ddPCR Kit (Bio-Rad Laboratories) was the first droplet digital polymerase chain reaction (ddPCR) assay to receive Food and Drug Administration (FDA) Emergency Use Authorization approval, but it has not been evaluated clinically. We describe the performance of ddPCR-in particular, its ability to confirm weak-positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) results. METHODS: We clinically validated the Bio-Rad Triplex Probe ddPCR Assay. The limit of detection was determined by using serial dilutions of SARS-CoV-2 RNA in an artificial viral envelope. The ddPCR assay was performed according to the manufacturer's specifications on specimens confirmed to be positive (n = 48) or negative (n = 30) by an FDA-validated reverse transcription-polymerase chain reaction assay on the m2000 RealTime system (Abbott). Ten borderline positive cases were also evaluated. RESULTS: The limit of detection was 50 copies/mL (19 of 20 positive). Forty-seven specimens spanning a range of quantification cycles (2.9-25.9 cycle numbers) were positive by this assay (47 of 48; 97.9% positive precent agreement), and 30 negative samples were confirmed as negative (30 of 30; 100% negative percent agreement). Nine of 10 borderline cases were positive when tested in triplicate. CONCLUSIONS: The ddPCR of SARS-CoV-2 is an accurate method, with superior sensitivity for viral RNA detection. It could provide definitive evaluation of borderline positive cases or suspected false-negative cases.

Transcriptionally Active HPV and Targetable EGFR Mutations in Sinonasal Inverted Papilloma: An Association Between Low-risk HPV, Condylomatous Morphology, and Cancer Risk?

Sinonasal inverted papillomas (IPs) commonly recur, and transform to malignancy in 5% to 10% of patients. It has long been debated whether IPs are caused by high-risk or low-risk (lr) human papillomavirus (HPV) and whether the HPV is transcriptionally active. EGFR mutations have also been recently implicated in the pathogenesis of IP with an unclear relationship to HPV status. IP cases over a 10-year period were tested for p16 by immunohistochemistry and for transcriptionally active hrHPV and lrHPV by reverse-transcriptase real-time polymerase chain reaction and RNA in situ hybridization, respectively. EGFR tyrosine kinase domain Sanger sequencing was performed on all lrHPV RNA positive and 15 randomly selected lrHPV RNA negative IPs. Seven sinonasal nonkeratinizing squamous cell carcinomas (SCCs) without associated IP were included as controls. Of the 44 IPs, 5 (11.4%) were associated with SCC, all keratinizing type. All IPs and associated SCCs were negative for p16 and hrHPV. lrHPV RNA was detected in 5/42 (12%) cases, including 3/5 (60%) with associated SCC (P=0.009). All 5 lrHPV RNA positive IPs involved the nasal cavity, had a distinct, condylomatous morphology, and were EGFR wild-type. In contrast, 11/15 (73.3%) lrHPV RNA negative IPs that were sequenced had EGFR exon 19 or 20 mutations. All control nonkeratinizing SCCs were lrHPV RNA negative, but 5/7 (71.4%) were p16 and high-risk HPV RNA positive. This study shows that a subset of IPs involving the nasal cavity have transcriptionally active lrHPV, condylomatous morphology, and possibly increased risk of malignancy. Furthermore, lrHPV positivity is mutually exclusive with EGFR mutations, which suggests alternate mechanisms of pathogenesis.

Lenalidomide-Associated Secondary B-Lymphoblastic Leukemia/Lymphoma-A Unique Entity.

OBJECTIVES: Autologous stem cell transplant with lenalidomide maintenance therapy has greatly improved the relapse-free and overall survival rates of patients with multiple myeloma but also has been associated with an increased risk of secondary B-lymphoblastic leukemia/lymphoma (B-ALL). METHODS: We report a comprehensive review of the clinicopathologic features of 2 patients with multiple myeloma who developed secondary B-ALL during lenalidomide maintenance. RESULTS: Our observations showed that the disease may initially present with subtle clinical, morphologic, and flow-cytometric findings. The flow cytometry findings in such cases may initially mimic an expansion of hematogones with minimal immunophenotypic variation. Both patients achieved complete remission of secondary B-ALL after standard chemotherapy; however, one patient continues to have minimal residual disease, and the other experienced relapse. Next-generation sequencing of the relapse specimen showed numerous, complex abnormalities, suggesting clonal evolution. CONCLUSIONS: Our findings suggest the need for increased awareness and further study of this unique form of secondary B-ALL.

Does Tumor FDG-PET Avidity Represent Enhanced Glycolytic Metabolism in Non-Small Cell Lung Cancer?

BACKGROUND: In non-small cell lung cancer (NSCLC), 18fluoro-2-deoxyglucose-positron emission tomography (FDG-PET) assists in diagnosis, staging, and evaluating treatment response. One variable of FDG-PET, the maximum standard uptake value (SUVm), is considered an objective measure of glucose uptake. However, little is known about the fate of glucose in FDG-avid lung tumors in vivo. This study used stable glucose isotope tracing to determine whether the SUVm predicts glycolytic metabolism or other glucose fates in tumors. METHODS: In this prospective Institutional Review Board-approved clinical trial, 52 untreated potentially resectable confirmed NSCLC patients underwent FDG-PET computed tomography. During the surgical procedure, the patients were infused with 13C-labeled glucose. Blood, tumor, and normal lung samples were analyzed by mass spectrometry to determine 13C enrichment in glycolytic intermediates. These values were compared with clinical variables, including SUVm, maximum tumor diameter, stage, grade, and MIB-1/Ki67 proliferation index. RESULTS: For each patient, 13C enrichment in each metabolite was compared between tumor and adjacent lung. Although all tumors metabolized glucose, SUVm did not correlate with glycolytic intermediate labeling. Rather, SUVm correlated with markers indicating the use of other respiratory substrates, including lactate, and with the proliferation index. CONCLUSIONS: SUVm does not correlate with glycolytic metabolism in human NSCLC but does correlate with the proliferation index, suggesting that SUVm predicts glucose use by pathways other than glycolysis. These pathways may offer alternative therapeutic targets, including biosynthetic pathways required for cell proliferation. The research techniques in this study offer the opportunity to understand the relationships between SUVm, tumor metabolism, and therapeutic vulnerabilities in human NSCLCs.

Intestinal edema: effect of enteral feeding on motility and gene expression.

OBJECTIVE: Edema formation, inflammation, and ileus in the intestine are commonly seen in conditions like gastroschisis, inflammatory bowel disease, and cirrhosis. We hypothesized that early enteral feeding would improve intestinal transit. We also wanted to study the impact of early enteral feeding on global gene expression in the intestine. DESIGN: Rats were divided into Sham or Edema +/- immediate enteral nutrition (IEN). At 12 h, small intestinal transit via FITC-Dextran and tissue water were measured. Ileum was harvested for total RNA to analyze gene expression using cDNA microarray with validation using real-time PCR. Data are expressed as mean +/- SEM, n = 4-6 and (*), (**) = P < 0.05 versus all groups using ANOVA. RESULTS: IEN markedly improved intestinal transit with minimal genetic alterations in Edema animals. Major alterations in gene expression were detected in primary, cellular and macromolecular metabolic activities. Edema also altered more genes involved with the regulation of the actin cytoskeleton. CONCLUSIONS: Intestinal edema results in impaired small intestinal transit and globally increased gene expression. Early enteral nutrition improves edema-induced impaired transit and minimizes gene transcriptional activity.

Cytogenomic characterization of double minute heterogeneity in therapy related acute myeloid leukemia.

Breast cancer patients treated with adjuvant chemotherapy regimens containing alkylating agents and anthracyclines are at an increased risk for secondary myeloid malignancies, either acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Complex genomic changes (karyotypes and/or gene amplification) accompany the development of the secondary neoplasms. Here we present a unique case of a breast cancer patient who developed secondary AML within 18 months of treatment with trastuzumab, pertuzumab, docetaxel, carboplatin (TCHP) and radiation. Leukemia cells had catastrophic alterations in chromosomes 8, 11, and 17. Genetic abnormalities in the leukemia cells included amplification of MYC and KMT2A as double minutes, and deletion and mutational inactivation of TP53 Concurrent amplification of different genes at different levels and on different double minutes, we have named "double minute heterogeneity." Clinically, this case highlights the need to identify genes amplified in secondary myeloid malignancies by cytogenomic microarray (CMA) analysis since these may have therapeutic implications.

Spinal Pleomorphic Xanthoastrocytoma With a QKI-RAF1 Fusion.

Pleomorphic xanthoastrocytoma (PXA) is a slow-growing neoplasm that predominantly affects the pediatric and young adult population. This neoplasm has a good prognosis, with a median 10-year survival rate of 70%. The majority of tumors are supratentorial and arise in the temporal lobe, while spinal tumors are extremely rare, with only 8 reported cases. Molecular perturbations involving the MAPK/ERK signaling pathway have been described in PXAs. The most common mutation is BRAF V600E in 60%-80% of cases. Other mechanisms activating this pathway in the absence of this mutation are rare and include CRAF (RAF1) fusion genes. We report a PXA case in the cervical spinal cord of a 49-year-old man with slowly progressive coordination difficulties and extremity numbness. The tumor was negative for the V600E mutation, but 2 RNA sequencing platforms detected a QKI-RAF1 fusion (t(6; 3)(q26; p25)), which has not been previously reported in PXAs. This fusion is known to activate MAPK/ERK and PI3K/mTOR signaling. Although first- and second-generation RAF inhibitors are predicted to be ineffective, this fusion may be targetable by the novel RAF inhibitor LY3009120 and to some extent by the MEK inhibitor trametinib. Genetic analysis to screen for MAPK/ERK pathway mutations is warranted on PXAs negative for the V600E mutation.