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High-grade histologic transformation of low-grade endometrial stromal sarcoma (LGESS) is rare. Here, we describe the clinicopathologic features and gene fusion status of 12 cases (11 primary uterine corpus and 1 primary vaginal), 11 diagnosed prospectively from 2016, and 1 retrospectively collected. Targeted RNA sequencing and/or fluorescence in situ hybridization was employed in all cases. High-grade transformation was seen at the time of initial diagnosis in eight patients and at the time of recurrence in four patients, 4–11 years after initial diagnosis of LGESS. High-grade morphology consisted of generally uniform population of round to epithelioid cells with enlarged nuclei one to two times larger than a lymphocyte, visible nucleoli, and increased mitotic index (range, 6–30; median, 16 per 10 high-power fields); there was often an associated sclerotic and/or myxoid stroma. Estrogen receptor, progesterone receptor, and CD10 expression was absent or significantly decreased (compared with the low-grade component) in the high-grade foci of five tumors. One tumor demonstrated positive (diffuse and strong) cyclin D1 and BCOR staining. p53 staining was wild type in both components of all eight tumors tested. JAZF1-SUZ12(n= 6), JAZF1-PHF1(n= 3), EPC1-PHF1, (n= 1), or BRD8-PHF1(n= 1) fusions were detected in 11 tumors; no fusions were found in one by targeted RNA sequencing. Patients presented with FIGO stages I (n= 4), II (n= 4), III (n= 1), and IV disease (n= 2). Median overall survival calculated from the time of histologic transformation was 22 months (range, 8 months to 8 years) with five patients who died of disease 8–18 months after transformation. High-grade transformation may occur in LGESS with JAZF1and PHF1rearrangements at the time of or years after initial diagnosis. Such high-grade transformation is characterized by nuclear enlargement, prominent nucleoli, and increased mitotic index compared with typical LGESS. Histologic high-grade transformation may herald aggressive behavior.

Herein we described the clinical, radiological, histological, and molecular characteristics of seven soft tissue aneurysmal bone cysts (STABCs) diagnosed and managed at a tertiary cancer center and to elucidate their relationship with myositis ossificans (MO). All cases had established imaging and histopathological diagnosis of STABC and were subject to fluorescence in situ hybridization (FISH) for USP6rearrangement and Archer® FusionPlex® targeted RNA sequencing (RNASeq) analysis to identify the fusion partner. A thorough literature review of STABC and MO was conducted. The patients presented with painful masses unpreceded by trauma, occurring most commonly in the deep soft tissue of the thigh/gluteus (4/7), and also in the supraclavicular region, the axilla, and the hand. On imaging, the lesions were frequently associated with peripheral calcification on conventional radiographs and CT (6/7), cystic components on ultrasound, as well as perilesional edema (7/7) and fluid levels (3/7) on MRI. Bone scan (1/1) showed intense radiotracer uptake. Histologically, 6/7 cases demonstrated zonal arrangements reminiscent of MO. USP6rearrangement was found in all seven cases by FISH and/or RNASeq. RNASeq further detected COL1A1-USP6fusion in six cases and a novel ANGPTL2-USP6fusion in one case. Four patients underwent resection of the tumors and were disease free at their last follow-up. Three patients who underwent incisional or needle biopsies had no evidence of disease progression on imaging studies. In conclusion, the clinical, radiological, and pathological overlap between STABC and MO suggests that they are closely related entities. A novel fusion ANGPTL2-USP6is associated with distinct clinical and pathological presentation.

Adenosarcoma can mimic high-grade endometrial stromal sarcoma with ZC3H7B-BCORfusion that may show entrapped glands and often exhibits diffuse BCOR expression. We encountered diffuse BCOR expression in rare adenosarcomas and sought to define its frequency among a larger cohort of these tumors. BCOR immunohistochemistry was performed on archival formalin-fixed paraffin-embedded tumor tissue in 13 of 14 adenosarcomas with and without stromal overgrowth arising in the uterus or ovary. The staining intensity and percentage of positive tumor nuclei in the mesenchymal component were evaluated. Eleven cases with sufficient tumoral tissue were subjected to fluorescence in situ hybridization for the detection of BCOR, BCORL1, NUTM1, ZC3H7B, and JAZF1rearrangement. Three cases were subjected to targeted RNA sequencing. BCOR was expressed in 9 of 13 (70%) tumors, including 6 with and 3 without stromal overgrowth. Moderate to strong staining in >70% of cells was seen throughout in 1 low-grade and 6 high-grade tumors, 5 of which had stromal overgrowth. No staining was seen in 3 low-grade and 1 high-grade tumors with stromal overgrowth. One tumor demonstrating extensive sex cord-like differentiation and diffuse BCOR expression harbored JAZF1and BCORL1rearrangements. No BCORor BCORL1rearrangement was identified in the remaining tumors. BCOR expression is seen in most adenosarcomas with and without stromal overgrowth. BCORL1rearrangement is seen in rare tumors with diffuse BCOR expression. Assessment of BCORor BCORL1rearrangement status is required in adenosarcomas demonstrating BCOR expression.

Immunohistochemistry for mismatch repair protein expression is widely used as a surrogate for microsatellite instability status—an important signature for immunotherapy and germline testing. There are no systematic analyses examining the sensitivity of immunohistochemistry for microsatellite instability-high status. Mismatch repair immunohistochemistry and microsatellite instability testing were performed routinely as clinically validated assays. We classified germline/somatic mutation types as truncating (nonsense, frameshift, and in/del) versus missense and predicted pathogenicity of the latter. Discordant cases were compared with concordant groups: microsatellite instability-high/mismatch repair-deficient for mutation comparison and microsatellite stable/mismatch repair-proficient for immunohistochemical comparison. 32 of 443 (7%) microsatellite instability-high cases had immunohistochemistry. Four additional microsatellite instability-high research cases had discordant immunohistochemistry. Of 36 microsatellite instability-high cases with discordant immunohistochemistry, 30 were mismatch repair-proficient, while six (five MLH1 and one MSH2) retained expression of the defective mismatch repair protein and lost its partner. In microsatellite instability-high tumors with discordant immunohistochemistry, we observed an enrichment in deleterious missense mutations over truncating mutations, with 69% (25/36) of cases having pathogenic germline or somatic missense mutations, as opposed to only 19% (7/36) in a matched microsatellite instability-high group with concordant immunohistochemistry (p= 0.0007).  In microsatellite instability-high cases with discordant immunohistochemistry and MLH1or PMS2abnormalities, less cells showed expression (p= 0.015 and p= 0.00095, respectively) compared with microsatellite stable/mismatch repair-proficient cases. Tumor mutation burden, MSIsensor score, and truncating mismatch repair gene mutations were similar between microsatellite instability-high cases with concordant versus discordant immunohistochemical expression. Approximately 6% of microsatellite instability-high cases have retained mismatch repair protein expression and would be missed by immunohistochemistry-based testing, hindering patient access to immunotherapy. Another 1% of microsatellite instability-high cases show isolated loss of the defective gene’s dimerization partner, which may lead to germline testing of the wrong gene. These cases are enriched for pathogenic mismatch repair missense mutations.

Recently discovered DNAJB1-PRKACAoncogenic fusions have been considered diagnostic for fibrolamellar hepatocellular carcinoma. In this study, we describe six pancreatobiliary neoplasms with PRKACAfusions, five of which harbor the DNAJB1-PRKACAfusion. All neoplasms were subjected to a hybridization capture-based next-generation sequencing assay (MSK-IMPACT), which enables the identification of sequence mutations, copy number alterations, and selected structural rearrangements involving ≥410 genes (n= 6) and/or to a custom targeted, RNA-based panel (MSK-Fusion) that utilizes Archer Anchored Multiplex PCR technology and next-generation sequencing to detect gene fusions in 62 genes (n= 2). Selected neoplasms also underwent FISH analysis, albumin mRNA in-situ hybridization, and arginase-1 immunohistochemical labeling (n= 3). Five neoplasms were pancreatic, and one arose in the intrahepatic bile ducts. All revealed at least focal oncocytic morphology: three cases were diagnosed as intraductal oncocytic papillary neoplasms, and three as intraductal papillary mucinous neoplasms with mixed oncocytic and pancreatobiliary or gastric features. Four cases had an invasive carcinoma component composed of oncocytic cells. Five cases revealed DNAJB1-PRKACAfusions and one revealed an ATP1B1-PRKACAfusion. None of the cases tested were positive for albumin or arginase-1. Our data prove that DNAJB1-PRKACAfusion is neither exclusive nor diagnostic for fibrolamellar hepatocellular carcinoma, and caution should be exercised in diagnosing liver tumors with DNAJB1-PRKACAfusions as fibrolamellar hepatocellular carcinoma, particularly if a pancreatic lesion is present. Moreover, considering DNAJB1-PRKACAfusions lead to upregulated protein kinase activity and that this upregulated protein kinase activity has a significant role in tumorigenesis of fibrolamellar hepatocellular carcinoma, protein kinase inhibition could have therapeutic potential in the treatment of these pancreatobiliary neoplasms as well, once a suitable drug is developed.

With the FDA approval of larotrectinib, NTRKfusion assessment has recently become a standard part of management for patients with locally advanced or metastatic cancers. Unlike somatic mutation assessment, the detection of NTRKfusions is not straightforward, and various assays exist at the DNA, RNA, and protein level. Here, we investigate the performance of immunohistochemistry and DNA-based next-generation sequencing to indirectly or directly detect NTRKfusions relative to an RNA-based next-generation sequencing approach in the largest cohort of NTRKfusion positive solid tumors to date. A retrospective analysis of 38,095 samples from 33,997 patients sequenced by a targeted DNA-based next-generation sequencing panel (MSK-IMPACT), 2189 of which were also examined by an RNA-based sequencing assay (MSK-Fusion), identified 87 patients with oncogenic NTRK1-3fusions. All available institutional NTRKfusion positive cases were assessed by pan-Trk immunohistochemistry along with a cohort of control cases negative for NTRKfusions by next-generation sequencing. DNA-based sequencing showed an overall sensitivity and specificity of 81.1% and 99.9%, respectively, for the detection of NTRKfusions when compared to RNA-based sequencing. False negatives occurred when fusions involved breakpoints not covered by the assay. Immunohistochemistry showed overall sensitivity of 87.9% and specificity of 81.1%, with high sensitivity for NTRK1(96%) and NTRK2(100%) fusions and lower sensitivity for NTRK3fusions (79%). Specificity was 100% for carcinomas of the colon, lung, thyroid, pancreas, and biliary tract. Decreased specificity was seen in breast and salivary gland carcinomas (82% and 52%, respectively), and positive staining was often seen in tumors with neural differentiation. Both sensitivity and specificity were poor in sarcomas. Selection of the appropriate assay for NTRKfusion detection therefore depends on tumor type and genes involved, as well as consideration of other factors such as available material, accessibility of various clinical assays, and whether comprehensive genomic testing is needed concurrently.

Multiple genetic mechanisms have been identified in EGFR-mutant lung cancers as mediators of acquired resistance (AR) to EGFR tyrosine kinase inhibitors (TKIs), but many cases still lack a known mechanism.

Half of inflammatory myofibroblastic tumors (IMTs) regardless of anatomic location harbor anaplastic lymphoma kinase gene (ALK) rearrangements and overexpress anaplastic lymphoma kinase protein. The wide application of next-generation sequencing and the clinical benefit to tyrosine kinase inhibitors have opened new opportunities for investigation of ALK-negative IMTs.

Integration of morphological, immunohistochemical, and molecular methods is often necessary for the precise diagnosis and optimal clinical management of sarcomas. We have validated and implemented a clinical molecular diagnostic assay, MSK- Fusion Solid, for detection of gene fusions in solid tumors, including sarcomas. Starting with RNA extracted from formalin-fixed paraffin-embedded tumor material, this targeted RNA sequencing assay utilizes anchored multiplex PCR to detect oncogenic fusion transcripts involving 62 genes known to be recurrently rearranged in solid tumors including sarcomas without prior knowledge of fusion partners. From 1/2016 to 1/2018, 192 bone and soft tissue tumors were submitted for MSK- Fusion Solid analysis and 96% (184/192) successfully passed all the pre-sequencing quality control parameters and sequencing steps. These sarcomas encompass 24 major tumor types, including 175 soft tissue tumors and 9 osteosarcomas. Ewing and Ewing-like sarcomas, rhabdomyosarcoma, and sarcoma-not otherwise specified were the three most common tumor types. Diagnostic in-frame fusion transcripts were detected in 43% of cases, including 3% (6/184) with novel fusion partners, specifically TRPS1-PLAG1, VCP-TFE3, MYLK-BRAF, FUS-TFCP2, and ACTB-FOSB, the latter in two cases of pseudomyogenic hemangioendothelioma, representing a novel observation in this sarcoma. Our experience shows that this targeted RNA sequencing assay performs in a robust and sensitive fashion on RNA extracted from most routine clinical specimens of sarcomas thereby facilitating precise diagnosis and providing opportunities for novel fusion partner discovery.

Genetic alterations in uterine myxoid leiomyosarcoma are unknown. We investigate the clinicopathologic features of 19 uterine tumors previously diagnosed as myxoid leiomyosarcomas in which tumoral RNA was subjected to targeted RNA sequencing. PLAG1, BCOR, BCORL1, HMGA2, and ALKbreak-apart fluorescence in situ hybridization (FISH) and BCOR, PLAG1, and ALK immunohistochemistry were performed in cases which failed or lacked fusions by sequencing. The diagnosis of myxoid leiomyosarcoma was confirmed in 15 cases after exclusion of 4 tumors with BCORand ALKrearrangements. These 15 patients presented at a median age of 50 years with stage I (3), II (2), III (2), and IV (1) tumors, respectively; stage was unknown in 7 cases. Tumor size ranged from 10 to 24 cm. Matrix was myxoid in all tumors and also eosinophilic in 2. Cells were spindled, epithelioid, and both in 10, 2, and 3 tumors and showed mild, moderate, and severe nuclear atypia in 3, 8, and 4 tumors, respectively. Mitotic index ranged from <1 to 14/10 HPF, while tumor necrosis was present in 6 (40%). Novel TRPS1-PLAG1or RAD51B-PLAG1fusions were detected by sequencing in 4 tumors, 3 of which were also confirmed by FISH. Diffuse PLAG1 expression was seen in 7 tumors, including 4 with PLAG1rearrangement. No morphologic differences were seen among PLAG1fusion-positive and fusion-negative tumors. No PLAG1, HMGA2, ALK, BCOR, or BCORL1rearrangements were detected by FISH in 11 tumors. On the basis of sequencing and FISH results, PLAG1rearrangements resulting in PLAG1 expression underpin ~25% of myxoid leiomyosarcomas and may serve as a useful diagnostic biomarker. Immunohistochemistry, targeted RNA sequencing, and/or FISH may distinguish myxoid leiomyosarcoma from its morphologic mimics.

Genomic amplification at 9p24.1, including the loci for JAK2, PD-L1, and PD-L2, has recently been described as a mechanism of resistance in postchemotherapy, triple-negative breast cancer. This genomic signature holds significant promise as a prognostic biomarker and has implications for targeted therapy with JAK2 inhibitors, as well as with immunotherapy. To guide future screening strategies, the frequency of these alterations was determined. A total of 5399 cases were included in the study. This encompassed 2890 institutional cases tested by the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets assay and 2509 cases from The Cancer Genome Atlas (TCGA). The combined incidence of 9p24.1 amplifications in both the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets and TCGA cohorts was 1.0% (56/5399 cases) and showed a >10-fold higher incidence in triple-negative breast cancer (triple-negative: 5.1%; non–triple-negative: 0.5%). Tumor mutation burden and stromal tumor infiltrating lymphocytes, parameters used to assess response to immunotherapy, were not significantly higher for these cases. The significance of genomic losses at 9p24.1 is unclear, and further studies are needed. Herein, we studied the spectrum of copy number alterations in breast cancer cases within our institutional clinical sequencing cohort and those profiled by TCGA to determine the frequency of genomic alterations that may predict response or resistance to JAK2 inhibitors and/or immunotherapy.

Supplemental Digital Content is available in the text.Tropomyosin receptor kinase (Trk) inhibitors have shown high response rates in patients with tumors harboring NTRKfusions. We identified 4 NTRKfusion-positive uterine sarcomas that should be distinguished from leiomyosarcoma and undifferentiated uterine sarcoma. NTRKrearrangements were detected by fluorescence in situ hybridization (FISH) and/or targeted RNA or DNA sequencing in 4 undifferentiated uterine sarcomas with spindle cell morphology. Because of histologic overlap with leiomyosarcoma, TrkA and pan-Trk immunohistochemistry was performed in 97 uterine leiomyosarcomas. NTRK1and NTRK3FISH was performed on tumors with TrkA or pan-Trk staining. We also performed whole transcriptome RNA sequencing of a leiomyosarcoma with TrkA expression and targeted RNA sequencing of 2 additional undifferentiated uterine sarcomas. FISH and/or targeted RNA or DNA sequencing in the study group showed TPM3-NTRK1, LMNA-NTRK1, RBPMS-NTRK3, and TPR-NTRK1fusions. All tumors were composed of fascicles of spindle cells. Mitotic index was 7 to 30 mitotic figures per 10 high power fields; tumor necrosis was seen in 2 tumors. Desmin, estrogen receptor, and progesterone receptor were negative in all tumors, while pan-Trk was expressed in all tumors with concurrent TrkA staining in 3 of them. TrkA and/or pan-Trk staining was also seen in 6 leiomyosarcomas, but these tumors lacked NTRKfusions or alternative isoforms by FISH or whole transcriptome sequencing. No fusions were detected in 2 undifferentiated uterine sarcomas. NTRKfusion-positive uterine spindle cell sarcomas constitute a novel tumor type with features of fibrosarcoma; patients with these tumors may benefit from Trk inhibition. TrkA and pan-Trk expression in leiomyosarcomas is rare and does not correlate with NTRKrearrangement.

High-grade endometrial stromal sarcoma likely encompasses underrecognized tumors harboring genetic abnormalities besides YWHAE–NUTM2fusion. Triggered by three initial endometrial stromal sarcomas with ZC3H7B–BCORfusion characterized by high-grade morphology and aggressive clinical behavior, we herein investigate the clinicopathologic features of this genetic subset by expanding the analysis to 17 such tumors. All of them occurred in adult women with a median age of 54 (range, 28–71) years. They were predominantly based in the endomyometrium and demonstrated tongue-like and/or pushing myometrial invasion. Most were uniformly cellular and displayed haphazard fascicles of spindle cells with mild to moderate nuclear atypia. Myxoid matrix was seen in 14 of 17 (82%) tumors, and collagen plaques were seen in 8 (47%). The mitotic index was ≥10 mitotic figures/10 high-power fields (HPFs) in 14 of 17 (82%) tumors with a median of 14.5 mitotic figures/10 HPFs. No foci of conventional or variant low-grade endometrial stromal sarcoma were seen. All tumors expressed CD10 with only limited or absent desmin, SMA and/or h-caldesmon staining. ER and PR expression in >5% of cells was seen in 4 of 12 (33%) tumors. Diffuse cyclin D1 and BCOR immunoreactivity was present in 7 of 8 (88%) and 7 of 14 (50%) tumors, respectively. Fluorescence in situhybridization or targeted RNA sequencing confirmed ZC3H7B–BCORfusion in all tumors, including four and two previously diagnosed as myxoid leiomyosarcoma and undifferentiated uterine sarcoma, respectively. Limited clinical data suggest that patients present at higher stage and have worse prognosis compared with published outcomes in low-grade endometrial stromal sarcoma. Tumors with ZC3H7B–BCORfusion constitute a distinct group of endometrial stromal sarcomas with high-grade morphology that should be distinguished from other uterine mesenchymal neoplasms that may demonstrate myxoid morphology.

Approximately 1–2% of pancreatic neoplasms are acinar cell carcinomas. Recently, BRAFgene rearrangements were identified in over 20% of acinar-type neoplasms, which included both pure acinar cell carcinomas and mixed carcinomas with acinar differentiation, using next-generation sequencing-based platforms, providing a potential therapeutic target for patients with these neoplasms. Thus, it is clinically important to develop a rapid, cost- and material-efficient assay to screen for BRAFgene fusions in pancreatic acinar-type neoplasms. We developed a dual color, break-apart FISH assay to detect BRAFgene rearrangements in these neoplasms and evaluated its performance in comparison to next-generation sequencing-based studies. A blinded BRAFrearrangement FISH investigation was performed on 31 acinar-type neoplasms that had been studied previously by next-generation sequencing-based analysis as well as on 18 additional acinar-type neoplasms that were accrued over the past 2 years. In total, BRAFfusions were identified in 12/49 (24%) acinar-type neoplasms by FISH. BRAFfusion partners were uncovered by using targeted next-generation sequencing studies in 11 FISH-positive cases that had sufficient material for next-generation sequencing studies. SND1was the most frequent fusion partner involved in BRAF-fusion acinar-type neoplasms (50%), followed by HERPUD1(18%). No BRAFfusions were identified by next-generation sequencing in any of the FISH-negative cases investigated. FISH analysis showed that BRAFrearrangements were diffusely present across tumor-rich areas in BRAF-fusion acinar-type neoplasms, which is consistent with an oncogenic driver alteration pattern. Thus, we demonstrated that, in comparison to targeted next-generation sequencing-based technologies, the FISH assay is highly sensitive and specific as well as time- and cost-efficient in the detection of BRAFfusions in acinar-type neoplasms. The FISH assay can be easily implemented in diagnostic settings to identify acinar-type neoplasms patients potentially suitable for targeted therapy to inhibit MAPK pathway activity.

Spitzoid neoplasms are a distinct group of melanocytic tumors. Genetically, they lack mutations in common melanoma-associated oncogenes. Recent studies have shown that spitzoid tumors may contain a variety of kinase fusions, including ROS1, NTRK1, ALK, BRAF, and RETfusions. We report herein the discovery of recurrent NTRK3gene rearrangements in childhood melanocytic neoplasms with spitzoid and/or atypical features, based on genome-wide copy number analysis by single-nucleotide polymorphism array, which showed intragenic copy number changes in NTRK3. Break-apart fluorescence in situhybridization confirmed the presence of NTRK3rearrangement, and a novel MYO5A-NTRK3transcript, representing an in-frame fusion of MYO5Aexon 32 to NTRK3exon 12, was identified using a rapid amplification of cDNA ends–based anchored multiplex PCR assay followed by next-generation sequencing. The predicted MYO5A-NTRK3 fusion protein consists of several N-terminal coiled-coil protein dimerization motifs encoded by MYO5Aand C-terminal tyrosine kinase domain encoded by NTRK3, which is consistent with the prototypical structure of TRK oncogenic fusions. Our study also demonstrates how array-based copy number analysis can be useful in discovering gene fusions associated with unbalanced genomic aberrations flanking the fusion points. Our findings add another potentially targetable kinase fusion to the list of oncogenic fusions in melanocytic tumors.

Microsatellite instability (MSI) and mismatch repair (MMR) deficiency represent a distinct oncogenic process and predict response to immune checkpoint inhibitors (ICIs). The clinicopathologic features of MSI-high (MSI-H) and MMR deficiency (MMR-D) in lung cancers remain poorly characterized.

Tocilizumab, a monoclonal antibody to interleukin-6 receptor, was recently approved for the treatment of moderate-to-severe rheumatoid arthritis. Two patients during clinical development met laboratory, but not clinical, criteria for Hy's law with bilirubin elevations suspected as a result of genetic variation in uridine diphosphoglucose glucuronosyltransferase (UGT1A1) typical of Gilbert syndrome.

Several kinase fusions are established targetable drivers in lung cancers. However, rapid and comprehensive detection remains challenging due to diverse partner genes and breakpoints. We assess the clinical utility and performance of a rapid microfluidic multiplex reverse transcription PCR-based assay for simultaneous query of fusions involving ALK, ROS1, RETand NTRK1/2/3,as well as METexon 14 skipping, using a three-hour automated process. Dual analytic strategies were utilized: fusion-specific amplification (FS) and 3’-5’ expression imbalance (EI). We analyzed 143 independent, formalin-fixed paraffin-embedded tumor samples (112 surgical specimens, 31 cytologic cell blocks); 133 with known kinase gene alterations and 10 negative samples based on clinically validated next-generation sequencing (NGS). Testing was successful in 142(99%) cases. The assay demonstrated a sensitivity of 97% (28/29), 100% (31/31), 92% (22/24), 81% (22/27) and 100% (20/20) for ALK, RET, ROS1, NTRK1/2/3rearrangements and METexon 14 skipping alterations, respectively, with 100% specificity for all. Concordant results were achieved in specimens aged up to 5 years, with >10% tumor, and inputs of at least 9 mm2(surgical specimens) and 9000 cells (cytologic cell blocks). The assay enables rapid screening for clinically actionable kinase alterations with quicker turnaround and lower tissue requirements compared to IHC and molecular methods, while also circumventing the infrastructure dependencies associated with NGS and FISH.

For patients with advanced NSCLC, cytologic samples may be the only diagnostic specimen available for molecular profiling. Although both rapid and comprehensive assessment are essential in this setting, an integrated multitest approach remains an important strategy in many laboratories, despite the risks and challenges when working with scant samples. In this study, we describe our experience and high success rate in using a multitest approach, focusing on the clinical validation and incorporation of ultrarapid EGFRtesting using the Idylla system followed by comprehensive next-generation sequencing (NGS).

Chromosomal rearrangements involving the neurotrophic receptor tyrosine kinases NTRK1-3produce oncogenic fusions in a wide variety of adult and pediatric cancers. Although the frequency of NTRKfusions in most cancers is <5%, efficacy in solid tumors harboring these fusions is striking with a 76% durable response rate recently reported with the highly selective pan-TRK inhibitor larotrectinib (LOXO-101) in a cohort comprised of 17 unique tumor types. By contrast, the frequency of NTRKfusions is not well appreciated in hematologic malignancies and targeting of NTRKfusions has not been clinically tested. Herein, we describe the occurrence of NTRKfusions across >7,000 patients with hematologic malignancies and characterize their signal transduction, transforming properties, and response to larotrectinib in vitroand in an AML patient and corresponding patient-derived xenograft (PDX) in vivo.