A process to reanalyze clinical DNA sequencing data for biomarker matching in the Lung-MAP Master Protocol.

For cancer clinical trials that require central confirmation of tumor genomic profiling, exhaustion of tissue from standard-of-care testing may prevent enrollment. For Lung-MAP, a master protocol that requires results from a defined centralized clinical trial assay to assign patients to a therapeutic substudy, we developed a process to repurpose existing commercial vendor raw genomic data for eligibility: genomic data reanalysis (GDR). Molecular results for substudy assignment were successfully generated for 369 of the first 374 patients (98.7%) using GDR for Lung-MAP, with a median time from request to result of 9 days. During the same period, 691 of 791 (87.4%) tissue samples received successfully yielded results, in a median of 14 days beyond sample acquisition. GDR is a scalable bioinformatic pipeline that expedites reanalysis of existing data for clinical trials in which validated integral biomarker testing is required for participation.

POU2AF3-rearranged sarcomas: A novel tumor defined by fusions of EWSR1 or FUS to a gene formerly designated COLCA2.

Gene fusions involving EWSR1 or FUS as the 5' partner have been reported in a diverse array of sarcomas. Here, we characterize the histopathology and genomics of six tumors harboring a gene fusion between EWSR1 or FUS and POU2AF3, an understudied, putative colorectal cancer predisposition gene. Striking morphologic features reminiscent of synovial sarcoma were observed including a biphasic appearance with variable fusiform to epithelioid cytomorphology and staghorn-type vasculature. RNA sequencing demonstrated variable breakpoints in EWSR1/FUS along with similar breakpoints in POU2AF3 that encompassed a 3' portion of this gene. For cases in which additional information was available, the behavior of these neoplasms was aggressive with local spread and/or distant metastases. Although further studies are needed to confirm the functional significance of our findings, POU2AF3 fusions to EWSR1 or FUS may define a novel type of POU2AF3-rearranged sarcomas with aggressive, malignant behavior.

Variable Landscape of PD-L1 Expression in Breast Carcinoma as Detected by the DAKO 22C3 Immunohistochemistry Assay.

BACKGROUND: In 2020, pembrolizumab was approved as a therapy for triple-negative breast cancer (TNBC) with the companion diagnostic DAKO 22C3 programmed death ligand-1 (PD-L1) immunohistochemistry assay. The study aimed to determine the landscape of PD-L1 expression as detected by the DAKO 22C3 PD-L1 assay in breast cancer subtypes and compare the clinicopathologic and genomic characteristics of PD-L1 positive and negative TNBC. METHODS: PD-L1 expression using the DAKO 22C3 antibody was scored using a combined positive score (CPS) and positive status was defined as CPS ≥10. Comprehensive genomic profiling was performed using the FoundationOne CDx assay. RESULTS: Of the 396 BC patients stained with DAKO 22C3, the majority were HR+/HER2- and TNBC (42% and 36%, respectively). Median PD-L1 expression and frequency of CPS ≥10 was highest in TNBC cases (median: 7.5, 50% CPS ≥10) and lowest in the HR+/HER2- group (median: 1.0, 15.5% CPS ≥10) (P < .0001). A comparison of PD-L1 positive and PD-L1 negative TNBC demonstrated no significant differences in clinicopathologic or genomic characteristics. TNBC tissue samples from the breast did have an observed enrichment for PD-L1 positivity compared to TNBC tissue samples from a metastatic site (57% vs. 44%), but this was not statistically significant (P = .1766). In the HR+/HER2- group, genomic alterations in TP53, CREBBP, and CCNE1 were more prevalent and genomic loss of heterozygosity was higher in the PD-L1(+) group compared to the PD-L1(-) group. CONCLUSIONS: The subtypes of breast cancer have distinct patterns of PD-L1 expression, supporting that further research of immunotherapies may include specific evaluation of optimum cutoffs for non-TNBC patients. In TNBC, PD-L1 positivity is not associated with other clinicopathologic or genomic features and should be integrated into future studies of immunotherapy efficacy.

Clinical and pathological features associated with circulating tumor DNA content in real-world patients with metastatic prostate cancer.

BACKGROUND: Liquid biopsy is a powerful tool that can enable treatment decisions for metastatic prostate cancer patients with difficult-to-biopsy tumors. However, the detection of genomic alterations via liquid biopsy is limited by the fraction (tumor fraction [TF]) of circulating tumor DNA (ctDNA) within the total cell-free DNA content. While prior work has preliminarily correlated TF with clinical features of prostate cancer, we sought to validate and provide additional resolution, such that a clinical practitioner might anticipate the probability of successful liquid biopsy profiling leveraging commonly assessed clinical and laboratory features. METHODS: A total of 813 liquid biopsy specimens were assessable, with 545 associated with a PSA prostate specific antigen measurement, collected in standard-of-care settings across approximately 280 US academic or community-based cancer clinics from September 2018 to July 2021. Deidentified data were captured into a real-world clinico-genomic database (CGDB). Comprehensive genomic profiling (CGP) was performed on extracted cell-free DNA from liquid biopsy samples. RESULTS: In multivariable models, higher PSA level, lower hemoglobin, lower albumin, higher alkaline phosphatase (all p < 0.001), and collection of liquid biopsy blood draw within 60 days of new treatment initiation (p = 0.002) were the most strongly associated features with higher TF. At PSA levels of <5 ng/ml, 43% of patients had a TF of <1% indicating an increased likelihood of unevaluable results. Conversely, at PSA levels of >5 ng/ml, 78% of patients had a TF of at least 1% and 46% had a TF of ≥10%, suggesting improved sensitivity for detection of targetable alterations. CONCLUSIONS: Universal genomic profiling of prostate cancers will require complementary use of liquid biopsy and tumor tissue profiling for suitable patients. The likelihood of adequate ctDNA shedding into plasma is one consideration when deciding whether to pursue CGP via liquid biopsy versus tumor profiling. Our real-world data suggest that PSA < 5 ng/ml is associated with lower ctDNA yield on liquid biopsy, potentially increasing the incidence of negative results or a need for confirmation with tissue testing.

Real-World Comprehensive Genomic Profiling Success Rates in Tissue and Liquid Prostate Carcinoma Specimens.

Challenges with sequencing tissue samples from patients with prostate cancer have been reported in clinical trials. To assess the success rate of comprehensive genomic profiling (CGP) for prostate cancer patients, we analyzed a real-world cohort who underwent sequencing of their prostate tissue sample as well as a subset of patients with a reflex liquid biopsy. Overall, a significant majority (82%) of tissue prostate carcinoma samples yielded reportable CGP results. Of those samples that were unsuccessful, most (75%) were inadequate samples that did not meet pre-established criteria to advance into sequencing. For cases where liquid CGP was performed if tissue CGP was unsuccessful, mutations that were likely attributable to prostate carcinoma were observed in most cases and all cases were successful in generating a report. These results suggest that, for CGP testing, prostate cancer tissue is a reasonable matrix type and that liquid samples can be effectively used as an alternative to tissue.

Clinicopathologic and Genomic Landscape of Non-Small Cell Lung Cancer Brain Metastases.

BACKGROUND: In patients with non-small cell lung cancer (NSCLC), 10%-40% will eventually develop brain metastases. We present the clinicopathologic, genomic, and biomarker landscape of a large cohort of NSCLC brain metastases (NSCLC-BM) samples. MATERIALS AND METHODS: We retrospectively analyzed 3035 NSCLC-BM tested with comprehensive genomic profiling (CGP) during routine clinical care. In addition, we compared the NSCLC-BM to a separate cohort of 7277 primary NSCLC (pNSCLC) specimens. Finally, we present data on 67 paired patients with NSCLC-BM and pNSCLC. RESULTS: Comprehensive genomic profiling analysis of the 3035 NSCLC-BMs found that the most frequent genomic alterations (GAs) were in the TP53, KRAS, CDKN2A, STK11, CDKN2B, EGFR, NKX2-1, RB1, MYC, and KEAP1 genes. In the NSCLC-BM cohort, there were significantly higher rates of several targetable GAs compared with pNSCLC, including ALK fusions, KRAS G12C mutations, and MET amplifications; and decreased frequency of MET exon14 skipping mutations (all P < .05). In the subset of NSCLC-BM (n = 1063) where concurrent PD-L1 immunohistochemistry (IHC) was performed, 54.7% of the patients with NSCLC-BM were eligible for pembrolizumab based on PD-L1 IHC (TPS ≥ 1), and 56.9% were eligible for pembrolizumab based on TMB-High status. In addition, in a series 67 paired pNSCLC and NSCLC-BM samples, 85.1% (57/67) had at least one additional GA discovered in the NSCLC-BM sample when compared with the pNSCLC sample. CONCLUSIONS: Herein, we defined the clinicopathologic, genomic, and biomarker landscape of a large cohort of patients with NSCLC-BM which can help inform study design of future clinical studies for patients with NSCLC with BM. In certain clinical situations, metastatic NSCLC brain tissue or cerebral spinal fluid specimens may be needed to fully optimize personalized treatment.

Variable Genomic Landscapes of Advanced Melanomas with Heavy Pigmentation.

BACKGROUND: In the current study, we examined the real-world prevalence of highly pigmented advanced melanomas (HPMel) and the clinicopathologic, genomic, and ICPI biomarker signatures of this class of tumors. MATERIALS AND METHODS: Our case archive of clinical melanoma samples for which the ordering physician requested testing for both PD-L1 immunohistochemistry (IHC) and comprehensive genomic profiling (CGP) was screened for HPMel cases, as well as for non-pigmented or lightly pigmented advanced melanoma cases (LPMel). RESULTS: Of the 1268 consecutive melanoma biopsies in our archive that had been submitted for PD-L1 IHC, 13.0% (165/1268) were HPMel and 87.0% (1103/1268) were LPMel. In the HPMel cohort, we saw a significantly lower tumor mutational burden (TMB, median 8.8 mutations/Mb) than in the LPMel group (11.4 mut/Mb), although there was substantial overlap. In examining characteristic secondary genomic alterations (GA), we found that the frequencies of GA in TERTp, CDKN2A, TP53, and PTEN were significantly lower in the HPMel cases than in LPMel. A higher rate of GA in CTNNB1, APC, PRKAR1A, and KIT was identified in the HPMel cohort compared with LPMel. CONCLUSIONS: In this study, we quantified the failure rates of melanoma samples for PD-L1 testing due to high melanin pigmentation and showed that CGP can be used in these patients to identify biomarkers that can guide treatment decisions for HPMel patients. Using this practical clinical definition for tumor pigmentation, our results indicate that HPMel are frequent at 13% of melanoma samples, and in general appear molecularly less developed, with a lower TMB and less frequent secondary GA of melanoma progression.

Activating IGF1R hotspot non-frameshift insertions define a novel, potentially targetable molecular subtype of adenoid cystic carcinoma.

Activation of the tyrosine kinase receptor IGF1R is targetable with existing tyrosine kinase inhibitors (TKIs) and monoclonal antibodies, but mutations in IGF1R have not been systematically characterized. Pan-cancer analysis of 326,911 tumors identified two distinct, activating non-frameshift insertion hotspots in IGF1R, which were significantly enriched in adenoid cystic carcinomas (ACCs). IGF1R alterations from 326,911 subjects were analyzed by variant effect prediction class, position within the gene, and cancer type. 6502 (2.0%) samples harbored one or more alterations in IGF1R. Two regions were enriched for non-frameshift insertions: codons 663-666 at the hinge region of the fibronectin type 3 domain and codons 1034-1049 in the tyrosine kinase domain. Hotspot insertions were highly enriched in ACCs (27.3-fold higher than in the remainder of the pan-cancer dataset; P = 2.3 × 10-17). Among salivary gland tumors, IGF1R hotspot insertions were entirely specific to ACCs. IGF1R alterations were most often mutually exclusive with other ACC drivers (9/15, 60%). Tumors with non-frameshift hotspot IGF1R insertions represent a novel, potentially targetable subtype of ACC. Additional studies are needed to determine whether these patients respond to existing IGF1R inhibitors.

Clinicopathologic and Genomic Landscape of Breast Carcinoma Brain Metastases.

BACKGROUND: Among patients with breast carcinoma who have metastatic disease, 15%-30% will eventually develop brain metastases. We examined the genomic landscape of a large cohort of patients with breast carcinoma brain metastases (BCBMs) and compared it with a cohort of patients with primary breast carcinomas (BCs). MATERIAL AND METHODS: We retrospectively analyzed 733 BCBMs tested with comprehensive genomic profiling (CGP) and compared them with 10,772 primary breast carcinomas (not-paired) specimens. For a subset of 16 triple-negative breast carcinoma (TNBC)-brain metastasis samples, programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC) was performed concurrently. RESULTS: A total of 733 consecutive BCBMs were analyzed. Compared with primary BCs, BCBMs were enriched for genomic alterations in TP53 (72.0%, 528/733), ERBB2 (25.6%, 188/733), RAD21 (14.1%, 103/733), NF1 (9.0%, 66/733), BRCA1 (7.8%, 57/733), and ESR1 (6.3%,46/733) (p < .05 for all comparisons). Immune checkpoint inhibitor biomarkers such as high tumor mutational burden (TMB-high; 16.2%, 119/733); high microsatellite instability (1.9%, 14/733); CD274 amplification (3.6%, 27/733); and apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like mutational signature (5.9%, 43/733) were significantly higher in the BCBM cohort compared with the primary BC cohort (p < .05 for all comparisons). When using both CGP and PD-L1 IHC, 37.5% (6/16) of patients with TNBC brain metastasis were eligible for atezolizumab based on PD-L1 IHC, and 18.8% (3/16) were eligible for pembrolizumab based on TMB-high status. CONCLUSION: We found a high prevalence of clinically relevant genomic alterations in patients with BCBM, suggesting that tissue acquisition (surgery) and/or cerebrospinal fluid for CGP in addition to CGP of the primary tumor may be clinically warranted. IMPLICATIONS FOR PRACTICE: This study found a high prevalence of clinically relevant genomic alterations in patients with breast carcinoma brain metastasis (BCBM), suggesting that tissue acquisition (surgery) and/or cerebrospinal fluid for comprehensive genomic profiling (CGP) in addition to CGP of the primary tumor may be clinically warranted. In addition, this study identified higher positive rates for FDA-approved immunotherapy biomarkers detected by CGP in patients with BCBM, opening a possibility of new on-label treatments. Last, this study noted limited correlation between tumor mutational burden and PD-L1 immunohistochemistry (IHC), which shows the importance of testing patients with triple-negative BCBM for immune checkpoint inhibitor eligibility with both PD-L1 IHC and CGP.

Expanding the spectrum of dicer1-associated sarcomas.

DICER1 syndrome is a hereditary cancer predisposition syndrome caused by deleterious germline DICER1 mutations. Characteristic "hotspot" somatic mutations of DICER1 have been identified in DICER1-associated tumors. With the exception of genitourinary embryonal rhabdomyosarcoma and anaplastic sarcoma of the kidney, sarcomas are rarely reported in DICER1 syndrome. Herein, we report the clinical, histopathologic, and molecular findings of a germline DICER1-associated ovarian sarcoma in a 5-year-old female, a somatic DICER1-associated metastatic peritoneal sarcoma in a 16-year-old female, and a somatic DICER1-associated primary intracranial sarcoma in a 4-year-old male. A comprehensive review of the literature, including 83 DICER1-associated sarcomas, illustrates an unequivocal histologic pattern mimicking pleuropulmonary blastoma, regardless of the site of origin. The features include undifferentiated small round blue cells, poorly differentiated spindle cells, and large bizarre pleomorphic cells (anaplasia), often with rhabdomyoblastic and/or chondroid differentiation, and rare bone/osteoid formation. This unique heterogeneous histologic pattern should raise suspicion for pathogenic DICER1 mutation(s) warranting a detailed review of the family history and DICER1 mutation analysis. In addition to expanding the phenotypic spectrum of DICER1-associated conditions, identification of pathogenic DICER1 variants facilitates optimized genetic counseling, caregiver education and judicious imaging-based surveillance.

Myeloid lineage switch following chimeric antigen receptor T-cell therapy in a patient with TCF3-ZNF384 fusion-positive B-lymphoblastic leukemia.

A pediatric patient diagnosed initially with B-lymphoblastic leukemia (B-ALL) relapsed with lineage switch to acute myeloid leukemia (AML) after chimeric antigen receptor T-cell (CAR-T) therapy and hematopoietic stem cell transplant. A TCF3-ZNF384 fusion was identified at diagnosis, persisted through B-ALL relapse, and was also present in the AML relapse cell population. ZNF384-rearrangements define a molecular subtype of B-ALL characterized by a pro-B-cell immunophenotype; furthermore, ZNF384-rearrangements are prevalent in mixed-phenotype acute leukemias. Lineage switch following CAR-T therapy has been described in patients with KMT2A (mixed lineage leukemia) rearrangements, but not previously in any patient with ZNF384 fusion.

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).

Pan-cancer Genomic Analysis of AXL Mutations Reveals a Novel, Recurrent, Functionally Activating AXL W451C Alteration Specific to Myxofibrosarcoma.

Myxofibrosarcoma (MFS) is a common soft tissue sarcoma of the elderly that typically shows low tumor mutational burden, with mutations in TP53 and in genes associated with cell cycle checkpoints ( RB1 , CDKN2A ). Unfortunately, no alterations or markers specific to MFS have been identified and, as a consequence, there are no effective targeted therapies. The receptor tyrosine kinase AXL, which drives cellular proliferation, is targetable by new antibody-based therapeutics. Expression of AXL messenger RNA is elevated in a variety of sarcoma types, with the highest levels reported in MFS, but the pathogenic significance of this finding remains unknown. To assess a role for AXL abnormalities in MFS, we undertook a search for AXL genomic alterations in a comprehensive genomic profiling database of 463,546 unique tumors (including 19,879 sarcomas, of which 315 were MFS) interrogated by targeted next-generation DNA and/or RNA sequencing. Notably, the only genomic alterations recurrent in a specific sarcoma subtype were AXL W451C (n = 8) and AXL W450C (n = 2) mutations. The tumors involved predominantly older adults (age: 44 to 81 [median: 72] y) and histologically showed epithelioid and spindle-shaped cells in a variably myxoid stroma, with 6 cases diagnosed as MFS, 3 as undifferentiated pleomorphic sarcoma (UPS), and 1 as low-grade sarcoma. The AXL W451C mutation was not identified in any non-sarcoma malignancy. A review of publicly available data sets revealed a single AXL W451C-mutant case of UPS that clustered with MFS/UPS by methylation profiling. Functional studies revealed a novel activation mechanism: the W451C mutation causes abnormal unregulated dimerization of the AXL receptor tyrosine kinase through disulfide bond formation between pairs of mutant proteins expressing ectopic cysteine residues. This dimerization triggers AXL autophosphorylation and activation of downstream ERK signaling. We further report sarcomas of diverse histologic subtypes with AXL gene amplifications, with the highest frequency of amplification identified in MFS cases without the W451C mutation. In summary, the activating AXL W451C mutation appears highly specific to MFS, with a novel mechanism to drive unregulated signaling. Moreover, AXL gene amplifications and messenger RNA overexpression are far more frequent in MFS than in other sarcoma subtypes. We conclude that these aberrations in AXL are distinct features of MFS and may aid diagnosis, as well as the selection of available targeted therapies.

Genomic landscape of 891 RET fusions detected across diverse solid tumor types.

In this study, we report the clinicopathologic and genomic profiles of 891 patients with RET fusion driven advanced solid tumors. All patient samples were tested using a tissue-based DNA hybrid capture next generation sequencing (NGS) assay and a subset of the samples were liquid biopsies tested using a liquid-based hybrid capture NGS assay. RET fusions were found in 523 patients with NSCLC and in 368 patients with other solid tumors. The two tumor types with the highest number of RET fusion were lung adenocarcinoma and thyroid papillary carcinoma, and they had a prevalence rate 1.14% (455/39,922) and 9.09% (109/1199), respectively. A total of 61 novel fusions were discovered in this pan-tumor cohort. The concordance of RET fusion detection across tumor types among tissue and liquid-based NGS was 100% (8/8) in patients with greater than 1% composite tumor fraction (cTF). Herein, we present the clinicopathologic and genomic landscape of a large cohort of RET fusion positive tumors and we observed that liquid biopsy-based NGS is highly sensitive for RET fusions at cTF ≥1%.

Predicting EGFR mutational status from pathology images using a real-world dataset.

Treatment of non-small cell lung cancer is increasingly biomarker driven with multiple genomic alterations, including those in the epidermal growth factor receptor (EGFR) gene, that benefit from targeted therapies. We developed a set of algorithms to assess EGFR status and morphology using a real-world advanced lung adenocarcinoma cohort of 2099 patients with hematoxylin and eosin (H&E) images exhibiting high morphological diversity and low tumor content relative to public datasets. The best performing EGFR algorithm was attention-based and achieved an area under the curve (AUC) of 0.870, a negative predictive value (NPV) of 0.954 and a positive predictive value (PPV) of 0.410 in a validation cohort reflecting the 15% prevalence of EGFR mutations in lung adenocarcinoma. The attention model outperformed a heuristic-based model focused exclusively on tumor regions, and we show that although the attention model also extracts signal primarily from tumor morphology, it extracts additional signal from non-tumor tissue regions. Further analysis of high-attention regions by pathologists showed associations of predicted EGFR negativity with solid growth patterns and higher peritumoral immune presence. This algorithm highlights the potential of deep learning tools to provide instantaneous rule-out screening for biomarker alterations and may help prioritize the use of scarce tissue for biomarker testing.

Method of Tissue Acquisition Affects Success of Comprehensive Genomic Profiling in Lung Cancer.

CONTEXT.­: Multiple procedural techniques can be used to obtain tissue to create a formalin-fixed, paraffin-embedded specimen for comprehensive genomic profiling (CGP) in lung cancer. The literature is mixed on whether the procedure affects CGP success. OBJECTIVE.­: To examine whether biopsy procedure affects lung cancer CGP success. DESIGN.­: This was a cross-sectional study of all patients with lung cancer whose specimens were submitted for CGP between January and February 2020. Multiple quality control metrics were used to determine whether cases were successfully profiled. RESULTS.­: In all, 3312 samples were identified. Overall, 67.5% (2236 of 3312) of samples were obtained from biopsies, 13.0% (432 of 3312) from fine-needle aspirations (FNAs), 9.7% (321 of 3312) from resections, 5.3% (174 of 3312) from fluid cytology cell blocks, and 4.5% (149 of 3312) from bone biopsies. Overall, 70.1% (2321 of 3312) of cases passed CGP, 15.4% (510 of 3312) of cases were released as qualified reports, and 14.5% (481 of 3312) of cases failed CGP. Resection samples were the most likely to be successfully sequenced, failing in only 2.8% (9 of 321) of instances, while fluid cytology specimens were the least likely, failing in 23.0% (40 of 174) of instances. Biopsy (14.5% [324 of 2236]), FNA (18.5% [80 of 432]), and bone biopsy (18.8% [28 of 149]) specimens failed at intermediate frequencies. On multivariate logistic regression analysis of CGP success on specimen type, fluid cytology (odds ratio [OR], 0.08; 95% CI, 0.03-0.19), biopsy (OR, 0.25; 95% CI, 0.11-0.52), FNA (OR, 0.14; 95% CI, 0.06-0.32), and bone biopsy (OR, 0.07; 95% CI, 0.03-0.17) specimens had decreased odds of CGP success relative to resection samples. Among patients with successfully sequenced samples, 48.0% were eligible for at least 1 therapy, based on a companion diagnostic or National Comprehensive Cancer Network biomarker. CONCLUSIONS.­: The method of tissue acquisition was an important preanalytic factor that determined whether a sample would be successfully sequenced and whether a clinically actionable genomic alteration would be detected.

Novel SOX10 indel mutations drive schwannomas through impaired transactivation of myelination gene programs.

BACKGROUND: Schwannomas are common peripheral nerve sheath tumors that can cause severe morbidity given their stereotypic intracranial and paraspinal locations. Similar to many solid tumors, schwannomas and other nerve sheath tumors are primarily thought to arise due to aberrant hyperactivation of the RAS growth factor signaling pathway. Here, we sought to further define the molecular pathogenesis of schwannomas. METHODS: We performed comprehensive genomic profiling on a cohort of 96 human schwannomas, as well as DNA methylation profiling on a subset. Functional studies including RNA sequencing, chromatin immunoprecipitation-DNA sequencing, electrophoretic mobility shift assay, and luciferase reporter assays were performed in a fetal glial cell model following transduction with wildtype and tumor-derived mutant isoforms of SOX10. RESULTS: We identified that nearly one-third of sporadic schwannomas lack alterations in known nerve sheath tumor genes and instead harbor novel recurrent in-frame insertion/deletion mutations in SOX10, which encodes a transcription factor responsible for controlling Schwann cell differentiation and myelination. SOX10 indel mutations were highly enriched in schwannomas arising from nonvestibular cranial nerves (eg facial, trigeminal, vagus) and were absent from vestibular nerve schwannomas driven by NF2 mutation. Functional studies revealed these SOX10 indel mutations have retained DNA binding capacity but impaired transactivation of glial differentiation and myelination gene programs. CONCLUSIONS: We thus speculate that SOX10 indel mutations drive a unique subtype of schwannomas by impeding proper differentiation of immature Schwann cells.

Cytoplasmic P53 Immunostaining With N-Terminus P53 Antibody And Absence Of Staining With C-Terminus P53 Antibody: A Report Of Two Pediatric Sarcomas With Distal Truncating TP53 Mutations Affecting Nuclear Localization Domain.

P53 immunohistochemical staining with antibodies targeted to epitopes at or near the N-terminus are commonly used in diagnostic pathology practice as a surrogate for TP53 mutations. The abnormal staining patterns indicating TP53 mutations include nuclear overexpression, null, and the recently described cytoplasmic staining. The latter staining pattern occurs with the less common TP53 mutations affecting its nuclear localization and/or tetramerization domains that are located toward the C-terminus. Here we describe the first two cases of pediatric sarcomas with cytoplasmic staining with P53 antibody against N-terminus epitope and the absence of staining with P53 antibody against C-terminus epitope. We propose that a more precise description of P53 immunohistochemical staining patterns should include the nature of the antibody used.

HPV51-associated Leiomyosarcoma: A Novel Class of TP53/RB1-Wildtype Tumor With Predilection for the Female Lower Reproductive Tract.

Inactivating mutations in tumor suppressor genes TP53 and RB1 are considered central drivers in leiomyosarcomas (LMSs). In high-risk human papillomavirus (HPV)-related tumors, a similar functional outcome is achieved through oncoproteins E6 and E7, which inactivate the p53 and RB1 proteins, respectively. Here, we hypothesized that HPV infection could provide an alternative mechanism for tumorigenesis in a subset of TP53/RB1-wildtype LMS. We evaluated tumor samples from 2585 consecutive unique patients carrying a diagnosis of gynecologic or soft tissue LMS. Tumor DNA and available RNA were analyzed by hybrid-capture-based next-generation sequencing/comprehensive genomic profiling of 406 genes and transcripts (FoundationOneHeme). Of the initial 2585 cases, we excluded 16 based on the presence of molecular alterations that are considered defining for sarcomas other than LMS. In the remaining 2569 cases, we searched for LMS that were TP53/RB1-wildtype (n=486 of 2569; 18.9%). We also searched LMS tumors for HPV sequences that we then classified into genotypes by de novo assembly of nonhuman sequencing reads followed by alignment to the RefSeq database. Among TP53/RB1-wildtype LMS, we identified 18 unique cases harboring HPV sequences. Surprisingly, most (n=11) were HPV51-positive, and these 11 represented all HPV51-positive tumors in our entire LMS database (n=11 of 2569; 0.4%). The absence of genomic alterations in TP53 or RB1 in HPV51-positive LMS represented a marked difference from HPV51-negative LMS (n=2558; 0% vs. 72% [P<0.00001], 0% vs. 53% [P=0.0002]). In addition, compared with HPV51-negative LMS, HPV51-positive LMS were significantly enriched for genomic alterations in ATRX (55% vs. 24%, P=0.027) and TSC1 (18% vs. 0.6%, P=0.0047). All HPV51-positive LMS were in women; median age was 54 years at surgery (range: 23 to 74 y). All known primary sites were from the gynecologic tract or adjacent anogenital area, including 5 cases of vaginal primary site. Histology was heterogeneous, with evaluable cases showing predominant epithelioid (n=5) and spindle (n=5) morphology. In situ hybridization confirmed the presence of high-risk HPV E6/E7 mRNA in tumor cells in three of three evaluable cases harboring HPV51 genomic sequences. Overall, in our pan-LMS analysis, HPV reads were identified in a subset of TP53/RB1-wildtype LMS. For all HPV51-associated LMS, the striking absence of any detectable TP53 or RB1 mutations and predilection for the female lower reproductive tract supports our hypothesis that high-risk HPV can be an alternative tumorigenic mechanism in this distinct class of LMS.