College Of American Pathologists Research Articles

Establishment and consistency verification of the standard operation procedure for laboratory detection of immunoglobulin G oligoclonal bands in cerebrospinal fluid

Objective: To establish the standard operation procedure (SOP) for detection of oligoclonal band (OCB) in cerebrospinal fluid (CSF) and verify consistency by using this SOP in different laboratories. Methods: The SOP for detection of CSF-OCB fluid was successfully established by an expert feedback approach. Neuroimmunology laboratories in 3 representative Chinese three-tier research hospitals were selected for this study, and commercially available protein electrophoresis automation systems and detection SOP were set up. The quality control product was provided by the College of American Pathologists (CAP) and Sebiacompany were used for interior quality and compared to each other, respectively. Seventeen serum and CSF paired samples were tested and compared using the same SOP. Kappa test or Kendall W test were adopted to evaluate the inter-laboratory consistency among different hospitals. Results: The results of repeated testings in a single hospital suggested that the 2-and 4-fold dilution for CSF-OCB were reported as positive, while 64-and 128-fold dilution were reported as negative. Positive or negative inconsistencies were reported in 8-, 16-, and 32-fold dilution. After increasing the number of repetitions, the results showed that both 16-and 32-fold dilution were reported as negative, and 8-fold dilution exhibited negative results (2 positive results for 40 repetitions, coincidence rate=95%).The results of multi-center inter-laboratory quality assessment showed that the detection consistency rate among 3 hospitals was 100% (Kappa value =1). Conclusions: The SOP to detect CSF-OCB established in this study demonstrates a good repeatability and stability. Therefore,such SOP would be a good reference for diagnostic laboratories to detect CSF-OCB in China.

Qatar Biobank in the COVID-19 era and beyond

Background: During the COVID-19 outbreak, Qatar Biobank (QBB) adapted its services to collect, process, and store high-quality data and specimens. This transformation period brought opportunities, risks, and challenges. Methods: QBB holds College of American Pathologists (CAP) accreditation and International Organization for Standardization (ISO) certification for Quality Management (9001:2105) and Information Security Management Systems (27001: 2013). These standards helped to effectively convert its operations to facilitate the COVID-19 national project. The COVID-19 Biorepository is a National Disease-based study aiming to collect adequate health information and biological samples from Qatar residents infected by SARS-CoV-2 virus to enable evidence-based research towards the discovery and development of novel healthcare interventions and to facilitate research projects related to the COVID-19 pandemic. QBB IT Department used open-source Onyx (ObiBa) software to newly develop a COVID-19 electronic system and interface for various clinical devices and Laboratory Information Management System. QBB operational services were adapted to accommodate the COVID-19 project by providing training to the personnel (n = 20; i.e. nurses, research assistants etc.) and developing work instructions (n>5) for the participants’ recruitment process, data and specimen collection in the different hospitals. A COVID-19 portal was also developed by QBB to facilitate data access for researchers from Qatar and worldwide. Results: Within 5 weeks QBB transformed to accommodate a disease/virus-based biorepository. At an operational level, multi-adjustments were implemented. QBB IT department developed an electronic system for the data collection and specimen traceability. Clinically trained staff were transferred to different healthcare facilities to recruit COVID-19 positive patients. QBB laboratory designed special collection kits. QBB Medical Review Office and Scientific and Education departments managed the recruitment process, set up of the study and provided training to the staff. The Communications and Participants Recruitment Department transformed its operations to fit the needs of the COVID-19 initiative. The Research Access Office designed the COVID-19 access portal and supported the project through purchasing of personal protective equipment and other administrative tasks. Conclusion: It is now time to consider lessons learned, as many countries have been affected by this pandemic, and to understand that biobanks are an asset for a country and there is a need to integrate them into a new standard with their sustainability in mind. Qatar Biobank is a good showcase of how a biobank can successfully assist in the collection of important data related to different health crises such as the COVID-19 pandemic.

Analytical validation of human epidermal growth factor receptor 2 immunohistochemistry by the use of the A0485 antibody versus the 4B5 antibody and breast versus gastric scoring guidelines in ovarian clear cell carcinoma.

The aim of this study was to evaluate human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) in ovarian clear cell carcinoma (OCCC) by using two antibodies and two scoring guidelines in correlation with HER2 amplification and clinicopathological features. A tissue microarray was constructed by use of a total of 71 OCCC cases for IHC (the A0485 antibody and the 4B5 antibody) and dual-colour silver in-situ hybridisation (DISH). Two pathologists independently scored the IHC according to the 2018 American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) breast cancer guidelines (breast guidelines) and the 2016 ASCO/CAP gastro-oesophageal adenocarcinoma guidelines (gastric guidelines). IHC concordances between A0485 and 4B5 were 87.3-93.0%. Three to 16 (4.2-22.5%) cases had an IHC score of 2+/3+ with frequent basolateral/lateral membranous staining. The 4B5 antibody yielded fewer IHC 2+ cases than the A0485 antibody (n=2-6 versus n=5-12). Five (7.0%) cases had HER2 amplification as determined with DISH. Cases with papillary-predominant growth patterns were significantly more likely to have HER2 amplification (P=0.0051). In predicting DISH results, IHC scored according to the gastric guidelines yielded 100%/100% sensitivity and 83.3-95.5%/98.2-100% specificity, and IHC scored according to the breast guidelines yielded 60-80%/33.3-66.7% sensitivity and 95.5-100%/100% specificity (including/excluding IHC 2+ cases). One case had intratumoral heterogeneity, with discordant results between primary and metastatic tumour specimens. We demonstrated HER2 amplification in 7% of OCCC cases, and the molecular change is significantly associated with papillary-predominant growth patterns. In predicting HER2 amplification, a combination of 4B5 IHC and gastric guidelines provides the best sensitivity and fewer equivocal (IHC 2+) cases. Given the intratumoral heterogeneity, assessment of HER2 status on whole tissue sections and on both primary and metastatic tumour specimens is recommended.

Adequacy of Surgical Pathology Reports of Colorectal Carcinoma and Its Significance.

IntroductionColorectal cancer is the fifth most common cancer in the world. For loco-regionally confined disease surgery is the definitive treatment. An adequate surgical pathology report is mandatory for the selection of adjuvant therapy. The objective of this study is to analyze whether adequate information is provided or not in the surgical pathology reports of colorectal carcinoma as according to College of American Pathologists (CAP) guidelines.MethodThis is a cross-sectional study carried out in the Department of Clinical Oncology, Jinnah Postgraduate Medical Center (JPMC) Karachi, tertiary care hospital in Pakistan. The duration of the study was from February 2020 to January 2021. A total of 153 surgical pathology reports issued by 11 different hospital-based laboratories after definitive surgery was assessed to look at its concordance rate with the checklist adapted from the CAP guidelines.ResultsOut of 153 surgical pathology reports, clinical information was provided in 72.5% of reports. Details of tumor extension were present in 88.2%, tumor margin in 75%, surgical procedure in 79%, and tumor deposits in 39.2% of reports. Macroscopic details including tumor perforation and evaluation of mesorectum were documented in 51.6% and 53.5% of the reports respectively. Details regarding perineural invasion along with lymphovascular invasion were present in 81.6% and 93% of the reports, respectively. The treatment effect was documented in only 25% of reports and regional lymph node status has been described in 85% of reports. Parameters described in all surgical pathology reports were: tumor site, tumor type, histologic type, and histologic grade. The pathological stage of the disease was documented in 91.5% of the reports.ConclusionThis study concluded that surgical pathology reports of the majority of pathology laboratories were not fully adhered to the checklist provided by the CAP guidelines. This will affect post-operative management along with the prediction of disease prognosis.

Liquid-Based Screening Tests Results: HPV, Liquid-Based Cytology, and P16/Ki67 Dual-Staining in Private-Based Opportunistic Cervical Cancer Screening.

The baseline data from the private-based opportunistic cervical cancer screening with HRHPV14, liquid-based cytology (LBC) and p16/Ki67 testing, and its quality assessment/quality control (QA/QC) tools are lacking. The age-stratified analysis of 30,066 screening tests results in a Polish population, including the investigation of HRHPV14 status, LBC, and p16/Ki67 dual-staining reporting rates, along with immediate histopathologic correlations, was conducted. For cytopathologic QA/QC, the College of American Pathologists (CAP) benchmarks and enhanced safety protocol were used. The NILM/ASC-US/LSIL/ASC-H/HSIL/AGC reporting rates were 93.9/3.4/2.0/0.22/0.24/0.11, respectively, with correlating HRHPV14-positive rates of 8.4/48.9/77.2/84.6/90.7/26.7. The reporting rates for HSIL (CIN2+) in HRHPV-positive women with NILM/ASC-US/LSIL/ASC-H/HSIL/AGC referred for a colposcopy with biopsy were 19.1/25.8/22.5/12.4/19.1/1.1% of the total HSIL (CIN2+). In total, of the 1130 p16/Ki67 tests, 30% were positive. In NILM HRHPV14-positive women with available histology result, HSIL(CIN2+) was detected in 28.3% of cases. In the first such large-scale Polish study presenting HRHPV14, informed LBC and HSIL (CIN2+) results, the reporting rates were highly consistent with data from American and other CAP-certified laboratories, confirming the possibility of using the 2019 ASCCP risk-based guidelines as one of the screening strategies outside of the US, in conditions of proper QA/QC. The private-based screening model can be effective in cervical cancer prevention, particularly in countries with low population coverage of public funds-based systems.

A retrospective audit to evaluate the appropriateness and rationalization of Fresh Frozen Plasma usage in a tertiary care hospital

BackgroundGeneral guidelines describing the potential indications and contraindications of Fresh Frozen Plasma (FFP) exist. However, their implementation is inadequate, leading to inappropriate use in various clinical settings. This study aims to define the appropriateness of the FFP usage in terms of therapeutic versus prophylactic indications. MethodsRetrospective audit was conducted over one year prior to and after an educational intervention (1122 patients for 6072 FFP units and 1061 patients for 4858 FFP units, respectively). Clinical diagnosis, indication for FFP transfusion, and coagulation profile were noted, and episodes of transfusion were divided into appropriate and inappropriate based on the guidelines of the British Committee for Standards in Hematology (2004 reviewed in 2018) and College of American Pathologists (1994). ResultsInitial audit found 51.8% of FFP transfusions to be inappropriate (3069 of 5922). Coagulation profile (with INR values less than 1.5 times of the normal) was the most common cause of inappropriate transfusion (15.08%). 56.7% of FFP were prophylactically transfused. Re-audit after educational interventions showed a 22.3% reduction in the number of inappropriate transfusions. ConclusionInappropriate, as well as high prophylactic usage of FFP, was noticed in the initial audit, which reduced significantly after educational interventions. Regular CMEs, interactive sessions with clinicians, functioning Hospital Transfusion Committees, and prospective audits can affirm, further improve and reinforce the existing Hospital Transfusion Guidelines.

Abstract 2194: Comparison of molecular profiling between Chinese cholangiocarcinoma and gallbladder cancer through next-generation sequencing

Abstract Background: Recently, some researchers proposed that molecular targeted therapies is ready for “prime time” in biliary tract cancer. However, few large-scale research data specifically analyze and compare the molecular characteristics of biliary tumors in the Chinese population. Here, we aim to report difference of molecular profiling of biliary tract cancers between Chinese cholangiocarcinoma (CCA) and gallbladder cancer (GCC) through next-generation sequencing, and summarize percentage of main targetable genetic alterations for CCA and GBC. Methods: Totally 1439 tumor sample of Chinese patient with biliary tract cancer were consecutively collected in China from January 2018 to July 2020, 907 patients were CCA, 532 were GCC. Gene mutation, microsatellite instability (MSI) were detected through next generation sequencing (NGS) by 3D Medicines, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). Results: The main mutational gene between CCA and GCC were compared, and results showed that the top ten gene mutation in CCA patients were TP53 (57.6%,522/907), KRAS (35.2%, 320/907), XRCC5 (27.7%, 251/907), CYP2D6 (26.8%,243/907), MDM2 (26.0%,236/907), MSH2 (25.7%,233/907), BLM/VEGFA (24.9%,226/907), POLD (24.7%,224/907), PRSS1 (23.6%,214/907), ATM (23.3%, 212/907). While top ten gene mutation in GCC group were TP53 (76.3%,406/532), MSH2 (43.0%,229/532), CYP2D6 (30.4%, 162/532), MDM2 (28.8%,153/532), VEGFA (27.6%,147/532), POLD1 (27.4%, 146/532), BLM (27.4%,146/532), ATM (25.6%,136/532), PRSS1 (25.2%,134/532), PRKDC (24.8%,132/532). In addition, percentage of the main targetable genetic alterations were also compared between CCA and GCC, such as IDH (5.7% vs 0.9%), FGFR (10.2% vs 10.7%), BRAF (5.1% vs 4.3%), PIK3CA (9.9% vs 14.8%), NTRK (7.4% vs 8.3%), ERBB2/3 (11.8% vs 24.8%), CDKN2A/2B(18.5% vs 23.9%), ARID1A(17.3% vs 17.7&), PTEN (10.3% vs 13.9%), MET (6.3% vs 7.3%), SMAD4 (14.6% vs 14.5%). Conclusion: Accurately understand the gene mutation characteristics of biliary tract tumors is required to make “Precision Medicine” a reality for the “majority” of patients diagnosed with biliary tract cancer. Chinese patients with CCA and GCC have different gene mutations, especially the proportion of mutant genes that are currently targetable. Therefore, different strategy should be performed for CCA and GCC patients. Citation Format: Chao Yu, Hushan Zhang, Jun Luo, Songling Zhao. Comparison of molecular profiling between Chinese cholangiocarcinoma and gallbladder cancer through next-generation sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2194.

UTILITY OF PANEL OF IMMUNO HISTOCHEMICAL MARKERS IN CARCINOMA BREAST-OUR EXPERIENCE IN A TERTIARY CARE HOSPITAL

Background: Breast cancer is the leading cause of malignancy in Indian females accounting for 16% of all malignancies. It causes lot of anxiety and emotional stress in the patient. Immunohistochemical panel of markers in breast carcinoma helps to categorize various tumour subtypes, gives valuable information on prognosis and also helps to determine, plan and predict response to therapy. Aims and Objectives: 1. To evaluate the expression of ER, PR, Her2neu, Ki67, CK5/6, EGFR in breast carcinoma to predict and plan therapy. 2. To categorize breast carcinoma based on molecular classication in our hospital. Materials and Methods: A prospective study of 278 cases of Breast Carcinoma obtained by trucut biopsy and Modied Radical mastectomy at Government Kilpauk Medical College was parafn processed and stained using hematoxylin and eosin. The lab reporting was done according to the standard system using College of American Pathologists (CAP) protocol. Immunohistochemistry was done using a panel of markers. Relevant demographic and clinical details of the patient were obtained and studied. Results: In the present study, breast carcinoma is commonly seen in the post menopausal age group. Invasive breast carcinoma (NOS type) is the most common histological variant. Grade 2 is the most common histological grade. Molecular testing showed most of the tumors belonged to Luminal A. CK5/6 and EGFR expression was high in Triple Negative Breast carcinomas. Conclusion: A thorough histomorphological and molecular studies help in understanding the tumour pathology and thereby providing prompt hormonal and targeted therapies improving the patient survival and prognosis.

Abstract 805: A germline mutation of gene ATM p.C1899* is associated with a family history of multiple cancers in a family in Yunnan province, China

Abstract Background: Ataxia-telangiectasia mutated (ATM) is a gene that plays role in cell cycle checkpoints and DNA damage response, heterozygous germline mutations in ATM are considered as one of risk factor of breast cancer (BC). There are also some reports that ATM mutations are related to other tumor types, such as prostate cancer. Several pathogenic germline mutations in ATM have been reported included missense mutations, nonsense mutations, frameshift deletions, in-frame deletion, large deletion. Here, we report a family history of multiple cancers related to germline mutation of ATM p.C1899* in a family in Yunnan province, China. Methods: The proband is a 58-year old male patient with colon cancer. Both tumor tissue samples and peripheral blood sample of the proband was subjected to next generation sequencing (NGS) analysis by 3D Medicines Inc., Shanghai, China, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). A novel germ-line mutation was identified, that was heterozygous ATM p.C1899* mutation (c.5697C>A). Peripheral blood sample of other family members have been collected and send to 3D Medicines Inc., for NGS analysis. Results: In total of 6 members of the family underwent NGS analysis, results showed that these members were carry a germline mutation of gene ATM p.C1899*, one uncle was patient with gastric cancer, and one aunt was patient with pancreatic cancer, which means this germline mutation was related with three different cancer in a family. Conclusion: The mutation of ATM, especially germline mutation, may associated with multiple cancers, such as gastric cancer, colorectal cancer and pancreatic cancer. Accurate genetic testing should be given more attention to better control the risk of familial cancer. Citation Format: Xianghua Sun, Hushan Zhang, Wanfu Zhang, Zhiping Zhang, Bo Li. A germline mutation of gene ATM p.C1899* is associated with a family history of multiple cancers in a family in Yunnan province, China [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 805.

Abstract 2193: Analysis of oncologic characteristics of penile cancer

Abstract Background: Penile cancer is a rare malignant tumor characterized by invasive growth and early metastasis. Several risk factors related to penile cancer have been identified, such as human papillomavirus status (HPV), circumcision status, smoking, poor hygiene. Current scientific evidence and guidelines on the management and treatment of penile cancer are rarely updated. In particular, there is insufficient evidence for targeted therapy and immunotherapy for penile cancer. Here, we analyzed features of gene profiling of penile cancer and some biomarkers of immunotherapy such as tumor mutation burden (TMB), PD-L1 expression, and status of microsatellite. Methods: Totally 26 tumor samples of Chinese patients with penile cancer were consecutively collected in China from January 2018 to June 2020, Next generation sequencing (NGS) was used to detect gene mutation, microsatellite instability (MSI) or microsatellite stable (MSS), and tumor mutational burden (TMB) analyzed by a 733 gene panel by 3D Medicines, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). PD-L1 expression detected by using Dako PD-L1 IHC 22C3 pharmDx, Tumor Proportion Score (TPS) was used to determine expression of PD-L1. TPS was arranged into the following intervals: strong positive ≥50%, moderate positive ≥5% and <50%, weak positive ≥1% and <5%, and negative <1%. Results: Among these 26 samples, 20 samples were available for TMB analysis and MSI/MSS analysis, and 15 samples were available for analysis of PD-L1 expression. The average TMB level of these penile cancer was 7.4 mutants/Mb, and 85% (17/20) of them with TMB level under 10 mutants/Mb. Analysis of PD-L1 expression results showed that 26.7% (4/15) with PD-L1 negative, 6.7% (1/15) weak positive, 53.3% (8/15) moderate positive, 13.3%(2/15) with PD-L1 strong positive. In addition, none of these sample were MSI. Furthermore, NGS results show that a total of 176 gene mutations have been identified in these 26 Chinese patients with penile cancer, and 43.2% (73/176) were germline mutation. The main mutated gene were TP53 (65.4%,17/26), CDKN2A (50.0%,13/26), AKT (46.2%,12/26), FAT1 (38.5%,10/26), PIK3CA/MSH2/POLD1/VEGFA (34.6%, 9/26), BRIP1/MDM2/ATM/XPC/TERT (30.8%,8/26). The top ten of germline mutated genes were AKT (42.3, 11/26), XPA (38.5%,10/26), POLD1 (34.6%, 9/26), ERCC2/TP53/RAC1/MSH2/MSH3/ATM/VEGFA/PRKDC/MGMT/BLM/MDM2/BRIP1/PRSS1/ERCC5 (30.5%,8/26). Conclusion: Patients with penile cancer have rich spectrum of gene mutations, especially, high percentage of germline mutation was displayed in penile cancer, it may suggest that genetic/Familial high-risk should be put into consideration in the management of penile cancer. What's more, immunotherapy may also have certain potential because of the expressing of PD-L1. Citation Format: Bin Zhao, Hushan Zhang, Guoying Zhang, Jian Xu, Maolin Yang. Analysis of oncologic characteristics of penile cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2193.

Abstract 2219: Analysis of gene landscape of small cell lung cancer of Chinese through next-generation sequencing

Abstract Background: As the more malignant subtype of lung cancer, small cell lung cancer (SCLC) displayed more aggressive and worse prognosis. Standard treatments have rarely changed in decades, therefore, in recent years, there have been attempts to explore targeted therapy and even immunotherapy. However, SCLC has more challenging targets. It was reported that almost 100% of SCLC has p53 and Rb mutations, and also has functional changes in Myc. Here we report some data about gene mutation of SCLC of Chinese patients. Methods: Tumor samples of 410 SCLC patients were consecutively collected in China from July 2018 to May 2020, next generation sequencing (NGS) was performed to detect gene mutation, and tumor mutational burden (TMB) measured by a 733 gene panel. PD-L1 expression detected by using Dako PD-L1 IHC 22C3 pharmDx, Tumor Proportion Score (TPS) was used to determine expression of PD-L1. TPS was arranged into the following intervals: strong positive ≥50%, moderate positive ≥5% and <50%, weak positive ≥1% and <5%, and negative <1%. All these were performed by 3D Medicines, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). Results: NGS results showed that the top gene mutation in these 410 Chinese SCLC patients were TP53 (88.0%,361/410), RB1(63.9%,262/410), BRCA1/2(34.0%,139/410), LRP1B(28.3%,116/410), FAM135B(24.1%,99/410), PIK3CA(23.9%,98/410), CYP2D6(21.0%,86/410), POLA1(20.2%,83/410), NTRK1(19.5%,80/410), MSH2(19.3%,79/410), ATM(19.3%,79/410), AKT2(18.8%,77/410), VEGFA(18.8%,77/410). Furthermore, 159 samples available for TMB analysis, and results showed that the average TMB level was 11.7 mutants/Mb, and 49.7%(79/159) were higher than 10 mutants/Mb, and 50.3%(80/159) were under 10mutants/Mb. In addition, 167 samples available for PD-L1 analysis, and results showed that 86.8% (145/167) with PD-L1 negative, 7.8(13/167) moderate positive, none with PD-L1 strong positive. Conclusion: Chinese patients with SCLC have rich spectrum of gene mutations, it suggests that targeted therapy should also have certain potential. In addition, about half of SCLCs have a TMB level above 10mutants/Mb, and immunotherapy should been considered more in the future treatment for Chinese SCLC patients. Citation Format: Jing Zhang, Hushan Zhang, Feng Ling, Yuanhan Wang, Long Li, Song Yang. Analysis of gene landscape of small cell lung cancer of Chinese through next-generation sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2219.

Abstract 2253: Comparison of genomic alterations in neuroendocrine tumors originated from different primary sites

Abstract Background: Neuroendocrine tumors (NETs) are heterogeneous, relatively rare tumors derive from neuroendocrine system. Currently, limited therapeutic strategies are available for NETs. Next-generation sequencing (NGS) and target gene-based precision therapy have shown promising efficacy in many tumors, but fare in NETs. Several reports illustrated that the primary sites of NETs were significantly bound up with the clinical response and prognosis. However, characteristics of their genomic alterations are insufficiency nowadays. Methods: A cohort of 94 Chinese NET patients were recruited, and the FFPE tumor tissues and matching blood samples from different primary sites were collected. Targeted next generation sequencing (NGS) of 450 genes was performed in OrigiMed (Shanghai, China) with a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Results: In all patients, the top 5 most-frequently aberrant genes were TP53 (46.8%, 44/94), RB1 (23.4% 22/94), MEN1 (20.2%, 19/94), KRAS (11.7%, 11/94) and ATRX (9.6%, 9/94). The enrolled NETs contain 7 different primary sites, namely, 37 pancreatic NETs (PNETs), 16 hepatic NETs (HNETs), 11 gastric NETs (GNETs), 10 gallbladder NETs (GB-NETs), 8 esophageal NETs (ENETs), 7 colorectal NETs (CNETs), and 5 small intestine NETs (SI-NETs). Based on origin sites, TP53 is the most widely distributed mutant gene in all sites except for PNETs (Ranked 3rd), while RB1 mutations were significantly higher in ENETs (75.0%, 6/8), GB-NETs (60.0%, 6/10) and GNETs (36.4%, 4/11). Other higher -frequency mutated genes among different sites showed greatly dissimilarity (MEN1, ATRX and DAXX in PNETs; FAT3, MAX, MUC16, GATA4 and OBSCN in HNETs; APC, KRAS and PTEN in GNETs; TERT, ERBB2 and YES1 in GB-NETs; LRP1B and FBXW7 in ENETs; APC, ADGRA2 and FGFR1 in CNETs; NF1 in SI-NETs). Furthermore, signaling pathways involved in potential drug-target genes were analyzed. Results revealed 16.0% (15/94) patients with aberrations in PI3K/AKT/mTOR pathway, 11.7% (11/94) in Cell-Cycle pathway, 9.6% (9/94) in HRD pathway, 9.6% (9/94) in FGF pathway and 16.0% (15/94) in other cancer-related genes (ERBB2, VHL, MET etc.). Conclusions: This study reveals the genomic alteration characteristics of NETs from different primary sites. The profiles obtained in our study may provide evidences for further targeted therapy to improve outcomes of Chinese NETs. Citation Format: Qiyun Tang, Ye Tian, Xiaolin Li, Jian'an Bai, Min Liu, Ping Hu, Shanshan Zhang, Zanmei Xu, Yueting Qu, Aodi Wang. Comparison of genomic alterations in neuroendocrine tumors originated from different primary sites [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2253.

Abstract 2184: Gene characteristics of Chinese patients with small bowel cancer

Abstract Background: Small bowel cancer is a rare malignancy which account for only 1-3% of all malignant gastrointestinal tumors. Herein, we aim to provide an overview of gene characteristics of Chinese patients with small bowel cancer based on the location of the tumor in the small bowel. Methods: Tumor samples of 324 Chinese patients with small bowel cancer were consecutively collected in China from February 2018 to May 2020, among them, 289 patients with cancer located in duodenum (group 1), 35 patients with cancer located in the other region of small bowel (group 2). Next generation sequencing (NGS) was performed to detect gene mutation, microsatellite instability (MSI), and tumor mutational burden (TMB) measured by a 733 gene panel by 3D Medicines, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). Results: NGS results revealed that the main mutated genes were different between two groups, in detail, the top ten gene mutation in group 1 were TP53 (51.4%,18/35), KRAS (45.7%, 16/35), APC (34.3%, 12/35), POLE (20.0%,7/35), PIK3CA/POLD1/MSH2 (17.1%,6/35), mTOR/PRSS1/LPR1B/BRCA1/SMAD4 (14.3%,5/35). While top ten gene mutation in group 2 were TP53 (66.4%,192/289), KRAS (49.8%, 144/289), ERCC1 (38.8%, 112/289), UGT1A1 (31.5%, 91/289), APC (29.4%, 85/289), BRCA1 (28.7%,83/289), AKT2 (27.3%, 79/289).In addition, TMB level and percentage of MSI-H were also compared between the two groups. 12 patients were available for TMB analysis in group 1, 59 for group 2, the average TMB level in two groups were 23.84 mutants/Mb and 7.8 mutants/Mb, respectively. 50%(6/12) and 11.8%(7/59) were under 10 mutants/Mb in two groups. What's more, the percentage of MSI-H in two groups were 16.7% (5/30) and 3.2% (8/243). Conclusion: Patients with cancer located in duodenum patients with cancer located in the other region of small bowel displayed obvious difference in gene landscape, this imply that these patients should be treated differently. Citation Format: Quan Zhao, Hushan Zhang, Zhuyun Lei, Jianing Sheng, Dun Xiong. Gene characteristics of Chinese patients with small bowel cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2184.

Abstract 2660: The gene mutation profile in HCC patients with different AFP levels at diagnosis

Abstract Background: Alpha-fetoprotein (AFP) blood level in Hepatocellular carcinoma (HCC)is an important marker widely used in clinical practice. Although different AFP levels indicate the different prognosis of HCC patients, the gene mutation profile is still unclear. The research was to conduct a comprehensive study of the gene mutation profile in HCC patients with different AFP levels at diagnosis. Methods: Retrospective analysis was carried out on medical records of HCC patients who had received a hepatectomy between January 2016 and December 2018. Formalin-fixed, paraffin-embedded (FFPE) HCC tissues and matched blood samples were collected for targeted next-generation sequencing (NGS) assay at OrigiMed (Shanghai, China), a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Genomic variants including single nucleotide variations (SNV), short/long insertion/deletions (Indel), copy number alterations and gene rearrangements were analyzed. Results: A total of 180 HCC cases were enrolled in the study. The patients were categorized into AFP<10ng/ml (n=63) group, 10ng/ml≤AFP<1000ng/ml (n=71) group, and AFP≥1000ng/ml (n=46) group. The higher AFP level at diagnosis was positively correlated with younger incidence age (P=0.012), lower blood glucose (P=0.008), larger diameter of tumor nodules (P=0.006), more microvascular invasion (P=0.01), higher grade of tumor differentiation (P<0.001), poorer overall survival (P=0.023), and recurrence free survival (P=0.007). AXIN1 mutation frequency significantly increased with the rise of the APF level: AFP<10ng/ml (7.9%), 10ng/ml≤AFP<1000ng/ml (25.4%), and AFP≥1000ng/ml (42.2%, P<0.001), while TP53 mutation frequency decreased with the rise of the AFP level: AFP<10ng/ml (65.1%), 10ng/ml≤AFP<1000ng/ml (57.7%), and AFP≥1000ng/ml (48.9%) with only near significance (P=0.095) among three groups. Furthermore, we identified 11q13 (FGF3, FGF4, FGF19, CCND1) amplification frequency increased with AFP level: AFP<10ng/ml 4.8%, 10ng/ml≤AFP<1000ng/ml 12.7%, and AFP≥1000ng/ml 20.9%, P=0.015. Conclusion: We demonstrated AXIN1 mutation frequency increased with the rise of the AFP level. Because these AXIN1 mutations can result in inactivating the AXIN1 protein and the AXIN1 is a known negative regulator of the Wnt/β-catenin signaling pathway, we reason that the Wnt/β-catenin signaling pathway has a deleterious effect on the poor prognosis in the higher AFP groups, and/or directly on the rise of the AFP level. Citation Format: Xiang Kui, Liqun Wu, Yang Ke, Yan Wang, Hai Li, Juan Zhao, Tingting He, Lin Wang. The gene mutation profile in HCC patients with different AFP levels at diagnosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2660.

Abstract 2228: Usage of ctDNA analysis to identify alterations with strong evidence for response or resistance to targeted therapy in patients with NENs

Abstract Background: Neuroendocrine neoplasias (NENs) are a heterogeneous group of rare tumors scattered throughout the body. For nonresectable advanced NENs, the main treatment approaches including somatostatin analog, multiple TKIs, mTOR inhibitors and peptide receptor radionuclide therapy, whereas platinum-based chemotherapy is the main treatment for advanced high-grade and poorly differentiated NECs. Currently, there is no standard second-line treatment for NECs when disease progression. ctDNA as a non-invasive diagnostic avenue, which might potentially provide treatment guidance in NENs. Methods: We queried consecutive data from 40 NENs patients who underwent a targeted next-generation sequencing (NGS) assay performed by 3DMed Clinical Laboratory Inc., a College of American Pathologists (CAP) certified and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory of 3D Medicines Inc. between January, 2017 and June, 2020 in China, to identify the alterations detected in ctDNA. The alterations were classified based on the ranking in the OncoKB database as of January 2020. Results: In total, 40 of NENs patients detected with at least one alteration in ctDNA. The median age was 54 years, including 28 males and 12 females. Overall, 40.0% of patients had a Level 1 alteration, 22.5% of patients had a Level 2 alteration, and 22.5% of patients had a R1 alteration (selected alterations were outlined in Table). Conclusion: ctDNA analysis could provide information of alterations with strong evidence for targeted therapy or drug resistance based on the OncoKB database classification for NENs. Though the alterations are associated with other specific cancer types, the alterations still illustrate a part of NENs patients might have chance to be benefited from targeted therapy. AlterationsNumber of patients (%)Total Level 1 Alterations16 (40.0%)PIK3CA7 (17.5%)BRAF V600E2 (5.0%)BRCA22 (5.0%)MSI-H1 (2.5%)Total Level 2 Alterations9 (22.5%)ERBB2 activating4 (10.0%)MET amplication1 (2.5%)Total Level R1 alterations9 (22.5%)KRAS mut9 (22.5%) Citation Format: Kunli Du, Xueke She, Depei Huang, Xudong Shen, Hushan Zhang, Jianyong Zheng. Usage of ctDNA analysis to identify alterations with strong evidence for response or resistance to targeted therapy in patients with NENs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2228.

Abstract 2659: Genomic profiling of Chinese adenosquamous carcinoma of the pancreas

Abstract Background: Adenosquamous carcinoma of the pancreas (PASC) is a mixed tumor type which contains squamous cell carcinoma and also ductal adenocarcinoma components. PASC is a rare type representing about 1-4% of the total incidence. Due to the rarity of this malignancy, limited genomic data have been performed. In this study, we analyzed the genomic alterations and clinical signatures of PASC. Materials and Methods: Formalin fixed, paraffin embedded (FFPE) tumor tissues and matched blood samples were collected for targeted next-generation sequencing (NGS) assay at OrigiMed (Shanghai, China), a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Genomic alterations including single base substitution, indel, copy number variations, gene fusions and rearrangement were assessed. Tumor mutational burden (TMB) was also analyzed by NGS algorithm. Alterations in homologous recombination repair (HRR) with PASC were analyzed. Results: In total, 31 PASC patients were recruited included 15 females (48.4%) and 16 males (51.6%) with a media age of 59 years old (range 35-78). A total of 32% (10/31) of patients possessed a confirmed cancer-related family history. The most commonly altered genes were KRAS (97%), TP53 (77%), CDKN2A (35%), SMAD4 (23%), FAT3 (13%), CIC (10%) and SPTA1 (10%). The KEGG pathway analysis revealed that those top mutated genes significantly associated with MAPK signaling pathway. 42% (13/31) of the patients had one or more actionable genomic alterations, including BRCA2, STK11, CDKN2A/B, FGFR and PTEN. Germline mutations were identified in 4 patients (13%), including BRCA2 (2/4), SPINK1 (1/4), FANCA (1/4). The most common mutational type was substitution/Indel (56%), followed by truncation (20%) and gene amplification (17%). Three (10%) patients had at least one mutation in HRR genes, including BRCA2 (2/3) and CHEK2 (1/3).The median TMB of patients with PASC was 3.2 muts/Mb (range, 0.5-9.3 muts/Mb). Patients with STK11 alterations had lower value of TMB than STK11 wild type (median TMB 0.85 vs. 3.37 muts/Mb, respectively, P <0.05). In addition, patients with HRR mutations had a significantly higher TMB value than HRR wild type (7.73 vs. 2.73 muts/Mb, respectively, P <0.01). Conclusion: Our study revealed the genomic profiling of the largest sample size of Chinese PASC patients so far. 42% (13/31) of the patients had one or more actionable genomic alterations. HRR pathway alterations are relatively frequent (10%) in PASC and consideration for biomarker-enriched clinical trials with PARP, immune checkpoint inhibitors, and novel combinations are warranted. Citation Format: Zheng Wang, Xue Yang, Wei Li, Zheng Wu, Qingyong Ma, Xiaofang Qi, Juan Zhao. Genomic profiling of Chinese adenosquamous carcinoma of the pancreas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2659.

Abstract 2229: Landscape of RB1 alterations in 22,432 Chinese solid tumor patients

Abstract Background: The retinoblastoma susceptibility gene (RB1) is one of tumor suppressor genes. This gene is mutated at variable frequencies in a variety of other human cancers. Cancer genome sequencing revealed that most types of cancer with RB1 mutation were retinoblastomas, osteosarcomas, and small-cell lung cancers, and its mutation was also found in other cancer types with a lower frequency, for instance, prostate cancer, breast cancer and etc. RB1 protein plays a prominent role in a variety of molecular processes related to DNA including gene transcription, DNA replication, DNA repair, and mitosis. However, no comprehensive status of RB1 alterations in Chinese populations with solid tumor has been reported yet. Methods: The Formalin-Fixed Paraffin-Embedded (FFPE) tissues from solid tumor patients who have underwent next-generation sequencing (NGS) from January 01, 2017 to April 15, 2020 in 3DMed Clinical Laboratory Inc. (a College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory) were analyzed. The diagnosis of the tissues was confirmed by hematoxylin and eosin (H&E) staining. The single nucleotide variants (SNVs), copy number variants (CNVs) and gene rearrangements data of these patients were analyzed. Results: Of 22,432 Chinese solid tumor patients with more than 20 tumor types (58% males and 42% females, with median age was 60 years), genomic alterations in RB1 were observed in 1712 (7.6%) patients. RB1 mutations occurred most frequently in small cell lung cancer (138/165, 83.6%), followed by neuroendocrine neoplasms (42/170, 24.7%), sarcoma (127/554, 22.9%), biliary tract cancer (40/209, 19.1%), head and neck cancer (4/22, 18.2%), and liver cancer (232/1649, 14.1%). And (185/1712, 10.8%) patients were detected with germline RB1 mutation. When stratified by the mutational types, 1,443 (6.4%) patients were with SNVs, 59 (0.3%) with fusions, and 210 (0.9%) with loss in RB1 gene. Conclusion: Our results suggested RB1 alteration was widely occurred in solid tumor patients in China, and specific alteration rates differed largely between tumor types. Our study also suggested usage of NGS in the need for individualized characterization of cancers and further investigations are warranted for the cancer treatment upon molecular profiling in the clinical therapeutic setting. Citation Format: Nan Wang, Xueke She, Depei Huang, Xudong Shen, Hushan Zhang, Gang Ji. Landscape of RB1 alterations in 22,432 Chinese solid tumor patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2229.

Abstract 2179: Identification of ROS1 alterations in ctDNA from colorectal cancer patients in China

Abstract Background: ROS proto-oncogene 1 (ROS1) is an oncogenic driver involved in various cancer types for which has FDA approved therapies. ROS1 has shown to undergo genetic rearrangements in a variety of human cancers including glioblastoma, non-small cell lung cancer (NSCLC), ovarian cancer, gastric adenocarcinoma and colorectal cancer. The rearrangements create fusion proteins in which the kinase domain of ROS1 becomes constitutively active and drives cellular proliferation. Although previous data have reported ROS1 fusions occur in 0.2% to 2.4% of colorectal cancers, the frequency and type of ROS1 alterations in Chinese CRC patients have not been fully reported. Methods: This study queried data from 1,083 colorectal cancer samples which underwent a targeted next-generation sequencing assay performed by 3DMed Clinical Laboratory Inc., a College of American Pathologists (CAP) certified and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory of 3D Medicines Inc. between January, 2017 and June, 2020 in China, to identify the incidence of ROS1 alterations detected in ctDNA in colorectal cancer patients. The detected genetic alteration types included single-nucleotide variants (SNVs), copy number variations (CNVs) and gene rearrangements/fusions. Results: ROS1 alterations were found in 114 patients among the 1,083 (10.5%) CRC patients' cohort, including 72 males and 42 females, median age was 58 years old. The ROS1 alterations included 110 (96.5%) SNVs, 3 (2.6%) CNVs and 1 (0.9%) GOPC-ROS1 fusion. Among the 110 single nucleotide variants, we identified 91 (82.7%) of ROS1 SNVs were nonsynonymous mutations. The top 5 co-occurring mutations in samples with ROS1 alterations were TP53 (71, 62.2%), CYP2C19 (48, 42.1%), APC (48, 42.1%), KRAS (46, 40.3%) and DPYD (42, 36.8%). Conclusion: Our study indicated that ctDNA can be used as a nonvasive methodology to detect cancer-specific genetic aberrations in plasma for CRC. ROS1 alterations occurred modestly in Chinese colorectal cancer patients. Co-occurring mutations may provide different biological subsets of patients with ROS1-mutant colorectal cancer to reveal patient outcomes and response to therapy. Further investigation could be focused on the effect of ROS1 nonsynonymous mutations on the ROS1 proteins in vitro to identify whether these are more actionable than currently recognized. Citation Format: Mojin Wang, Lili Zhu, Depei Huang, Xudong Shen, Hushan Zhang, Xueke She. Identification of ROS1 alterations in ctDNA from colorectal cancer patients in China [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2179.

Abstract 2283: Validation & application of next-generation sequencing panel YuanSu S for gene rearrangements/fusions detection

Abstract Introduction: Gene rearrangement/fusion play an important role in cancer diagnosis and treatment. Comparing with routine diagnostic methods, Sanger sequencing, fluorescence in situ hybridization (FISH) & immunohistochemistry (IHC), next-generation sequencing (NGS)-based panel can provide genetic information with robust sensitivity and precision. Moreover, panel-based RNAseq can detect novel fusions and only requires a small amount of RNA. We have developed a 450-gene DNA & RNA NGS panel, YuanSu S, for clinical sample detection. In this study, YuanSu S was applied to detect gene rearrangements/fusions and determine its limit of detection (LOD) and concordance with FISH/IHC, and difference between DNAseq & RNAseq. Methods: A total of 184 formalin fixed and paraffin embedded (FFPE) sarcoma samples were detected by YuanSu S at OrigiMed, a laboratory certified by College of American Pathologists (CAP) & Clinical Laboratory Improvement Amendments (CLIA). Gene fusions were analyzed by OriFusion, an OrigiMed's proprietary algorithm. For LOD determination, gradient amounts of RNA or mixed cell line samples were processed for sequencing. To confirm its concordance with FISH/IHC, 36 sarcomas FFPE samples were examined by FISH (33/36) or IHC (3/36). A cohort of 148 tumor samples was used to analyze rearrangement/fusion detection capability. Results: For RNAseq in YuanSu S, LOD was determined as 5 copies/1ng RNA input and was verified by ddPCR. Samples with rearrangement/fusion ≥ 5% detected by DNAseq were confirmed by ddPCR. For the interfering substance validation, results of samples treated with ethanol or necrotic tissue were consistent with untreated samples. Furthermore, two different Illumina platforms, Nextseq 500 & Novaseq 6000, showed no difference in sequencing abilities. 36 sarcoma FFPE samples were assessed by NGS and verified by FISH or IHC. All the 19 samples with FISH or IHC positive were detected the same rearrangements/fusions by YuanSu S, whereas the negative samples had no fusion detected. In the cohort of 148 samples, 426 rearrangements/fusions were detected by YuanSu S. 101 (23.7%) were detected both by DNAseq & RNAseq; 204 (47.9%) were determined by DNAseq only; while 121 (28.4%) were determined by RNAseq only. Rearrangements were detected by DNAseq in 97 (65.5%) samples, and 40 (41.2%) may benefit from FDA-approved drugs. Importantly, 51 (34.5%) samples had fusions detected only by RNAseq, and 33 (64.7%) may benefit from targeted therapies. Conclusion: Our results confirmed the reliability and advantages of YuanSu S, a DNA plus RNA NGS panel. Experience from YuanSu S indicated that integrative DNA & RNA sequencing could increase sensitivity of fusion detection. Therefore, the combination of DNAseq & RNAseq is able to screen more patients carrying fusion targets who could benefit from corresponding inhibitors and play an important role in guiding treatment decisions. Citation Format: Jiacheng Cai, Feng Li, Haiyan Wu, Weifeng Wang, Qiuyue Pan, Lin Zhang, Kai Wang. Validation & application of next-generation sequencing panel YuanSu S for gene rearrangements/fusions detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2283.

Abstract 1191: Differences in gene mutation characteristics of gastric, intestinal and colorectal stromal tumors

Abstract Background: Gastrointestinal stromal tumors (GIST), which were thought to originate from interstitial cells of Cajal,is the most common malignant mesenchymal neoplasm, and account for 1%-3% of digestive tract tumors. Drug development in GIST has successfully utilized the KIT/PDGFRA oncogenic mutation. At the same time, drug sensitivity and resistance, such as imatinib resistance, is a problem should be paid more attention. We analyzed features of kit/pdgfra mutation in different region GIST of Chinese patients, which will provide reference information for the use of targeted drugs among patients with gastric, intestinal or colorectal stromal tumors. Methods: Tumor samples of 201 HCC patients were consecutively collected in China from January 2018 to June 2020, next generation sequencing (NGS) was performed to detect gene mutation by 3D Medicines, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA. Results: All these tissue samples were divided as stomach (n=109), small intestine (n=79), colon and the rectum (n=13). The average age of three group were 57, 55 and 50, the proportion of males in gastric, intestinal and colorectal stromal tumor were 64.2% (79/109), 60.8% (48/79) and 61.5%(8/13), respectively. NGS analysis showed that, frequency of kit were 71.5% (78/109), 83.5% (66/79) and 61.5% (8/13), among witch, mutation of exon 9 were 1.8%(2/109), 27.8% (22/79), 30.7% (4/13), and exon 11 were 66.1%(72/109), 53.2%(42/79), 30.8%(4/13); frequency of pdgfra were 14.7%(16/109), 3.8%(3/79) and 7.7%(1/13), and mutation frequency of pdgfra exon 18 were 11.9% (13/109), 1.3%(1/79), 7.7%(1/13). Conclusions: GIST is more inclined to occur in male. kit was the main mutation in GIST, however, only 1.8% of gastric GIST carry exon 9 mutations, a large proportion (66.1% and 53.2%) of gastric and intestinal GISTs carry exon 11 mutations. Besides, more mutation of pdgfra happened in gastric GIST than intestinal and colorectal GISTs. These results demonstrate that GIST occurred in different location may show different sensitivity or resistance to drugs targeting KIT/PDGFRA signals. Citation Format: Qian Wang, Hushan Zhang, Sihui Zhao, Jianxun Wang, Ning Ma, Jun Zhu. Differences in gene mutation characteristics of gastric, intestinal and colorectal stromal tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1191.