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This case report describes a patient with brain metastasis and lung cancer showing K-RAS mutations in both brain tumour tissue and circulating tumour DNA (ctDNA).",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/healthcare/","Healthcare",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/the-use-of-liquid-biopsy-in-the-molecular-analysis-of-plasma-compared-to-the-tumour-tissue-from-a-patient-with-brain-metastasis-a-case-report/383437/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/the-use-of-liquid-biopsy-in-the-molecular-analysis-of-plasma-compared-to-the-tumour-tissue-from-a-patient-with-brain-metastasis-a-case-report/383437.png","ImageObject",300,407,{"name":42,"@type":43},"Olivia Brown","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-10-29","2026-09-24",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",13,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"Why can liquid biopsy improve mutation detection compared with tissue biopsy?","Question",{"text":63,"@type":64},"Small tissue biopsies may not represent the full genetic landscape of a tumour. Liquid biopsy can provide broader access to tumour-derived mutations across different disease stages.","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"What biomarkers and mutation were reported in this case study?",{"text":68,"@type":64},"The case report describes K-RAS mutations present in both the brain tumour tissue and circulating tumour DNA (ctDNA) detected in the bloodstream.",{"name":70,"@type":61,"acceptedAnswer":71},"How does ctDNA relate to prognosis and treatment decisions in cancer?",{"text":72,"@type":64},"ctDNA analysis supports prognosis, identification of gene alterations, selection of targeted therapies, and disease monitoring, particularly when tissue testing is not feasible.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},383437,1790405607,{"code":4,"msg":82,"data":83},"success",[84,88,92,96,101,106,110,115,120,123,127],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":89,"show_sort_weight":90,"slug":91},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":93,"show_sort_weight":94,"slug":95},"Exam",70,"exam",{"id":97,"doc_module":4,"doc_module_name":25,"category_name":98,"show_sort_weight":99,"slug":100},5,"Comic",60,"comic",{"id":102,"doc_module":4,"doc_module_name":25,"category_name":103,"show_sort_weight":104,"slug":105},6,"Technology",50,"technology",{"id":107,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":108,"slug":109},7,40,"healthcare",{"id":111,"doc_module":4,"doc_module_name":25,"category_name":112,"show_sort_weight":113,"slug":114},8,"Research & Report",30,"research-report",{"id":116,"doc_module":4,"doc_module_name":25,"category_name":117,"show_sort_weight":118,"slug":119},9,"Religion & Spirituality",20,"religion-spirituality",{"id":118,"doc_module":4,"doc_module_name":25,"category_name":121,"show_sort_weight":118,"slug":122},"World Cup","world-cup",{"id":124,"doc_module":4,"doc_module_name":25,"category_name":125,"show_sort_weight":124,"slug":126},10,"Lifestyle","lifestyle",{"id":128,"doc_module":4,"doc_module_name":25,"category_name":129,"show_sort_weight":97,"slug":130},19,"General","general",{"code":4,"msg":82,"data":132},{"doc_id":79,"user_id":133,"nickname":42,"user_avatar":134,"doc_module":4,"category_id":107,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":135,"file_id":136,"file_url":137,"file_type":138,"file_size":139,"view_count":55,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":107,"language":140,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":12,"update_tm":144,"read_time":145},16904993612988,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","medicina  \nCase Report  \nThe Use of Liquid Biopsy in the Molecular Analysis of Plasma Compared to the Tumour Tissue from a Patient with Brain Metastasis: A Case Report  \nVeronica Aran 1, *, Vinicius Mansur Zogbi 2, Renan Lyra Miranda 3, Felipe Andreiuolo 3,  \nNathalie Henriques Silva Canedo 3, Carolina Victor Nazar² 2, Paulo Niemeyer Filho 2 and Vivaldo Moura Neto 1  \nCitation: Aran, V.; Zogbi, V.M.; Miranda, R.L.; Andreiuolo, F.; Silva Canedo, N.H.; Nazaré, C.V.; Niemeyer Filho, P.; Neto, V.M. The Use of Liquid Biopsy in the Molecular Analysis of Plasma Compared to the Tumour Tissue from a Patient with Brain Metastasis: A Case Report. Medicina 2023, 59, 459 . [https://doi.org/10.3390/](https://doi.org/10.3390/)[ ](https://doi.org/10.3390/)medicina59030459  \nAcademic Editor: Seung-Gu Yeo  \nReceived: 22 November 2022  \nRevised: 17 February 2023  \nAccepted: 22 February 2023  \nPublished: 25 February 2023  \nCopyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([https://](https://)[ ](https://)[creativecommons.org/licenses/by/](creativecommons.org/licenses/by/)[ ](creativecommons.org/licenses/by/)[4.0/](4.0/)) .  \n1 Laboratârio de Biomedicina do C²rebro, Instituto Estadual do C²rebro Paulo Niemeyer, Rua do Rezende156-Centro, Rio de Janeiro 20231-092, Brazil  \n2 Neurosurgery Division, Instituto Estadual do C²rebro Paulo Niemeyer, Rua do Rezende156-Centro, Rio de Janeiro 20231-092, Brazil  \n3 Neuropathology and Molecular Genetics Laboratory, Instituto Estadual Do C²rebro Paulo Niemeyer, Rua do Rezende156-Centro, Rio de Janeiro 20231-092, Brazil  \n* [Correspondence: varanponte@gmail.com](Correspondence: varanponte@gmail.com); Tel.: +55-2-19-7208-8811  \nAbstract: Different cancers have multiple genetic mutations, which vary depending on the affected tumour tissue. Small biopsies may not always represent all the genetic landscape of the tumour. To improve the chances of identifying mutations at different disease stages (early, during the disease course, and refractory stage), liquid biopsies offer an advantage to traditional tissue biopsy. In addition, it is possible to detect mutations related to metastatic events depending on the cancer types analysed as will be discussed in this case report, which describes a patient with brain metastasis and lung cancer that harboured K-RAS mutations both in the brain tumour and in the ctDNA present in the bloodstream.  \nKeywords: brain metastases; lung hepatoid adenocarcinoma; K-RAS; liquid biopsy; ddPCR  \n1. Introduction  \nThe minimally invasive technique known as liquid biopsy can detect tumour-derived biomarkers in body fluids such as in blood. Circulating tumour DNA (ctDNA) refers to DNA of tumour origin, and being cell-free [1] . In fact, there are two sources of DNA that can be noninvasively assessed in blood circulation: cell-free circulating DNA (cfDNA) and the tumour-derived DNA fraction (ctDNA) . They consist of small fragments of nucleic acid that are not associated with cells or cell fragments, and several studies have shown that ctDNA is present in advanced neoplasia [2] . This probably occurs because of apoptosis, cell necrosis, and active tumour secretion since tumour cell division occurs faster than normal cell division [3] . Thus, analysis of ctDNA is considered helpful in the prognosis, identification of alterations in different genes, selection of targeted therapies, and disease monitoring in cancer [4] . In addition, apart from blood (serum or plasma), sources of cfDNA/ctDNA include urine, saliva, cerebrospinal fluid, seminal fluid, and pleural fluid samples [3,5] .  \nPlasma offers the possibility to give crucial molecular information via the analysis of ctDNA to detect cancer-related mutations in distinct tumour types, such as already described in the profiling of lung, colorectal, brain, and breast tumours, showing a promising perspect","cbCaito2IWoz5KPJ","https://ap.wps.com/l/cbCaito2IWoz5KPJ","pdf",4886279,"English","# Introduction\n## Liquid biopsy and ctDNA in cancer diagnosis and monitoring\n## Plasma ctDNA molecular profiling\n## Clinical guidance and testing limitations\n## Tumour site, blood-brain barrier, and ctDNA levels\n## Brain metastases and metastatic spread","[{\"question\":\"Why can liquid biopsy improve mutation detection compared with tissue biopsy?\",\"answer\":\"Small tissue biopsies may not represent the full genetic landscape of a tumour. Liquid biopsy can provide broader access to tumour-derived mutations across different disease stages.\"},{\"question\":\"What biomarkers and mutation were reported in this case study?\",\"answer\":\"The case report describes K-RAS mutations present in both the brain tumour tissue and circulating tumour DNA (ctDNA) detected in the bloodstream.\"},{\"question\":\"How does ctDNA relate to prognosis and treatment decisions in cancer?\",\"answer\":\"ctDNA analysis supports prognosis, identification of gene alterations, selection of targeted therapies, and disease monitoring, particularly when tissue testing is not feasible.\"}]","The Use of Liquid Biopsy in the Molecular Analysis of Plasma Compared to the Tumour Tissue from a Patient with Brain Metastasis - A Case Report | PDF",1790257032,18]