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

Sep 24, 2026

Different cancers carry multiple genetic mutations that may vary across tumour sites. Small tissue biopsies can miss part of the genomic landscape. Liquid biopsy can increase the likelihood of detecting mutations across disease stages and during progression when tissue sampling is limited. 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).

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages7

Reading Time18 min

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Introduction

Liquid biopsy and ctDNA in cancer diagnosis and monitoring

Plasma ctDNA molecular profiling

Clinical guidance and testing limitations

Tumour site, blood-brain barrier, and ctDNA levels

Brain metastases and metastatic spread

medicina Case Report 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 Veronica Aran 1, *, Vinicius Mansur Zogbi 2, Renan Lyra Miranda 3, Felipe Andreiuolo 3, Nathalie Henriques Silva Canedo 3, Carolina Victor Nazar² 2, Paulo Niemeyer Filho 2 and Vivaldo Moura Neto 1 Citation: 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 Academic Editor: Seung-Gu Yeo Received: 22 November 2022 Revised: 17 February 2023 Accepted: 22 February 2023 Published: 25 February 2023 Copyright: © 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/)) . 1 Laboratârio de Biomedicina do C²rebro, Instituto Estadual do C²rebro Paulo Niemeyer, Rua do Rezende156-Centro, Rio de Janeiro 20231-092, Brazil 2 Neurosurgery Division, Instituto Estadual do C²rebro Paulo Niemeyer, Rua do Rezende156-Centro, Rio de Janeiro 20231-092, Brazil 3 Neuropathology and Molecular Genetics Laboratory, Instituto Estadual Do C²rebro Paulo Niemeyer, Rua do Rezende156-Centro, Rio de Janeiro 20231-092, Brazil * [Correspondence: varanponte@gmail.com](Correspondence: varanponte@gmail.com); Tel.: +55-2-19-7208-8811 Abstract: 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. Keywords: brain metastases; lung hepatoid adenocarcinoma; K-RAS; liquid biopsy; ddPCR 1. Introduction The 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] . Plasma 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

FAQs

Why can liquid biopsy improve mutation detection compared with tissue biopsy?

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.

What biomarkers and mutation were reported in this case study?

The case report describes K-RAS mutations present in both the brain tumour tissue and circulating tumour DNA (ctDNA) detected in the bloodstream.

How does ctDNA relate to prognosis and treatment decisions in cancer?

ctDNA analysis supports prognosis, identification of gene alterations, selection of targeted therapies, and disease monitoring, particularly when tissue testing is not feasible.

Sep 24, 2026

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