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Review Article
Year: 2022 I Volume: 4 I Issue: 1I Pages I 1-6 

Microsatellite Instability Testing Approaches in Clinical Practice: A comparative Review

Nagwa Ibrahim 1, Hoda Mokhtar 2, Ashraf Farrag 2,3

1Global Healthcare Activities SRL, Cluj-Napoca, Romania

2Prince Sultan Military Medical City, Department of Adult Oncology, Riyadh, Saudi Arabia

3 Clinical Oncology Department, Assiut university Hospitals, Assiut, Egypt.

* Corresponding Author:

Nagwa Ibrahim, Pharm D, PhD

Email address: 

Source of funding:  None


Conflict of interest: None

Submission date: 20 February 2022

Acceptance date: 18 March 2022

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Key wards: Microsatellite Instability (MSI) testing approaches, clinical practice, Immunohistochemistry (IHC), Next-Generation Sequencing (NGS), Polymerase chain reaction (PCR), liquid biopsy, comparative review


Immunotherapy development particularly with PD-1 inhibitors, has changed the treatment paradigm for certain types of cancer. The group of malignancies that are characterized by deficiency in the mismatch repair (dMMR) / microsatellite instability high (MSI-H) is an example and are highly sensitive to PD-1 blockade. MSI testing and analysis of MMR expression play an important role in the detection of patient's eligibility to immunotherapy, prognosis and chemotherapy sensitivity. There are two approaches for detection of MSI status. The first is tissue biopsy which is up to date still considered as the gold standard for MSI assessment. This technique face challenges due to their invasiveness, prolonged turnaround time for test results and adversity in potential sampling due to tissue heterogeneity. It involves the testing of adequate tissue with a high concentration of cancer cells and require paired normal tissues. Application of this methodology might be hindered when surgery is not an option or when the tissue is insufficient.  The second approach is liquid biopsy that diagnose MSI in blood samples (bMSI). It is non-invasive, simple, fast technique that based on the analysis of circulating tumor DNA which is a fraction of cfDNA, circulating tumor cell (CTCs), and other tumor derived material in blood plasma. One of the primary technological hurdles for bMSI determination is that it necessitates highly sensitive procedures as low as 0.01 percent in early stages of cancers. In case of tissue-based procedure the assays used for MSI testing are immunohistochemistry (IHC) and polymerase chain reaction (PCR), while in case of liquid biopsy the next generation sequencing (NGS) tool is used. Our aim is to comparatively review and summarize the published research about MSI testing approaches to provide a guidance easily utilized in oncology clinical practice. 

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