MSH2 Microsatellite Instability

Casandra

Casandra Test Code MP23622Version 1 (DRAFT)

Performing Lab

Lab MPLNLab Test ID I MSH2CPT Code 88342

MSH2 Microsatellite Instability

Companion Diagnostic

MSH2 Microsatellite Instability is an FDA-approved companion diagnostic used to help identify patients who may be eligible for targeted therapies.

View CDx Profile

Clinical Use

Order Test

Use

MutS Homologue 2 (MSH2) is a mismatch repair (MMR) protein and its deficiencies result in microsatellite instability (MSI) in cancers such as colorectal and endometrial. This test is significant for evaluating the presence of microsatellite instability which is associated with malignancies and can guide therapeutic decisions, especially in relation to the FDA-approved companion diagnostic for venting MMR RxDx use.

Special Instructions

Special considerations for specimen handling include that fresh tissues may be fixed in formalin for 24-72 hours by collection sites and then transferred to 70% ethanol for longer term storage if necessary. Positively charged glass slides are mandated to prevent background staining and loss of tissue.

Limitations

Specimens must be fixed in 10% neutral buffered formalin (NBF) or B plus; all other fixatives will be rejected. Unstained slides must be left unbaked and on positively charged glass slides. The test uses immunohistochemistry methodology, limiting it to protein expression evaluation, not suitable for genetic mutation analysis. The fresh tissue stability limits are a maximum of 72 hours, so prolonged delays in testing can affect results.

Test Details

FDA Approved

Companion Diagnostic

Methodology

Immunoassay (IHC)

Biomarkers

This component utilizes immunohistochemistry to detect the presence and expression levels of the MSH2 protein, which is crucial for identifying microsatellite instability often found in certain cancer types.

MSH2

Protein

IHC • Expression • Categorical (e.g., Positive / Negative / Indeterminate)

Result Turnaround Time

2 days

Specimen

Tissue (Fixed (Non-FFPE))

Volume

Not provided

Minimum Volume

Not provided

Collection Instructions

Fixative should be at a 20:1 fixative to tissue ratio, 10% neutral buffered formalin for 6-72 hours (48-72 hours PREFERRED). Specimens may be transferred to 70% alcohol for transport after fixation.