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Order Code IHC Mismatch Repair (MMR) Protein Immunohistochemistry Only, Tumor

Useful For

Evaluation of tumor tissue to identify patients at risk for having hereditary nonpolyposis colon cancer/Lynch syndrome

Additional Tests

Test ID Reporting Name Available Separately Always Performed
MSH2I MSH-2, Immunostain No, (bill only) Yes
MSH6I MSH-6, Immunostain No, (bill only) Yes
PMS2I PMS-2, Immunostain No, (bill only) Yes
MLH1I MLH-1, Immunostain No, (bill only) Yes

Testing Algorithm

When this test is ordered, MLH1, MSH2, MSH6, and PMS2 stains will always be performed at an additional charge.


See Lynch Syndrome Testing Algorithm in Special Instructions.

Method Name

Immunohistochemical Staining

Reporting Name

MMR Protein, IHC Only, Tumor

Specimen Type


Specimen Required

Tumor tissue is required.


Specimen Type: Tissue block and slide

Collection Instructions:

1. Submit formalin-fixed, paraffin-embedded tissue block (preferred) or 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides (5-micron thick sections) of the tumor tissue.

2. Sections should contain tumor tissue.

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Ambient (preferred)

Reject Due To

Hemolysis NA
Lipemia NA
Icterus NA
Other Specimens that have been decalcified (all methods); specimens that have not been formalin-fixed, paraffin-embedded; bone marrow in EDTA

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Monday through Friday; Varies

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

MLH-1, Immunostain

88341 (if appropriate)


MSH-2, Immunostain

88341 (if appropriate)


MSH-6, Immunostain

88341 (if appropriate)


PMS-2, Immunostain

88342 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
IHC MMR Protein, IHC Only, Tumor In Process


Result ID Test Result Name Result LOINC Value
53258 Result Summary 50397-9
53259 Result In Process
54443 Interpretation 59465-5
53260 Specimen 31208-2
53261 Source 31208-2
54444 Tissue ID 80398-1
53262 MLH1 IHC 81691-8
53263 MSH2 IHC 81692-6
53264 MSH6 IHC 81693-4
53265 PMS2 IHC 81694-2
53266 Released By 18771-6


1. Molecular Genetics: Inherited Cancer Syndromes Patient Information (T519) in Special Instructions

2. If not ordering electronically, complete, print, and send an Oncology Test Request (T729) with the specimen.