888 443 3311

MMR Panel by IHC (MLH1, MSH2, MSH6, PMS2)
Clinical Significance
A well-defined subtype of colorectal cancer (CRC) is characterized by a deficiency in the mismatch repair (MMR) pathway. MMR deficiency not only contributes to the pathogenesis of a large proportion of CRC, but also determines the response to many of the drugs that are frequently used to treat this disease. Immunohistochemistry (IHC) for the human homologues of the E. coli mismatch repair genes MutL (MLH) and MutS (MSH) and post-meiotic segregation (PMS). MLH1, MSH2, MSH6, and PMS2 protein expression and microsatellite instability (MSI) are well-established tools to screen for Lynch syndrome (LS).

Specimen Requirements
  • A formalin-fixed, paraffin-embedded (FFPE) tissue block is preferred specimen type
  • or
  • One (1) unbaked, unstained slide cut at 4-5 microns for H&E staining (required) and two to three (2-3) positively charged unstained slides cut at 3-4 microns for each test/antibody ordered
  • Use cold pack during transport of paraffin blocks and unstained slides. Cold pack should not be placed in direct contact with the specimen during shipping
  • Fresh tissue biopsy, peripheral blood, bone marrow [core/clot/aspirate], malignant fluids and FNA specimens should be transported in container with 10% Neutral Buffered Formalin
CPT Code(s)*
88342 x 1, 88341 x 3 or 88360 x 4 or 88361 x 4

Level of Service
Image Analysis
Stain Only

Turnaround Time
12 - 48 hours
24 - 36 hours (Technical) and 48 hours (Global)

*These CPT codes are general codes frequently used for these tests. The correct CPT code should be selected on a case-by-case basis by a qualified coder.
†Please note the information provided is intended as a guideline. Turnaround time is measured from the time of receipt of the specimen at our laboratory to the time the test result is made available to the client. As with all healthcare matters, the facts of a particular case may necessitate a turnaround time that is longer than stated above, the times mentioned above are our laboratory times for most, standard cases.