MLH1, a mismatch repair protein involved in maintaining the integrity of genetic information, alongside MSH2, MSH6 and PMS2. During DNA replication, strand misalignment can occur resulting in alterations to microsatellite repeats, often referred to as microsatellite instability (MSI). These defects in DNA repair pathways have been linked to human carcinogenesis. Mutations in the MLH1 gene have been reported to be found in tumors with MSI, such as some forms of colon cancer eg. Hereditary nonpolyposis colon cancer (HNPCC), a subset of sporadic carcinomas and breast cancer. Loss of expression of MLH1 has also been reported in acute lymphoblastic leukemia, endometrial carcinoma, gastric carcinoma and ovarian carcinoma.
MLH1
- Immunohistochemistry (IHC)
Specimen Requirements
Preferred specimen (FFPE block):
A formalin-fixed, paraffin-embedded (FFPE) tissue block is the preferred specimen type. Use 10% NBF fixative; do not use zinc or mercury fixatives.
If submitting slides (instead of a block):
Submit the following. All slides cut at 4–5 microns. Please use positively-charged slides and 10% NBF fixative.
H&E slide: One (1) unbaked, unstained slide for H&E staining (required)
Cut Slides: Two (2) positively charged unstained slides for each IHC test/antibody ordered
Specimen identification:
Block and slide identifiers should be clearly written and match exactly with the specimen ID and specimen labeling as noted on the requisition.
A formalin-fixed, paraffin-embedded (FFPE) tissue block is the preferred specimen type. Use 10% NBF fixative; do not use zinc or mercury fixatives.
If submitting slides (instead of a block):
Submit the following. All slides cut at 4–5 microns. Please use positively-charged slides and 10% NBF fixative.
H&E slide: One (1) unbaked, unstained slide for H&E staining (required)
Cut Slides: Two (2) positively charged unstained slides for each IHC test/antibody ordered
Specimen identification:
Block and slide identifiers should be clearly written and match exactly with the specimen ID and specimen labeling as noted on the requisition.
Storage and Transportation
Slides may be stored at room temperature; transport with cold pack, making sure cold pack is not in direct contact with specimen.
NYS Clients: Please provide Date and Time of Collection.
CPT Code(s)*
88342 x 1 or 88341 x 1; 88360 x 1; 88361 x 1
Turnaround time
1-2 Days
Image Analysis for Global: 2 Days
Image Analysis for (Tech-Only): 2 Days
Tech-Only (stain only): 24 Hours
Level of Service
- Global
- Tech Only
Integrations
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New York Approved: Yes
*The CPT codes provided with our test descriptions are based on AMA guidelines and are for informational purposes only. Correct CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.
Biomarkers
Immunohistochemistry (IHC)
| Expression | |||||
|---|---|---|---|---|---|
| MLH1 | |||||
Last Updated: March 19, 2026