Test Name: MLH1


Methodology: IHC


Test Description

MLH1 is a DNA mismatch repair protein. Loss of MLH1 expression in carcinoma or adenoma cells, as a result of mutation in MLH1 or PMS2 genes, is associated with hereditary non-polyposis cancer syndrome (Lynch syndrome, Muir-Torre syndrome). MLH1 and PMS2 expression may also be altered as a result of MLH1 promoter hypermethylation, a sporadic abnormality associated with BRAF V600E mutation. Evaluation of MLH1 expression by immunohistochemistry in colorectal and endometrial adenocarcinomas, as well as in sebaceous neoplasms is of value in identifying patients with Lynch syndrome. This information is important in management of their neoplasms, as well as for lifelong monitoring and genetic counseling. This test may be performed on tumor samples individually, or as a part of the MMR panel .


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.


Storage and Transport

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


Specimen Rejection Criteria

Click here to reference the specimen rejection criteria.


Turn Around Time (TAT): 2-3 Days


CPT Codes*: 88341, 88342, 88360


*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.