MLH1 by IHC

Alphabetical Test listing

MLH1 by IHC-12376 - Technical only, 12379 - Technical & interpretation

Test name:

MLH1 by IHC

Test number:

12376 - Technical only, 12379 - Technical & interpretation

Excellian order number:

LAB12376
LAB12379

Alternate names:

Microsatellite instability marker

Tests included:

All IHC stains will include a positive control tissue

Useful for:

Used in a panel to identify patients at high risk for having hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome
IHC analysis is helpful for identifying the gene(s) responsible for the defective DNA mismatch repair within the tumor; the majority of MSI-H tumors show a loss of expression of at least 1 of the 4 mismatch repair genes
MSI-H phenotype or loss of protein expression by IHC within a tumor does not distinguish between somatic and germline mutations. Genetic testing of the gene indicated by IHC analysis can help to distinguish between these 2 possibilities

Specimen type:

Tissue

Processing instructions:

Submit a formalin-fixed, paraffin-embedded (FFPE) tissue block

Transport container:

FFPE tissue block

Alternate transport container:

FFPE tissue section mounted on a charged, unstained slide

Transport and stability:

Ambient (preferred)

Reason for rejection:

Unlabeled/mislabeled block
Insufficient tissue
Slides broken beyond repair

Performing lab:

AHL - Immunohistochemistry

Days set up:

Mo - Fr

TAT:

1 - 2 days

Method:

Immunohistochemical staining and microscopic examination

Reference ranges:

If requested, an interpretive report will be provided

Clinical information:

Specifications

Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is an autosomal dominant hereditary cancer syndrome associated with germline mutations in the mismatch repair genes: MLH1, MSH2, MSH6, and PMS2
Patients with HNPCC have an increased risk of developing colorectal and endometrial cancer

Staining pattern

Nuclear staining of internal control lymphocytes, and MLH1 intact tumor cells
Absence of staining for MLH1 in tumor nuclei indicates loss of protein expression for this marker

References

Burgart LJ: Testing for defective DNA mismatch repair in colorectal carcinoma. A practical guide. Arch Pathol Lab Med 2005;129:1385-1389.

CPT codes:

88342 - 1st stain
88341 - each additional stain

Date created:

10/30/2017

Revised date:

10/19/2018

Review date:

01/12/2024