Hereditary Nonpolyposis Colorectal Cancer (HNPCC): MLH1 (Known Mutation)

CPT: Contact CPT coding department at 800-222-7566, ext 6-8400.
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Test Details

Use

Identify who in a family harbors the familial mutation and is at high risk of the disease and who does not harbor the familial mutation and is not at increased risk of the disease. Family testing for known familial mutations can identify presymptomatic mutation carriers within affected families who are at high risk of developing the familial disease.

Limitations

Selected regions of the coding sequence of MLH1 are amplified by polymerase chain reaction and each PCR product (amplicon) then sequenced bi-directionally, using Sanger sequencing. Nucleotide and codon number are based on the mRNA isoform NM_000249 for the MLH1 gene.

Sequencing cannot detect variants in regions not covered by this analysis, including noncoding or deep intronic variants and may not reliably detect changes in repetitive elements, such as microsatellite repeats. Sequencing may not detect mosaic variants, inversions, or other genomic rearrangements such as transposable element insertions. Sequence analysis may also be affected by allele drop-out due to the presence of a rare variant under a primer site or homopolymeric regions. The method does not allow any conclusion as to whether two heterozygous variants are present on the same or on different chromosome copies.

This test is not intended to detect somatic variants. Bone marrow transplantation may affect the outcome of these results. Please contact LabCorp to discuss testing options at 1-800-345-GENE.

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the US Food and Drug Administration (FDA).

Methodology

DNA sequencing

Additional Information

Once a mutation is identified in an index patient, family members can be tested for the presence of that specific mutation (single-amplicon testing). Please note, if additional amplicons are required for family testing, the patient will be charged for each additional amplicon.

Specimen Requirements

Specimen

Whole blood; DNA is accepted (Call 800-345-4363 for DNA collection information.)

Volume

2 mL

Container

Lavender-top (EDTA) tube

Collection

Samples may be stored for brief periods at 4°C. Ship overnight at room temperature.

Storage Instructions

Maintain specimen at room temperature.

Causes for Rejection

Container broken or leaking; container not labeled or label not legible; improper anticoagulant

Clinical Information

Special Instructions

This option is available when the mutation is known and can be documented by the ordering physician. If the mutation cannot be documented, please order test 511615.

Test orders must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form: Consent for Genetic Testing. In the case of family tests (ie, known mutations), please submit the result report of the first patient tested in the family (the index case), if not performed at a LabCorp facility. Other family members are subsequently tested for the specific mutation found in the first patient tested.

References

Evans JT, Vana J, Aronoff BL, Baker HW, Murphy GP. Management and survival of carcinoma of the colon: Results of a national survey of the American College of Surgeons. Ann Surg. 1978 Dec;188(6):716-720.736649
Hutter P, Wijnen J, Rey-Berthod C, et al. An MLH1 haplotype is over-represented on chromosomes carrying an HNPCC predisposing mutation in MLH1.J Med Genet. 2002 May;39(5):323-327.12011148
Kohlmann W, Gruber SB. Lynch syndrome. In: Pagon RA, Adam MP, Ardinger HH, et al, eds. GeneReviews®. 2004 Feb 5; Seattle, Wash: University of Washington;1993-2014. Available at: http://www.ncbi.nlm.nih.gov/books/NBK1211/.20301390
Online Mendelian Inheritance in Man (OMIM™). Colorectal cancer, hereditary nonpolyposis, type 8; HNPCC8. Baltimore, Md: Johns Hopkins University. Available at: http://www.ncbi.nlm.nih.gov/omim/613244.
Online Mendelian Inheritance in Man (OMIM™). Lynch syndrome I. Baltimore, Md: Johns Hopkins University. Available at: http://www.ncbi.nlm.nih.gov/omim/120435.
Online Mendelian Inheritance in Man (OMIM™). MutL, E coli, homolog of, 1; MLH1. Baltimore, Md: Johns Hopkins University. Available at:http://www.ncbi.nlm.nih.gov/omim/120436.
Online Mendelian Inheritance in Man (OMIM™). MutS, E coli, homolog of, 2; MSH2. Baltimore, Md: Johns Hopkins University. Available at:http://www.ncbi.nlm.nih.gov/omim/609309.
Online Mendelian Inheritance in Man (OMIM™). Postmeiotic segregation increased, S cerevisiae, 2; PMS2. Baltimore, Md: Johns Hopkins University. Available at: http://www.ncbi.nlm.nih.gov/omim/600259.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
511635 HNPCC: MLH1 Family 511748 Test Order Review N/A
511635 HNPCC: MLH1 Family 511749 Tracking N/A
Reflex Table for Test Order Review
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 511751 MLH1 Family 511752 Specimen Type 31208-2
Reflex Table for Test Order Review
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 511751 MLH1 Family 511753 Result 41086-0
Reflex Table for Test Order Review
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 511751 MLH1 Family 511754 Director Review 72486-4
Reflex Table for Test Order Review
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 511751 MLH1 Family 512123 PDF 80563-0

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The LOINC® codes are copyright © 1994-2018, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf