CPT 81292 MLH1 Full Gene Sequencing Reimbursement

CPT code 81292 designates full-gene sequencing of the MLH1 gene, a key mismatch repair gene implicated in Lynch syndrome and hereditary colorectal cancer risk. Nationally, comprehensive MLH1 sequencing supports diagnostic confirmation, risk stratification, and cascade testing in affected families, making it a clinically significant molecular diagnostic service. Payers commonly covering this service include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.

Readers will learn what CPT code 81292 represents, where the test is typically performed, and the clinical context for ordering full MLH1 sequencing. The publication summarizes payer coverage considerations, common modifiers associated with laboratory services, and the service line and site of service typically involved. It also outlines what benchmarks and policy topics to review for labs and payers, including coding specificity, clinical indications for comprehensive sequencing, and integration with hereditary cancer evaluation pathways. Data not available in the input is noted where applicable.

Billing Code Overview

CPT code 81292 describes analysis of the full gene sequence of the mutL homolog 1 (MLH1) gene, also known as the colon cancer or nonpolyposis type 2 gene. The service involves laboratory technical work to sequence and detect variants across the entire coding region of MLH1 for clinical genetic evaluation.

Service type: Molecular diagnostic laboratory testing — full gene sequencing

Typical site of service: Clinical diagnostic laboratory / reference laboratory

Clinical Context

A 48-year-old patient with a personal history of colorectal adenocarcinoma and a family history of early-onset colon cancer is referred for germline genetic testing to evaluate for Lynch syndrome. The ordering clinician — typically a gastroenterologist, oncologist, or genetic counselor — requests full sequencing of the MLH1 gene to detect pathogenic or likely pathogenic variants that predispose to mismatch repair deficiency. The clinical workflow begins with pre-test counseling and informed consent, specimen collection (peripheral blood or saliva), shipment to a molecular diagnostics laboratory, DNA extraction, and next-generation sequencing or Sanger sequencing of the entire MLH1 coding region and relevant intron–exon boundaries. The laboratory analyst performs the technical testing represented by 81292, interprets sequence variants according to ACMG/AMP guidelines, and issues a technical and interpretive report. Results are routed to the ordering provider; post-test genetic counseling is typically recommended to discuss pathogenic findings, cascade testing for at-risk relatives, and implications for surveillance and management.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when only the laboratory interpretation/reporting (professional component) is billed separately from the technical processing by a separate entity.

Taxonomy Code	Specialty	Notes
`207Q00000X`	Clinical Molecular Genetics Laboratory	Laboratories performing molecular sequencing and variant interpretation.
`207RG0100X`	Clinical Laboratory Geneticist	Specialists who oversee molecular diagnostic testing and quality.
`208D00000X`	Medical Genetics & Genomics	Physicians who order and interpret germline testing for hereditary cancer syndromes.
`207L00000X`	Pathology-Laboratory Medicine	Pathologists who direct molecular labs and sign out diagnostic reports.
`363LF0000X`	Genetic Counselor	Professionals who provide pre- and post-test counseling and coordinate testing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`Z15.09`	Genetic susceptibility to other malignant neoplasms	Used when a patient has a known family history or suspicion of hereditary cancer risk prompting MLH1 testing.
`C18.9`	Malignant neoplasm of colon, unspecified	Indicates a personal history of colon cancer and is a common indication to evaluate for Lynch syndrome via `81292`.
`Z80.0`	Family history of malignant neoplasm of digestive organs	Family history of colorectal cancer supports MLH1 germline analysis.
`D01.0`	Carcinoma in situ of colon	Early neoplastic findings may prompt germline testing for mismatch repair gene variants.
`Z85.048`	Personal history of other malignant neoplasm of large intestine	A history of colorectal cancer that warrants consideration of germline MLH1 sequencing.
`R19.5`	Other fecal abnormalities	Clinical findings such as occult blood prompting colonoscopy and cancer diagnosis which can lead to genetic testing.
`Z83.71`	Family history of colonic polyposis	Relevant when a strong family history of polyps/colorectal cancer triggers MLH1 testing.
`K63.5`	Polyp of colon	Presence of multiple or early-onset polyps may be associated with hereditary syndromes evaluated by MLH1 sequencing.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81162`	BRCA1 and BRCA2 full gene sequence analysis	Performed in patients with hereditary breast/ovarian cancer suspicion; often ordered in parallel or as part of a hereditary cancer panel alongside `81292` when broader risk assessment is needed.
`81291`	Analysis of the entire gene sequence for mutL homolog 2 (MSH2)	MSH2 sequencing is commonly ordered together with MLH1 sequencing for comprehensive Lynch syndrome evaluation.
`81293`	Analysis of the entire gene sequence for mutS homolog 6 (MSH6)	MSH6 sequencing is frequently performed with MLH1 to assess mismatch repair gene mutations.
`81445`	Targeted genomic sequence analysis panel (multiple genes)	Used when a multi-gene hereditary cancer panel including `MLH1` is ordered; `81292` may be reported individually or as part of the panel depending on billing methodology.
`88360`	Immunohistochemistry staining for DNA mismatch repair proteins	Performed on tumor tissue to screen for loss of MLH1 protein expression prior to germline sequencing with `81292`.

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Summary & Overview

CPT 81292: MLH1 Full Gene Sequencing