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CPT 81521: mRNA Microarray Breast Cancer Recurrence Score

CPT code 81521 denotes an mRNA microarray–based molecular diagnostic assay that analyzes 70 genes and applies an algorithm to produce a breast cancer recurrence score. This test informs prognostic assessment and can influence systemic therapy decisions, making it clinically significant across oncology care and laboratory services nationwide. Payers commonly covering or evaluating coverage for this service include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.

Readers will learn what the code represents, the clinical context for use, and the national payer landscape relevant to reimbursement and coding practice. The publication provides benchmarks and comparative coverage context, summarizes policy updates affecting molecular diagnostics, and outlines coding and billing considerations for laboratories and clinicians. It also highlights typical sites of service and where the procedure fits within oncology care pathways. Data not available in the input is noted where applicable.

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Billing Code Overview

CPT code 81521 describes a laboratory service that performs mRNA microarray analysis of 70 genes and applies an algorithmic analysis combining the laboratory results with patient data to generate a breast cancer recurrence score. This is a molecular diagnostic test used to help characterize tumor biology and estimate risk of recurrence.

Service type: Molecular diagnostic laboratory testing with algorithmic clinical reporting
Typical site of service: Clinical diagnostic laboratory or reference laboratory performing high-complexity molecular testing

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CPT 81521: mRNA Microarray Breast Cancer Recurrence Score

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Get alerted when payer policies referencing 81521 are released or updated.

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Billing Code Overview

Service type: Molecular diagnostic laboratory testing with algorithmic clinical reporting
Typical site of service: Clinical diagnostic laboratory or reference laboratory performing high-complexity molecular testing

Clinical & Coding Specifications

Clinical Context

A 55-year-old woman with newly diagnosed, estrogen receptor–positive, node-negative invasive breast carcinoma undergoes primary surgical resection. The surgical pathology report documents a 1.8 cm invasive ductal carcinoma, grade 2, with clear margins and no nodal involvement on sentinel lymph node biopsy. The oncology team orders a tumor gene expression assay to determine a breast cancer recurrence score to inform adjuvant chemotherapy decisions. A fresh surgical specimen or formalin-fixed paraffin-embedded (FFPE) tissue block is sent to a certified molecular pathology laboratory. The laboratory technologist performs 81521 testing: mRNA microarray analysis of a 70-gene panel and algorithmic integration of the gene expression results with clinical variables to generate a recurrence score. The lab issues a report to the ordering medical oncologist and documents specimen accessioning, assay controls, analytic validity, and the computed recurrence score in the permanent record. Typical sites of service include an independent molecular diagnostic laboratory, hospital-based pathology lab, or a reference commercial laboratory. Typical billing uses the professional and technical component considerations depending on whether the lab performs the full test (81521 without a split) or only the technical component (TC) when applicable.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional (interpretive/analysis) component of the test separate from the technical lab work.
`TC`	Technical component	Use when billing only the laboratory instrumentation, processing, and technical portion of the service.
`90`	Reference (outside) laboratory	Use when the specimen was sent to an outside independent reference laboratory for `81521`.
`52`	Reduced services	Use when the lab performed a reduced version of the assay or partial testing due to insufficient specimen.
`53`	Discontinued procedure	Use when testing was started but discontinued prior to completion for documented technical reasons.
`59`	Distinct procedural service	Not in the original list; do not use.
`82`	Assistant surgeon not available	Use rarely; not typically applicable for lab-based `81521` but included when a procedural assistant taxonomy is billed in an unusual workflow.
`62`	Two surgeons	Not typically applicable; used only in rare surgical workflows tied to specimen procurement documentation.
`11`	Office or other outpatient visit	Use as an informational modifier rarely with lab billing in certain payer workflows; generally not used with standalone molecular test codes.
`90`	Reference (duplicate)	Duplicate of above; see earlier `90`.

Taxonomy Code	Specialty	Notes
208100000X	Anatomic Pathology	Pathologists who oversee molecular assay validation and interpretation.
208000000X	Clinical Pathology	Laboratory directors and clinical pathologists supervising molecular testing and quality control.
207L00000X	Molecular Genetic Pathology	Specialists in molecular diagnostics who develop and interpret gene expression assays.
207RP1001X	Hematology/Oncology	Medical oncologists who order the recurrence score to guide systemic therapy.
2083P0800X	Pathology and Laboratory Medicine	Laboratory directors and lab managers responsible for testing operations.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C50.911`	Malignant neoplasm of unspecified site of right female breast	Primary breast cancer diagnosis that commonly prompts `81521` recurrence score testing to guide adjuvant therapy.
`C50.912`	Malignant neoplasm of unspecified site of left female breast	As above for left-sided disease; recurrence score informs chemotherapy decisions.
`C50.611`	Malignant neoplasm of upper-outer quadrant of right female breast	Site-specific invasive breast carcinoma; tumor tissue from this lesion is used for gene expression testing.
`C50.612`	Malignant neoplasm of upper-outer quadrant of left female breast	Site-specific tumor code used for clinical documentation and to justify tumor profiling.
`D05.91`	Unspecified secondary malignant neoplasm of breast	In certain clinical contexts where recurrent or secondary breast tumor tissue is assayed to assess recurrence risk.
`Z85.3`	Personal history of malignant neoplasm of breast	May be used when evaluating risk of recurrence and considering assay utility in recurrent disease settings.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`88305`	Level IV surgical pathology, gross and microscopic examination	Performed on the breast resection specimen to provide histopathologic diagnosis and to select the tissue block sent for `81521` testing.
`88342`	Immunohistochemistry, each antibody (e.g., ER, PR, HER2)	Used to determine receptor status (ER/PR/HER2) that complements the recurrence score in treatment planning.
`87070`	Culture, bacterial; aerobic, outpatient	Data not applicable to this molecular assay workflow; included only when infection testing coincides with specimen processing.
`81210`	BRCA1 gene analysis (if clinically indicated)	May be ordered in parallel for hereditary risk assessment but is a separate genetic test from the tumor recurrence score.
`81479`	Unlisted molecular pathology procedure	Used when a novel or proprietary component of testing is performed that is not fully described by `81521`; supplemental coding in rare cases.

CPT 81490: RA Disease Activity Score from 12-Serum Biomarker Panel

CPT-81493-CORONARY-ARTERY-DISEASE-23-GENE-RT-PCR-RISK-SCORE

CPT 81493: 23-Gene RT-PCR Test with Algorithmic CAD Risk Score

CPT-81500-CA125-HE4-ALGORITHMIC-RISK-SCORE

CPT 81500: CA-125 and HE4 Laboratory Testing with Algorithmic Risk Score

CPT-81503-ALGORITHMIC-LAB-RISK-SCORE-CA125-APOLIPOPROTEIN-A1

CPT 81503: Algorithmic Laboratory Risk Score Using Multiple Biomarkers

CPT-81504-TUMOR-ORIGIN-RNA-EXPRESSION-CLASSIFIER

CPT 81504: RNA Expression Tumor Origin Classifier

CPT-81506-DIABETES-BIOMARKER-PANEL-WITH-RISK-SCORE

CPT 81506: Diabetes Biomarker Panel with Algorithmic Risk Score

CPT-81507-NIPS-CELL-FREE-DNA-TRISOMY-RISK-ANALYSIS

CPT 81507: Non-Invasive Prenatal Screening for Trisomies 13, 18, 21

CPT-81508-PAPP-A-HCG-ALGORITHMIC-RISK-ASSAY

CPT 81508: PAPP–A and hCG Laboratory Assay with Algorithmic Risk Score

CPT-81509-LAB-ALGORITHMIC-RISK-ASSESSMENT-PAPP-A-HCG-DIA

CPT 81509: Laboratory Algorithmic Risk Assessment for PAPP–A, hCG, DIA

CPT-81510-PRENATAL-TRIPLE-MARKER-ALGORITHMIC-RISK-ASSESSMENT

CPT 81510: Prenatal Triple-Analyte Algorithmic Risk Assessment

Showing 1–10 of 41

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

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Clinical & Coding Specifications

Clinical Context

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional (interpretive/analysis) component of the test separate from the technical lab work.
`TC`	Technical component	Use when billing only the laboratory instrumentation, processing, and technical portion of the service.
`90`	Reference (outside) laboratory	Use when the specimen was sent to an outside independent reference laboratory for `81521`.
`52`	Reduced services	Use when the lab performed a reduced version of the assay or partial testing due to insufficient specimen.
`53`	Discontinued procedure	Use when testing was started but discontinued prior to completion for documented technical reasons.
`59`	Distinct procedural service	Not in the original list; do not use.
`82`	Assistant surgeon not available	Use rarely; not typically applicable for lab-based `81521` but included when a procedural assistant taxonomy is billed in an unusual workflow.
`62`	Two surgeons	Not typically applicable; used only in rare surgical workflows tied to specimen procurement documentation.
`11`	Office or other outpatient visit	Use as an informational modifier rarely with lab billing in certain payer workflows; generally not used with standalone molecular test codes.
`90`	Reference (duplicate)	Duplicate of above; see earlier `90`.

Taxonomy Code	Specialty	Notes
208100000X	Anatomic Pathology	Pathologists who oversee molecular assay validation and interpretation.
208000000X	Clinical Pathology	Laboratory directors and clinical pathologists supervising molecular testing and quality control.
207L00000X	Molecular Genetic Pathology	Specialists in molecular diagnostics who develop and interpret gene expression assays.
207RP1001X	Hematology/Oncology	Medical oncologists who order the recurrence score to guide systemic therapy.
2083P0800X	Pathology and Laboratory Medicine	Laboratory directors and lab managers responsible for testing operations.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C50.911`	Malignant neoplasm of unspecified site of right female breast	Primary breast cancer diagnosis that commonly prompts `81521` recurrence score testing to guide adjuvant therapy.
`C50.912`	Malignant neoplasm of unspecified site of left female breast	As above for left-sided disease; recurrence score informs chemotherapy decisions.
`C50.611`	Malignant neoplasm of upper-outer quadrant of right female breast	Site-specific invasive breast carcinoma; tumor tissue from this lesion is used for gene expression testing.
`C50.612`	Malignant neoplasm of upper-outer quadrant of left female breast	Site-specific tumor code used for clinical documentation and to justify tumor profiling.
`D05.91`	Unspecified secondary malignant neoplasm of breast	In certain clinical contexts where recurrent or secondary breast tumor tissue is assayed to assess recurrence risk.
`Z85.3`	Personal history of malignant neoplasm of breast	May be used when evaluating risk of recurrence and considering assay utility in recurrent disease settings.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`88305`	Level IV surgical pathology, gross and microscopic examination	Performed on the breast resection specimen to provide histopathologic diagnosis and to select the tissue block sent for `81521` testing.
`88342`	Immunohistochemistry, each antibody (e.g., ER, PR, HER2)	Used to determine receptor status (ER/PR/HER2) that complements the recurrence score in treatment planning.
`87070`	Culture, bacterial; aerobic, outpatient	Data not applicable to this molecular assay workflow; included only when infection testing coincides with specimen processing.
`81210`	BRCA1 gene analysis (if clinically indicated)	May be ordered in parallel for hereditary risk assessment but is a separate genetic test from the tumor recurrence score.
`81479`	Unlisted molecular pathology procedure	Used when a novel or proprietary component of testing is performed that is not fully described by `81521`; supplemental coding in rare cases.

CPT 81490: RA Disease Activity Score from 12-Serum Biomarker Panel

CPT-81493-CORONARY-ARTERY-DISEASE-23-GENE-RT-PCR-RISK-SCORE

CPT 81493: 23-Gene RT-PCR Test with Algorithmic CAD Risk Score

CPT-81500-CA125-HE4-ALGORITHMIC-RISK-SCORE

CPT 81500: CA-125 and HE4 Laboratory Testing with Algorithmic Risk Score

CPT-81503-ALGORITHMIC-LAB-RISK-SCORE-CA125-APOLIPOPROTEIN-A1

CPT 81503: Algorithmic Laboratory Risk Score Using Multiple Biomarkers

CPT-81504-TUMOR-ORIGIN-RNA-EXPRESSION-CLASSIFIER

CPT 81504: RNA Expression Tumor Origin Classifier

CPT-81506-DIABETES-BIOMARKER-PANEL-WITH-RISK-SCORE

CPT 81506: Diabetes Biomarker Panel with Algorithmic Risk Score

CPT-81507-NIPS-CELL-FREE-DNA-TRISOMY-RISK-ANALYSIS

CPT 81507: Non-Invasive Prenatal Screening for Trisomies 13, 18, 21

CPT-81508-PAPP-A-HCG-ALGORITHMIC-RISK-ASSAY

CPT 81508: PAPP–A and hCG Laboratory Assay with Algorithmic Risk Score

CPT-81509-LAB-ALGORITHMIC-RISK-ASSESSMENT-PAPP-A-HCG-DIA

CPT 81509: Laboratory Algorithmic Risk Assessment for PAPP–A, hCG, DIA

CPT-81510-PRENATAL-TRIPLE-MARKER-ALGORITHMIC-RISK-ASSESSMENT

CPT 81510: Prenatal Triple-Analyte Algorithmic Risk Assessment

Showing 1–10 of 41

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

OpenPayer

CPT 81521: mRNA Microarray Breast Cancer Recurrence Score

Sign up for cpt 81521 policy alerts

Billing Code Overview

OpenPayer

CPT 81521: mRNA Microarray Breast Cancer Recurrence Score

Sign up for cpt 81521 policy alerts

Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References