Summary & Overview
HCPCS G9831: AJCC Stage II or III at Breast Cancer Diagnosis
HCPCS Level II code G9831 captures patients whose breast cancer was staged as AJCC Stage II or III at diagnosis. Accurate staging codes support quality measurement, care coordination, and population-level monitoring of cancer severity, with implications for treatment planning and outcomes tracking. Nationally, standardized reporting of stage at diagnosis informs payer quality programs, cancer registries, and value-based care initiatives.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code’s clinical meaning and typical sites of service, descriptions of payer coverage patterns, and benchmarking context where available. The publication outlines how G9831 is used within quality reporting and registry workflows, summarizes common billing modifiers when present in data feeds, and highlights gaps where data were not provided.
This summary provides clinicians, coders, and policy analysts with the clinical context and billing implications of G9831, enabling clearer communication between oncology teams, billing staff, and payers about stage-based reporting. Data not available in the input are noted where applicable.
Billing Code Overview
HCPCS Level II code G9831 denotes AJCC stage at breast cancer diagnosis = II or III. This code is used to indicate that at initial diagnosis the patient’s breast cancer was classified as Stage II or Stage III according to the American Joint Committee on Cancer (AJCC) staging criteria.
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Service type: Quality/staging data reporting derived from diagnostic and pathology assessment
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Typical site of service: Oncology clinics, hospital outpatient departments, cancer centers, and other settings where breast cancer staging is documented
Clinical & Coding Specifications
Clinical Context
A 54-year-old woman presents to a multidisciplinary breast cancer clinic after an abnormal screening mammogram and core needle biopsy confirming invasive ductal carcinoma. Staging workup including diagnostic mammography, breast MRI, chest imaging, and sentinel lymph node biopsy leads the oncology team to assign an American Joint Committee on Cancer (AJCC) clinical stage of II or III at diagnosis. The coding descriptor G9831 — “Ajcc stage at breast cancer diagnosis = ii or iii” — is used to capture documentation of stage II or III disease for quality reporting and registry abstraction.
The clinical workflow begins with diagnostic confirmation by pathology, radiologic staging, surgical consultation for local disease management, and medical oncology evaluation for systemic therapy. Documentation of AJCC stage (tumor size, nodal status, and presence/absence of metastasis) is recorded in the patient’s problem list, pathology report, operative note, and oncology consultation. This stage designation informs treatment planning such as neoadjuvant chemotherapy, mastectomy versus breast-conserving surgery, axillary staging procedures, and radiation therapy planning. Coding staff, cancer registrars, and quality reporting teams use the G9831 indicator to denote patients diagnosed with AJCC stage II or III breast cancer for performance metrics, payor reporting, and registry submission.
Coding Specifications
| Modifier | Description | When to Use |
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