Mammography, a vital screening tool in the early detection of breast cancer, is typically billed using CPT codes and HCPCS Level II (G codes). However, the correct use of G codes for mammograms—particularly for Medicare beneficiaries—is often a source of confusion for healthcare providers and billing teams.
In this comprehensive guide, we’ll explore:
- The difference between CPT and G codes for mammography
- Specific G codes used for screening and diagnostic mammograms
- CPT codes that apply to commercial payers
- Billing scenarios and documentation tips
- Common errors and how to avoid claim denials
Why Are There G Codes for Mammograms?
G codes are HCPCS Level II codes used by CMS (Centers for Medicare & Medicaid Services) to identify Medicare-specific procedures. For mammography, Medicare requires providers to use G codes instead of certain CPT codes. These G codes offer more specificity for digital mammography and computer-aided detection (CAD), which are now standard practices.
While CPT codes are typically used for commercial insurance, Medicare mandates the use of G codes when billing for screening or diagnostic mammograms.
CPT Codes for Mammography (Commercial Insurance)
For private payers, mammography procedures are generally billed using the following CPT codes:
- 77067 – Screening mammography, bilateral (2-view study of each breast), including CAD when performed.
- 77066 – Diagnostic mammography, bilateral, including CAD when performed.
- 77065 – Diagnostic mammography, unilateral, including CAD when performed.
These codes replace older codes 77055–77057 and CAD add-on codes 77051–77052, which were deleted in 2018.
G Codes for Mammography (Medicare Billing)
Medicare does not accept CPT codes 77065–77067. Instead, it requires providers to use the following G codes:
1. G0202
Description: Screening mammography, bilateral (2-view study of each breast), digital, including CAD when performed.
Use: For routine annual breast cancer screening for asymptomatic Medicare patients.
2. G0204
Description: Diagnostic mammography, bilateral, digital, including CAD when performed.
Use: When a Medicare patient requires diagnostic follow-up for an abnormal screening result or presents with breast symptoms.
3. G0206
Description: Diagnostic mammography, unilateral, digital, including CAD when performed.
Use: For Medicare patients needing diagnostic imaging of one breast.
When to Use G Codes vs. CPT Codes
| Payer Type | Screening | Diagnostic (Unilateral) | Diagnostic (Bilateral) |
| Medicare | G0202 | G0206 | G0204 |
| Commercial Payers | 77067 | 77065 | 77066 |
Knowing your payer is key. Submitting a CPT code to Medicare may result in claim rejection, and vice versa.
Key Billing and Documentation Considerations
1. Screening vs. Diagnostic Mammogram
- Screening is for asymptomatic women and is typically allowed once every 12 months for Medicare patients over 40.
- Diagnostic mammograms are used when a patient has symptoms, abnormal findings, or a prior history of breast cancer.
Make sure the medical necessity for diagnostic procedures is clearly documented.
2. Modifier Use
For cases where a screening turns into a diagnostic exam on the same day:
Use modifier -GG (Performance and payment of a screening mammogram and diagnostic mammogram on the same day).
Use modifier -GH when a diagnostic mammogram is performed in place of a screening due to findings.
Example:
G0202 (screening) + G0204-GG (diagnostic on same day).
3. Frequency and Coverage Rules
Medicare generally covers:
- One screening mammogram every 12 months for women 40 and older.
- One baseline mammogram for women 35–39.
Diagnostic mammograms are covered as medically necessary with no frequency limitations.
Avoiding Common Coding Errors
Incorrect coding or mismatched modifiers can lead to denials, underpayments, or audit flags. Avoid these common mistakes:
- Using CPT 77067 for Medicare – Medicare requires G0202.
- Missing modifiers when both screening and diagnostic services are provided.
- Incorrect laterality – always confirm whether the mammogram is unilateral or bilateral.
- Inadequate documentation of symptoms or abnormal findings to justify diagnostic codes.
Real-World Coding Scenarios
Scenario 1: Medicare Screening Mammogram
- Patient: Female, age 65, asymptomatic, annual mammogram
- Correct Code: G0202
Scenario 2: Medicare Diagnostic Follow-Up
- Patient: Female, age 67, follow-up of prior abnormal mammogram
- Correct Code: G0204 (bilateral diagnostic)
Scenario 3: Commercial Payer Diagnostic
- Patient: Female, age 45, lump in right breast
- Correct Code: 77065 (unilateral diagnostic)
Scenario 4: Screening and Diagnostic Same Day
- Patient: Medicare patient, screening scheduled, abnormality detected, additional imaging performedCodes:
- G0202 (screening)
- G0204-GG (diagnostic)
Tips for Revenue Cycle Management (RCM) and Compliance
For medical billing services and revenue cycle management (RCM) companies, mastering mammography codes is crucial for:
- Reducing denials
- Ensuring compliance with Medicare policies
- Maximizing reimbursement
Avoiding overpayments and audits
Integrating proper coding workflows, payer-specific rules, and coder training ensures better claim accuracy.
Outsourcing medical coding services to experienced professionals can help healthcare providers maintain compliance and focus on patient care while improving cash flow.
Final Thoughts
Accurate use of G codes for mammograms and CPT mammography codes is more than just checking the box—it ensures proper reimbursement, compliance with payer rules, and efficient healthcare delivery. By understanding the distinction between Medicare G codes and commercial CPT codes, and applying the right modifiers and documentation, providers can avoid costly billing errors and denials.
Whether you’re a solo radiologist, part of a multi-specialty clinic, or working with an RCM company, staying updated on mammography billing codes is critical to your success.
FAQs
1. What is the 77066 CPT code description?
CPT code 77066 describes a diagnostic mammography, including computer-aided detection (CAD), bilateral. It is used when both breasts are imaged for diagnostic purposes due to symptoms such as lumps, pain, or follow-up from an abnormal screening result.
2. What does CPT code 77065 describe?
CPT code 77065 is for a diagnostic mammography, including CAD, unilateral. It is billed when only one breast requires a diagnostic evaluation, often due to targeted symptoms or past abnormalities on one side.
3. What is the 77067 CPT code description?
CPT code 77067 refers to a screening mammography, bilateral, which includes CAD. This code is used for routine breast cancer screening when the patient has no symptoms and both breasts are imaged as part of preventive care.
4. What does HCPCS code G0279 describe?
G0279 is used for diagnostic digital breast tomosynthesis (DBT), unilateral or bilateral, performed in conjunction with a diagnostic mammography (77065 or 77066). It covers additional 3D imaging needed to further evaluate abnormalities detected during diagnostic breast exams.
5. What is the GH modifier description?
The GH modifier indicates diagnostic mammography converted from a screening mammography. It is used when a routine screening (77067) detects an abnormality during the visit and the service must be reclassified as diagnostic.
6. When should 77066 be billed instead of 77065?
Use 77066 for bilateral diagnostic imaging and 77065 for unilateral diagnostic imaging. Both codes include CAD and are chosen based on whether one or both breasts require evaluation.
7. Can G0279 be billed with both 77065 and 77066?
Yes. G0279 is specifically designed to be billed with diagnostic mammography codes 77065 or 77066 when digital breast tomosynthesis is performed as part of diagnostic evaluation.