HCPCS code G0204: Deleted mammography code and CPT replacements

Key takeaways

HCPCS code G0204 described bilateral diagnostic mammography including computer-aided detection, and Medicare deleted it effective January 1, 2018.

CMS could not process the new mammography CPT codes in 2017, so Medicare required the G codes for the whole of that year.

G0204 crosswalks to CPT 77066 for a bilateral study, and G0206 crosswalks to CPT 77065 for a unilateral study.

CPT 77067 replaced G0202 for screening mammography, and all three CPT codes bundle CAD when it is performed.

Medicare still requires HCPCS G0279 alongside 77065 or 77066 when diagnostic breast tomosynthesis is performed.

HCPCS code G0204 was the Medicare code for bilateral diagnostic mammography, including computer-aided detection.

Medicare retired it on January 1, 2018, and CPT 77066 took its place. Claims carrying G0204 still surface in audits, legacy charge masters, and old billing templates.

This transition is also widely misreported. Plenty of references date the deletion to 2017, and plenty print the G code to CPT crosswalk backwards. Both errors cost money, because the wrong laterality code either gets denied or gets paid at the wrong rate.

One code from that G series family is still live. Medicare continues to require HCPCS G0279 for diagnostic tomosynthesis, so practices that purged every G code after 2018 have been under-billing it ever since.

HCPCS code G0204: Definition and clinical description

HCPCS code G0204 was a Medicare HCPCS Level II code for bilateral diagnostic mammography, including computer-aided detection (CAD) when performed. It applied to diagnostic mammograms ordered to evaluate a known or suspected breast abnormality, as distinct from routine screening.

HCPCS Level II codes are maintained by the Centers for Medicare and Medicaid Services (CMS). The G series covers Medicare-payable services that had no suitable CPT code at the time.

Much of that series is still in force, from home health recertification under G0179 to breast tomosynthesis. G0204 belonged to a family of three G codes that covered every Medicare mammography service.

Laterality was the detail that decided a G0204 claim. Billing it for a single breast, or confusing it with the screening code G0202, was a common denial source long before the code retired. Practices running structured claims management workflows caught those distinctions at charge entry instead of at remittance.

Code status: G0204 is deleted

G0204 was deleted for Medicare purposes on January 1, 2018. Claims submitted with G0204 for dates of service on or after that date are invalid and will be rejected.

CMS retired the whole G series mammography family at once, through Change Request 10181. The instruction reached contractors in Transmittal R3844CP, issued November 21, 2017 and implemented January 2, 2018. The three deleted codes were:

• G0202 — screening mammography, bilateral, including CAD when performed
• G0204 — diagnostic mammography, including CAD when performed, bilateral
• G0206 — diagnostic mammography, including CAD when performed, unilateral

Note that G0204 and G0206 carried the same descriptor apart from laterality. Both bundled CAD. Neither one was a no-CAD code, though some secondary references still describe G0206 that way.

Why coding references print the wrong date

The AMA published new mammography CPT codes for 2017, and most payers switched to them on January 1 of that year. Medicare did not. CMS could not process the new codes in its claims systems in time. It kept G0202, G0204, and G0206 in force for all of 2017.

That left a single year where the correct mammography code depended entirely on the payer. A 2017 Medicare claim needed a G code. The same service billed to a commercial plan usually needed a CPT code. CMS closed the split a year later, on January 1, 2018.

This matters for anything that reaches back into 2017 dates of service: late claims, appeals, reopenings, and payer audits. It also explains why so many coding references print the wrong date. They took the CPT effective date and assumed Medicare followed on the same day.

Legacy billing templates and older electronic health record configurations may still map mammography services to G0204. The same problem follows other retired screening codes, such as G0106 for colorectal cancer screening. Periodic code audits catch these mappings before the payer does.

G0204 replacement CPT codes: 77065, 77066, and 77067

Each deleted G code maps to one CPT code, and the mapping follows laterality. G0204 was bilateral, so it maps to the bilateral CPT code 77066. G0206 was unilateral, so it maps to 77065.

The crosswalk is one to one, and laterality is what holds it together. For a bilateral study, 77066 is the correct code. For a unilateral study, 77065 applies. Reversing the two is the single most common coding error left over from this transition.

CPT 77067 replaced G0202 for screening mammography. It sits apart from the diagnostic codes and carries its own Medicare eligibility rules. Mixing up screening and diagnostic mammography is one of the most frequent radiology billing errors.

Structured clinical documentation workflows that capture the indication at the point of order cut those mix-ups sharply.

Computer-aided detection (CAD) and mammography billing

CAD was bundled into G0204 through the phrase including CAD when performed. All three replacement CPT codes carry the same phrase, so CAD is bundled across the current code set:

• CPT 77065 — diagnostic mammography, including CAD when performed, unilateral
• CPT 77066 — diagnostic mammography, including CAD when performed, bilateral
• CPT 77067 — screening mammography, bilateral, including CAD when performed

Because CAD is bundled, there is no separate CAD charge to add alongside these codes. The old add-on codes for CAD were deleted when this code set arrived. Billing a CAD line item on top of 77065, 77066, or 77067 produces a bundling edit and a payment reduction.

CAD and tomosynthesis are easy to conflate, and conflating them costs money. CAD is bundled into the mammography code. Tomosynthesis is separately payable and carries its own add-on code.

Tomosynthesis: The mammography G code that survived

The G series did not disappear from mammography billing. HCPCS G0279 remains active, and Medicare still requires it for diagnostic digital breast tomosynthesis. Report one unit in addition to 77065 or 77066, with laterality carried by the primary code.

Medicare does not accept CPT 77061 or 77062 for diagnostic tomosynthesis, even though many commercial plans do. For screening tomosynthesis, the add-on is CPT 77063, reported with 77067. Our reference on G0279 covers the pairing rules in detail.

Practices that dropped every G code from their mammography templates after 2018 often dropped G0279 with them. The result is unbilled tomosynthesis on Medicare claims, month after month, with nothing on the remittance to flag it.

Modifiers that apply to mammography claims

Modifier selection decides both payment and audit exposure. The table below covers the modifiers most often appended to current mammography codes, and the scenario each one answers.

Modifiers GG and GH both describe a screening study that turned diagnostic, so they answer different billing choices. Use GG when both studies are reported. Use GH when only the diagnostic study is reported. Check your Medicare Administrative Contractor guidance, because reporting preferences vary between contractors.

Mammography reimbursement and patient cost sharing

Screening and diagnostic mammography are paid under the same fee schedule but treated very differently at the front desk. Screening is a preventive benefit with no patient cost sharing. Diagnostic mammography is a regular Part B service, so the deductible and coinsurance apply.

Payment amounts change every year and vary by locality, so a national figure is never the number you will be paid. Check the CMS Physician Fee Schedule lookup tool for your own carrier and locality before you quote a patient or forecast revenue.

Frequency limits also drive denials. Medicare covers one baseline screening mammogram for women aged 35 to 39, then one screening every 12 months from age 40. A screening billed 11 months after the last one gets denied on frequency, whatever the code says.

ICD-10 codes that support medical necessity

The diagnosis code is what separates a screening claim from a diagnostic claim in the payer’s eyes. A diagnostic mammogram needs a documented sign, symptom, or prior abnormal finding. A screening mammogram needs the screening encounter code and nothing more.

Always code to the highest available specificity. N63.11 for a lump in the upper outer quadrant of the right breast is far more defensible than an unspecified alternative. Our reference on Z12.31 covers the screening side of that pairing.

Z85.3 needs more care than the rest of the list. Whether it supports a screening or a diagnostic study depends on the order. Surveillance imaging after a procedure such as 19305 usually arrives as a diagnostic order.

Coverage rules for individual diagnoses live in Local Coverage Determinations, which differ between contractors. Check your own contractor’s determination before you assume a diagnosis supports a diagnostic study.

Documentation requirements

Incomplete documentation is the second biggest reason mammography claims fail, behind code selection itself. Every element below should be in the record before the claim goes out.

• Order and clinical indication: The referring provider’s order, plus the sign, symptom, or prior finding that makes the study diagnostic rather than screening.
• Laterality: State which breast was imaged, or that both were. The record has to match 77065 or 77066 on the claim line.
• Views obtained: Document the views performed. Screening mammography under 77067 is defined as a two-view study of each breast.
• Tomosynthesis: Note it separately when it is performed, because the add-on code is billed on its own line.
• Conversion note: When a screening study becomes diagnostic, record the abnormality that prompted the extra views. This is what supports modifier GG or GH.
• Assessment and recommendation: Include the BI-RADS category and the follow-up recommendation in the final report.
• Facility certification: Medicare only pays mammography performed at a facility certified under the Mammography Quality Standards Act. Keep the certificate current and on file.

Templates that prompt for each of these fields at the point of care catch omissions before submission rather than after denial. The order itself usually starts elsewhere, so referring teams on GP practice software should send the indication with it.

Connected EHR and billing integration then keeps the record and the claim line in step.

How to bill diagnostic mammography under Medicare today

Report 77065 for a unilateral diagnostic study and 77066 for a bilateral one, with G0279 added when tomosynthesis is performed. Those are the only valid diagnostic mammography codes for Medicare dates of service from January 1, 2018 onward. G0204 is not accepted.

The rules that decide most Medicare mammography claims:

• Laterality matters: 77065 is unilateral and 77066 is bilateral. The wrong one earns a denial or a payment at the wrong rate.
• Indication documentation: A diagnostic study needs a documented clinical indication, such as a palpable mass or an abnormal screening result. Screening under 77067 instead has age and frequency criteria.
• Same-day conversion is billable: When a screening study converts to diagnostic, both can be reported. Append modifier GG to the diagnostic code and document the abnormality that triggered it.
• CAD is bundled: Never add a separate CAD charge. It is included in every one of the three CPT descriptors.
• Tomosynthesis is not bundled: Medicare wants G0279 with a diagnostic study and 77063 with a screening study. Leaving them off means leaving payment on the table.

Teams handling women’s health billing can find the documentation and coding standards for this population in our overview of OB-GYN practice management.

Medicare vs. commercial payer billing rules for mammography

Medicare adopted CPT 77065, 77066, and 77067 on January 1, 2018, a year after most commercial payers did. That one-year offset still shapes how older claims and appeals have to be coded.

For Medicare, the transition is settled and G0204 is rejected outright. With commercial plans, the deleted G codes are rarely the problem. The risk sits in coverage criteria, prior authorization thresholds, and tomosynthesis coding, which is where the two worlds still diverge.

Common billing errors and denial prevention

Mammography denials follow a short list of patterns, and most of them trace back to this code transition. The table maps each one to its cause and its fix.

Two of these are invisible on a remittance. A missing G0279 and a reversed laterality code both pay, just not correctly. Only an internal audit finds them, which is why quarterly code reviews belong on the revenue cycle calendar.

Coders can confirm a code’s status before it reaches a claim using the AAPC HCPCS code lookup. Building that check into onboarding for new billing staff prevents errors that come from unfamiliarity with historical transitions like this one.

How Pabau keeps mammography coding current

Three things decide whether a mammography claim pays:

• The indication captured when the study is booked
• The laterality written in the radiology report
• The code list the biller works from

When those three live in separate systems, the link between them breaks. The error then reaches the payer unchallenged.

Practice management software like Pabau keeps them in one place. Medical records management holds the order, the indication, and the report together. The person coding the claim can see what was done, and to which breast.

Service-level billing rules then carry the current codes. When a code retires, you change the mapping once instead of hoping every template caught it.

Claims management then tracks each submission through to payment. A pattern like a missing tomosynthesis add-on shows up in a report, instead of staying hidden in the remittance.

For high-volume radiology and women’s health teams, that timing is the whole point. It is the difference between catching a coding problem in this month’s report and catching it in next year’s audit.

Bill mammography with the current code set

Pabau links the imaging order, the clinical note, and the claim line in one workflow. Laterality and add-on codes are right before the claim leaves your practice, so denials drop and payment arrives sooner.

Book a demo

Conclusion

Two things about G0204 are worth carrying away. Medicare retired it on January 1, 2018, not 2017. And it maps to 77066, because both codes describe a bilateral study.

Get those two facts right and the rest of the mammography code set falls into place. Then check that G0279 is still in your Medicare templates. Most of the money going missing on mammography today is lost to a live add-on code, quietly left off the claim.

Fixing this properly means fixing it at the template level, not claim by claim. Book a demo to see how Pabau keeps imaging orders, clinical notes, and claim lines aligned for radiology and women’s health teams.

Continue your research

Need the screening side of this code family? HCPCS code G0202 walks through the deleted screening code and how CPT 77067 took over.

Coding a screening mammogram today? CPT code 77067 sets out the eligibility, frequency, and documentation rules for the screening study.

Pairing the right diagnosis code with a screening claim? ICD-10 code Z12.31 explains how the screening encounter code establishes coverage.

Billing a biopsy after an abnormal mammogram? CPT code 19084 sets out the add-on rules for a breast biopsy in the same session.

Frequently asked questions

Current codes, CAD, and tomosynthesis