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C50.619 ICD-10-CM Code: Malignant neoplasm of axillary tail of unspecified female breast

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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of breast (C50)

C50.619

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of axillary tail of unspecified female breast

Cancer in the axillary tail of a female breast when the specific side (left or right) is not documented or unknown.

Buddy the Bee presenting code insight

Buddy Insight

This unspecified laterality code for axillary tail breast cancer in females should prompt a provider query.

CMS-HCC V28

HCC 22

RAF 0.363

CMS-HCC V24

HCC 12

RAF 0.150

ACA/HHS

N/A

—

Not mapped

ESRD/PACE

HCC 12

RAF 0.045

RXHCC

HCC 22

RAF 0.124

Code Book Path

Official
C50.6Malignant neoplasm of axillary tail of breast
C50.61Malignant neoplasm of axillary tail of breast, female
C50.619Malignant neoplasm of axillary tail of unspecified female breast

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C50.619 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C50.619 in this effective period.

Related Child Codes

Official
C50.611Malignant neoplasm of axillary tail of right female breast
C50.612Malignant neoplasm of axillary tail of left female breast

Includes

Official

ICD-10-CM does not list Includes notes for C50.619 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C50.619 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C50.619 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C50.619 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C50.619 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed female patient sex
Site confirmed as axillary tail
Clinical justification for unspecified laterality
Evidence of query attempt for laterality clarification

MEAT Support

HCC Buddy guidance
Confirmed female patient sex
Site confirmed as axillary tail
Clinical justification for unspecified laterality
Evidence of query attempt for laterality clarification

Audit Caution

HCC Buddy guidance
Accepting unspecified laterality without reviewing imaging, surgical, or pathology reports
This code should trigger a compliance review if used frequently in a coding practice
Not querying the provider for laterality specification before finalizing the code

Common Mistakes

HCC Buddy guidance
C50.611 — Axillary tail of right female breast; use when right is confirmed
C50.612 — Axillary tail of left female breast; use when left is confirmed
C50.919 — Unspecified site of unspecified female breast; even more nonspecific

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is C50.619 an HCC code?

Yes. C50.619 (Malignant neoplasm of axillary tail of unspecified female breast) maps to Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Breast, Prostate, and Other Cancers and Tumors under V24), with a community non-dual aged RAF of 0.363. It is billable for payment year 2026.

Coder answer: C50.619 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C50.619
Description
Malignant neoplasm of axillary tail of unspecified female breast
HCC (V28)
HCC 22 — Bladder, Colorectal, and Other Cancers
RAF
0.363
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 22, Bladder, Colorectal, and Other Cancers
0.363
V24HCC 12, Breast, Prostate, and Other Cancers and Tumors
0.150
ESRDHCC 12, Breast, Prostate, and Other Cancers and Tumors
0.045
RxHCCHCC 22, Cancer, Other Specified Sites
0.124

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work C50.619 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C50.619

For C50.619to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C50.619 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

C50.619 is the ICD-10-CM diagnosis code for malignant neoplasm of axillary tail of unspecified female breast. Cancer in the axillary tail of a female breast when the specific side (left or right) is not documented or unknown. C50.619 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of breast (c50).

Under the CMS-HCC V28 risk adjustment model, C50.619 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.363. Under the older CMS-HCC V24 model, C50.619 maps to Breast, Prostate, and Other Cancers and Tumors (HCC 12) with a community, non-dual, aged base RAF weight of 0.150. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Use this code only when laterality cannot be determined from documentation; if known, use C50.611 or C50.612. Because C50.619 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C50.619 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use this code only when laterality cannot be determined from documentation; if known, use C50.611 or C50.612
  • •Query the provider if laterality is not specified, as it affects staging and treatment planning

Clinical Significance

This unspecified laterality code for axillary tail breast cancer in females should prompt a provider query. The axillary tail is a clinically important anatomical landmark, and laterality is almost always determinable from physical examination, imaging, or surgical documentation. Unspecified codes in this context suggest incomplete record review.

Documentation Requirements

  • ✓Confirmed female patient sex
  • ✓Site confirmed as axillary tail
  • ✓Clinical justification for unspecified laterality
  • ✓Evidence of query attempt for laterality clarification
  • ✓Available imaging or pathology reports reviewed

Commonly Confused Codes

  • •C50.611: Axillary tail of right female breast; use when right is confirmed
  • •C50.612: Axillary tail of left female breast; use when left is confirmed
  • •C50.919: Unspecified site of unspecified female breast; even more nonspecific

Child Codes

C50.611Malignant neoplasm of axillary tail of right female breast
HCC 22
C50.612Malignant neoplasm of axillary tail of left female breast
HCC 22
C50.619Malignant neoplasm of axillary tail of unspecified female breast
HCC 22

Code Hierarchy

└C50Malignant neoplasm of breast└C50.6Malignant neoplasm of axillary tail of breast└C50.61Malignant neoplasm of axillary tail of breast, female└C50.619Malignant neoplasm of axillary tail of unspecified female breast
└C50.619Malignant neoplasm of axillary tail of unspecified female breast

Because C50.619 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

C50.619 maps to CMS-HCC V28 category 22, Bladder, Colorectal, and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works.

More on C50.619

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