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C50.612 ICD-10-CM Code: Malignant neoplasm of axillary tail of left female breast

C50.612 maps to CMS-HCC V28 23. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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Code lookupC50.612

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

C50.612

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

Malignant neoplasm of axillary tail of left female breast

Cancer that develops in the axillary tail (the extension of breast tissue toward the armpit) of the left female breast.

Buddy the Bee presenting code insight

Buddy Insight

Cancer of the axillary tail of the left female breast involves the breast tissue that extends toward the left axilla.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 23

Coefficient HCC 23: 0.186 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

Context needed

HCC 011, HCC 012

Coefficient needs member context

ESRD/PACE

Context needed

HCC 12

Coefficient needs member context

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C50.6Malignant neoplasm of axillary tail of breastC50.61Malignant neoplasm of axillary tail of breast, femaleC50.612Malignant neoplasm of axillary tail of left female breast

Inclusion Terms

Official

No inclusion terms are included in this display for C50.612. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C50.612. Check the code and parent instructions in the Code Book.

Related Codes

Official
C50.611Malignant neoplasm of axillary tail of right female breastC50.619Malignant neoplasm of axillary tail of unspecified female breast

Includes

Official
  • connective tissue of breastInherited from C50
  • Paget's disease of breastInherited from C50
  • Paget's disease of nippleInherited from C50

Excludes 1

Official
  • skin of breast (C44.501, C44.511, C44.521, C44.591)Inherited from C50

Code First

Official

No Code First sequencing instructions are included in this display for C50.612. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify estrogen, and other hormones and factors receptor status (Z17.-)Inherited from C50

Code Also

Official

No Code Also instructions are included in this display for C50.612. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed female patient sex
Laterality documented as left breast
Specific site identified as axillary tail
Lymph node assessment and involvement status

MEAT Support

HCC Buddy guidance
Confirmed female patient sex
Laterality documented as left breast
Specific site identified as axillary tail
Lymph node assessment and involvement status

Audit Caution

HCC Buddy guidance
Confusing axillary tail involvement with axillary lymph node metastasis
Defaulting to upper-outer quadrant code when axillary tail is specifically documented
Overlooking the term 'tail of Spence' as equivalent to axillary tail
Incorrectly using overlapping sites code when the cancer is confined to the axillary tail

Common Mistakes

HCC Buddy guidance
C50.611 — Axillary tail of right female breast; laterality reversal
C50.412 — Upper-outer quadrant of left female breast; axillary tail is distinct from upper-outer quadrant
C77.3 — Secondary malignant neoplasm of axillary lymph nodes; do not confuse primary breast cancer in the axillary tail with lymph node metastasis

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C50.612 an HCC code?

Yes. C50.612 (Malignant neoplasm of axillary tail of left female breast) maps to HCC 23, Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C50.612 is billable and maps to V28 HCC 23, Prostate, Breast, and Other Cancers and Tumors. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C50.612
Description
Malignant neoplasm of axillary tail of left female breast
HCC (V28)
HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF reference coefficient
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors
0.186
RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C50.612 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C50.612

For C50.612, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

C50.612 is the ICD-10-CM diagnosis code for malignant neoplasm of axillary tail of left female breast. Cancer that develops in the axillary tail (the extension of breast tissue toward the armpit) of the left female breast. C50.612 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, C50.612 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. No V24 mapping is shown for C50.612; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

The axillary tail is an important anatomical location as it extends into the armpit region and may involve lymph nodes. For C50.612, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for C50.612 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •The axillary tail is an important anatomical location as it extends into the armpit region and may involve lymph nodes
  • •Verify laterality is documented as 'left' before assigning this code; right-sided tumors require C50.611

Clinical Significance

Cancer of the axillary tail of the left female breast involves the breast tissue that extends toward the left axilla. Due to its proximity to lymphatic drainage pathways, tumors in this location require careful assessment of lymph node involvement and may present diagnostic challenges in distinguishing primary breast tissue malignancy from axillary pathology.

Documentation Requirements

  • ✓Confirmed female patient sex
  • ✓Laterality documented as left breast
  • ✓Specific site identified as axillary tail
  • ✓Lymph node assessment and involvement status
  • ✓Histological type and grade
  • ✓TNM staging
  • ✓Imaging studies confirming axillary tail as the primary site

Commonly Confused Codes

  • •C50.611: Axillary tail of right female breast; laterality reversal
  • •C50.412: Upper-outer quadrant of left female breast; axillary tail is distinct from upper-outer quadrant
  • •C77.3: Secondary malignant neoplasm of axillary lymph nodes; do not confuse primary breast cancer in the axillary tail with lymph node metastasis

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└C50.612Malignant neoplasm of axillary tail of left female breast
└C50.612Malignant neoplasm of axillary tail of left female breast

Also searched as

  • C50 612
  • C50612

For C50.612, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C50.612 maps to CMS-HCC V28 category 23, Prostate, Breast, and Other Cancers and Tumors. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C50.612. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

More on C50.612

Code family

Every C50 code with its CMS-HCC V28 statusMalignant neoplasm of breast, 57 billable codes

Related condition guides

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