2026 ICD-10-CM Diagnosis Code C79.81Secondary malignant neoplasm of breast

ICD-10-CM Codes›C00–D49›C76-C80›C79

ICD-10-CM C79.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C79.81 is a billable ICD-10-CM diagnosis code for secondary malignant neoplasm of breast. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 582 through 583, 597 through 599. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Secondary malignancies.

Code Identity

ICD-10-CM Code
C79.81
Billable Status
Yes — Valid for Submission
Code Describes
Secondary malignant neoplasm of breast
Short Description
Secondary malignant neoplasm of breast
Same as the full description in the CMS dataset.
Parent Code
C79.8
Secondary malignant neoplasm of other specified sites

Code Classification

ChapterC00–D49Neoplasms
SectionC76-C80Malignant neoplasms of ill-defined, other secondary and unspecified sites
CategoryC79Secondary malignant neoplasm of other and unspecified sites
This CodeC79.81Secondary malignant neoplasm of breast

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Adenocarcinoma of breast
  • Bilateral metastatic malignant neoplasm to breasts
  • Malignant neoplasm of areola
  • Malignant neoplasm of bone, connective tissue, skin and breast
  • Malignant neoplasm of ectopic site of breast
  • Malignant neoplasm of nipple
  • Metaplastic carcinoma of breast
  • Metastatic carcinoma to axillary tail of breast
  • Metastatic carcinoma to bone, connective tissue, skin and breast
  • Metastatic carcinoma to breast
  • Metastatic carcinoma to lower inner quadrant of breast
  • Metastatic carcinoma to lower outer quadrant of breast
  • Metastatic carcinoma to upper inner quadrant of breast
  • Metastatic carcinoma to upper outer quadrant of breast
  • Metastatic infiltrating duct carcinoma to breast
  • Metastatic malignant neoplasm to areola
  • Metastatic malignant neoplasm to axillary tail of breast
  • Metastatic malignant neoplasm to breast
  • Metastatic malignant neoplasm to central portion of breast
  • Metastatic malignant neoplasm to ectopic site of breast
  • Metastatic malignant neoplasm to left breast
  • Metastatic malignant neoplasm to lower inner quadrant of breast
  • Metastatic malignant neoplasm to lower outer quadrant of breast
  • Metastatic malignant neoplasm to nipple
  • Metastatic malignant neoplasm to right breast
  • Metastatic malignant neoplasm to upper inner quadrant of breast
  • Metastatic malignant neoplasm to upper outer quadrant of breast
  • Metastatic metaplastic carcinoma to breast
  • Metastatic scirrhous carcinoma to breast
  • Neoplasm of areola
  • Neoplasm of ectopic site of breast
  • Scirrhous carcinoma of breast

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Melanoma(malignant)
      • metastatic
        • breast

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO070
Secondary malignancies
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary		Malig.
Secondary		Ca
in situ		BenignUncertainUnspec.
areolaC50.0C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts)C50.9C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › areolaC50.0C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › axillary tailC50.6C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › central portionC50.1C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › innerC50.8C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › lowerC50.8C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › lower-inner quadrantC50.3C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › lower-outer quadrantC50.5C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › mastectomy site (skin) [See Also: Neoplasm, breast, skin] › specified as breast tissueC50.8C79.81––––
breast (connective tissue) (glandular tissue) (soft parts) › midlineC50.8C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › nippleC50.0C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › outerC50.8C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › tail (axillary)C50.6C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › upperC50.8C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › upper-inner quadrantC50.2C79.81D05.D24.D48.6D49.3
breast (connective tissue) (glandular tissue) (soft parts) › upper-outer quadrantC50.4C79.81D05.D24.D48.6D49.3
mastectomy site (skin) [See Also: Neoplasm, breast, skin] › specified as breast tissueC50.8C79.81––––
nippleC50.0C79.81D05.D24.––
skin NOS › mastectomy site (skin) [See Also: Neoplasm, skin, breast] › specified as breast tissueC50.8C79.81––––

Patient EducationClinical

Breast Cancer

Breast cancer is a cancer that starts in breast tissue. It happens when cells in the breast change and grow out of control. New cells grow even when you don't need them, and old cells don't die when they should. These extra cells can form a mass called a tumor.

The full article covers:

  • What is breast cancer?
  • What are the types of breast cancer?
  • What causes breast cancer?
  • Who is at risk for breast cancer?
  • What are the signs and symptoms of breast cancer?
  • How is breast cancer diagnosed?
  • What are the treatments for breast cancer?
  • Can breast cancer be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C79.81 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
198.81 Second malig neo breast
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C79.81Overview

Is C79.81 (Secondary malignant neoplasm of other specified sites) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report secondary malignant neoplasm of breast on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C79.81 group to?

When secondary malignant neoplasm of breast is the principal diagnosis on an inpatient stay, it groups to MS-DRG 582, 583, 597, 598, 599, with relative weights from 0.7332 to 1.9266 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C79.81?

Under the General Equivalence Mappings, secondary malignant neoplasm of breast converts to ICD-9-CM 198.81 (second malig neo breast). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.