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ICD-10/C79.81

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

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Inpatient Payment Groups (MS-DRG)

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43.0 (FY2026), Appendix B.

  • MS-DRG 582 — MASTECTOMY FOR MALIGNANCY WITH CC/MCC (MDC 09)
  • MS-DRG 583 — MASTECTOMY FOR MALIGNANCY WITHOUT CC/MCC (MDC 09)
  • MS-DRG 597 — MALIGNANT BREAST DISORDERS WITH MCC (MDC 09)
  • MS-DRG 598 — MALIGNANT BREAST DISORDERS WITH CC (MDC 09)
  • MS-DRG 599 — MALIGNANT BREAST DISORDERS WITHOUT CC/MCC (MDC 09)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 18 — Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid (supersedes HCC 19, HCC 20, HCC 21, HCC 22, HCC 23)

Other models: CMS-HCC V22 HCC 10 · RxHCC V08 HCC 18

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Code Set: Valid FY2026 and FY2027. FY2026 took effect October 1, 2025.

Official Registry Overview & Definition

Secondary malignant neoplasm of breast is a billable ICD-10-CM diagnosis code (C79.81).

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for C79.81 in the official ICD-10-CM tabular list.

Excludes1 — Not Coded Here

Conditions that can never be reported with this code; the two are mutually exclusive.

  • secondary carcinoid tumors (C7B.-)
  • secondary neuroendocrine tumors (C7B.-)

Nearest Codes in This Family

Official ICD-10-CM classifications closest to C79.81 in its code family, with their registry titles.

  • C79.63 — Secondary malignant neoplasm of bilateral ovaries
  • C79.7 — Secondary malignant neoplasm of adrenal gland
  • C79.70 — Secondary malignant neoplasm of unspecified adrenal gland
  • C79.71 — Secondary malignant neoplasm of right adrenal gland
  • C79.72 — Secondary malignant neoplasm of left adrenal gland
  • C79.8 — Secondary malignant neoplasm of other specified sites
  • C79.82 — Secondary malignant neoplasm of genital organs
  • C79.83 — Secondary malignant neoplasm of oral cavity
  • C79.89 — Secondary malignant neoplasm of other specified sites
  • C79.9 — Secondary malignant neoplasm of unspecified site

View all codes in the C79 family

Indexed Clinical Terms (1)

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code.

  • Melanoma (malignant), metastatic, breast

Neoplasm Table Sites (29)

Anatomical sites from the official ICD-10-CM Table of Neoplasms that map to this code, with the matching behavior column.

  • Neoplasm, neoplastic, abdomen, abdominal — Malignant, Secondary
  • Neoplasm, neoplastic, abdomen, abdominal, cavity — Malignant, Secondary
  • Neoplasm, neoplastic, abdomen, abdominal, organ — Malignant, Secondary
  • Neoplasm, neoplastic, abdomen, abdominal, viscera — Malignant, Secondary
  • Neoplasm, neoplastic, abdomen, abdominal, wall, connective tissue — Malignant, Secondary
  • Neoplasm, neoplastic, abdominopelvic — Malignant, Secondary
  • Neoplasm, neoplastic, alveolar, ridge or process, carcinoma — Malignant, Secondary
  • Neoplasm, neoplastic, alveolar, ridge or process, carcinoma, lower — Malignant, Secondary
  • Neoplasm, neoplastic, alveolar, ridge or process, carcinoma, upper — Malignant, Secondary
  • Neoplasm, neoplastic, areola — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts) — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), areola — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), axillary tail — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), central portion — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), inner — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), lower — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), lower-inner quadrant — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), lower-outer quadrant — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), mastectomy site (skin), specified as breast tissue — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), midline — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), nipple — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), outer — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), tail (axillary) — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), upper — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), upper-inner quadrant — Malignant, Secondary
  • Neoplasm, neoplastic, breast (connective tissue) (glandular tissue) (soft parts), upper-outer quadrant — Malignant, Secondary
  • Neoplasm, neoplastic, mastectomy site (skin), specified as breast tissue — Malignant, Secondary
  • Neoplasm, neoplastic, nipple — Malignant, Secondary
  • Neoplasm, neoplastic, skin NOS, mastectomy site (skin), specified as breast tissue — Malignant, Secondary