ICD-10-CM 2027
ICD-10 code for breast disease
From the official ICD-10-CM alphabetic index entry “Disease, diseased › breast”. Page updated September 29, 2026.
About coding breast disease
The ICD-10-CM code for breast disease is N64.9 (Disorder of breast, unspecified). The official index lists 3 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on N64.9.
Within N64, choose N64.9 (Disorder of breast, unspecified) only when documentation doesn't support a more specific option: fissure and fistula of nipple (N64.0), fat necrosis of breast (N64.1), atrophy of breast (N64.2), Galactorrhea not associated with childbirth (N64.3), Mastodynia (N64.4), other signs and symptoms in breast (N64.5) and other specified disorders of breast (N64.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 600 (Non-Malignant Breast Disorders with CC/MCC, relative weight 0.9975) and DRG 601 (Non-Malignant Breast Disorders without CC/MCC, relative weight 0.6017), in MDC 09 (Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific breast disease codes (official index)
Common questions about breast disease ICD-10 codes
What is the ICD-10 code for breast disease?
- N64.9 — Disorder of breast, unspecified. More specific codes apply when the documentation supports them: C50.91, C50.92, N64.89.
Is N64.9 billable?
- Yes. N64.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can N64.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict N64.9 as a principal diagnosis.
Is N64.9 a CC or MCC?
- No. N64.9 is neither a CC nor an MCC under MS-DRG v44.0.