ICD-10 Code D05.9 – Unspecified type of carcinoma in situ of breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D05.9 – Unspecified type of carcinoma in situ of breast
What it is
D05.9 identifies carcinoma in situ of the breast when the specific in situ type is not documented. It means abnormal breast cells are present but have not invaded surrounding tissue.
Clinical signs
Clinical features vary; refer to documentation. This diagnosis is often found on imaging or biopsy, with pathology confirming in situ disease but not naming a more specific breast subtype.
When to use this code
Use D05.9 when the record states carcinoma in situ of the breast and does not specify ductal, lobular, or another type. It is appropriate when pathology or provider documentation supports in situ breast cancer but the subtype remains unspecified. If the report is more specific, code that documented type instead.
Do not use for
Do not use this code for invasive breast cancer, benign breast lesions, or a clearly documented specific carcinoma in situ subtype. Check documentation if the pathology report names a more precise diagnosis.
Coding tip
Code D05.9 only when the provider or pathology leaves the in situ breast type unspecified.