ICD-10 Code D05.90 – Unspecified type of carcinoma in situ of unspecified breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D05.90 – Unspecified type of carcinoma in situ of unspecified breast
What it is
D05.90 identifies carcinoma in situ of the breast when the record does not specify the type or the breast side. It means abnormal cells are confined to the breast ducts or lobules and have not invaded nearby tissue.
Clinical signs
Clinical features vary; refer to documentation. Many cases are found on screening mammography or biopsy rather than by symptoms, and the pathology report should confirm in situ disease.
When to use this code
Use this code when the provider documents carcinoma in situ of the breast but does not name the histologic type or laterality. It may also fit when the chart only states “breast in situ carcinoma” and no further detail is available. Check documentation before assigning a more specific code.
Do not use for
Do not use D05.90 when the record specifies a particular in situ subtype or a definite breast side. Also avoid it for invasive breast cancer, which is coded separately.
Coding tip
Query for pathology details and laterality whenever the note is vague, because a more specific D05 code may be available.