Carcinoma in situ of breast

This code signifies the presence of abnormal cells within the milk ducts or lobules of the breast that have not invaded surrounding tissue. It represents a non-invasive form of breast cancer, often considered a precursor to invasive carcinoma.

Use this code when documentation explicitly states "carcinoma in situ of breast," "ductal carcinoma in situ (DCIS)," or "lobular carcinoma in situ (LCIS)." This diagnosis is typically made following a biopsy or surgical excision.

• Distinguish carefully between carcinoma in situ and invasive breast cancer; the latter requires a different code.
• Ensure the pathology report clearly specifies "in situ" to avoid miscoding.
• Do not use this code for atypical hyperplasia, which is a pre-malignant condition but not yet carcinoma in situ.