ICD-10 Code D05.00 – Lobular carcinoma in situ of unspecified breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D05.00 – Lobular carcinoma in situ of unspecified breast
What it is
D05.00 identifies lobular carcinoma in situ (LCIS) found in the breast when the laterality is not documented. LCIS is a noninvasive breast lesion, meaning the abnormal cells remain in the lobules and have not invaded surrounding tissue.
Clinical signs
LCIS is often discovered incidentally on breast biopsy rather than by a palpable mass or obvious symptoms. Clinical features vary; refer to documentation, especially imaging, pathology, and whether the lesion is described as classic or pleomorphic.
When to use this code
Use D05.00 when the pathology report states lobular carcinoma in situ and does not specify the right or left breast. This code fits documentation of LCIS confirmed by biopsy or excision, with no invasive cancer described. If the record names a specific breast, choose the laterality-specific code instead.
Do not use for
Do not use this code for invasive lobular carcinoma, ductal carcinoma in situ, or atypical lobular hyperplasia. If the documentation is unclear about the site or diagnosis, check documentation before assigning a code.
Coding tip
Code from the pathology report and verify laterality; unspecified breast should be used only when the record truly lacks that detail.