ICD-10 Code D09.3 – Carcinoma in situ of thyroid and other endocrine glands (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D09.3 – Carcinoma in situ of thyroid and other endocrine glands
What it is
This code identifies carcinoma in situ, a noninvasive neoplastic process, involving the thyroid or another endocrine gland. The abnormal cells are confined to the original tissue layer and have not invaded surrounding tissue.
Clinical signs
Clinical features vary; refer to documentation. Diagnosis is usually based on pathology showing in situ malignant change without evidence of invasion.
When to use this code
Use D09.3 when the provider documents carcinoma in situ of the thyroid or another endocrine gland and pathology supports a noninvasive lesion. Apply it for confirmed in situ disease, not for suspected malignancy or invasive cancer. If the endocrine gland is not specified, check documentation.
Do not use for
Do not use this code for invasive endocrine malignancies, benign nodules, or uncertain masses. If the record only says “rule out” or “possible” carcinoma, check documentation before coding.
Coding tip
Match the code to both the site and the in situ wording in the pathology report.