ICD-10 Code C38.3 – Malignant neoplasm of mediastinum, part unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C38.3 – Malignant neoplasm of mediastinum, part unspecified
What it is
C38.3 identifies a malignant tumor arising in the mediastinum when the exact mediastinal site is not specified. Use it when documentation confirms a cancer in this central chest compartment but does not name a more precise location.
Clinical signs
Clinical features vary; refer to documentation. Mediastinal cancers may present with chest pain, cough, dyspnea, or compression symptoms, but the diagnosis should be supported by imaging, pathology, or a clear provider statement.
When to use this code
Use this code when the record states malignant neoplasm of the mediastinum and no subsite is identified. It is appropriate for confirmed primary or unspecified mediastinal malignancy when you cannot assign a more specific ICD-10-CM code. If the note names a different primary site with mediastinal spread, code the primary cancer and any documented secondary sites.
Do not use for
Do not use C38.3 for benign mediastinal masses or for metastatic disease when the mediastinum is only a secondary site. Check documentation if the provider identifies a more specific mediastinal structure.
Coding tip
Query for the exact mediastinal subsite before defaulting to C38.3.