ICD-10 Code C31.1 – Malignant neoplasm of ethmoidal sinus (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C31.1 – Malignant neoplasm of ethmoidal sinus
What it is
C31.1 identifies a malignant tumor arising in the ethmoidal sinus, one of the air-filled spaces between the nose and the eyes. Use it when the record documents primary cancer of that sinus.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings may include nasal obstruction, epistaxis, facial pressure, or symptoms related to local spread, but diagnosis should be supported by imaging or pathology.
When to use this code
Use C31.1 when the provider documents primary malignant neoplasm of the ethmoidal sinus, including confirmed cancer of that site. You may also use it when the chart clearly specifies ethmoid sinus as the primary location. If the record only says sinus cancer without a site, check documentation.
Do not use for
Do not use this code for benign ethmoid sinus lesions, inflammatory sinus disease, or metastatic disease to the sinus from another primary site. If the documentation is unclear, check documentation.
Coding tip
Code the documented primary site exactly; ethmoidal sinus is specific and should not be substituted with a general sinus code.