C31: Malignant neoplasm of accessory sinuses
Codes under C31 (Malignant neoplasm of accessory sinuses). A ✓ marks a billable (fully specified) code; category codes without a ✓ are not billable on their own.
| Code | Description | Billable |
|---|---|---|
| C31.0 | Malignant neoplasm of maxillary sinus | ✓ |
| C31.0 | Malignant neoplasm of maxillary sinus | ✓ |
| C31.1 | Malignant neoplasm of ethmoidal sinus | ✓ |
| C31.1 | Malignant neoplasm of ethmoidal sinus | ✓ |
| C31.2 | Malignant neoplasm of frontal sinus | ✓ |
| C31.2 | Malignant neoplasm of frontal sinus | ✓ |
| C31.3 | Malignant neoplasm of sphenoid sinus | ✓ |
| C31.3 | Malignant neoplasm of sphenoid sinus | ✓ |
| C31.8 | Malignant neoplasm of overlapping sites of accessory sinuses | ✓ |
| C31.8 | Malignant neoplasm of overlapping sites of accessory sinuses | ✓ |
| C31.9 | Malignant neoplasm of accessory sinus, unspecified | ✓ |
| C31.9 | Malignant neoplasm of accessory sinus, unspecified | ✓ |
Frequently asked questions
What is ICD-10-CM code C31?
C31 is an ICD-10-CM category covering Malignant neoplasm of accessory sinuses. It contains 12 more specific diagnosis codes, 12 of which are billable.
Is C31 a billable code?
No — C31 is a category header and isn't billable on its own. Code to the highest level of specificity using one of its subcodes (for example C31.0 — Malignant neoplasm of maxillary sinus). 12 of the 12 codes under C31 are billable.
What codes fall under C31?
C31 includes C31.0, C31.0, C31.1, C31.1, C31.2, plus 7 more. See the full list with descriptions and billable status above.
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Informational only, not coding or medical advice. Verify against the official ICD-10-CM (FY2026) and your payer's guidelines.
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