C31 – Malignant neoplasm of accessory sinuses
ICD-10-CM 2027 diagnosis code · Malignant neoplasms of respiratory and intrathoracic organs
ICD-10-CM code
C31
- Code
C31(claims format:C31)- Description
- Malignant neoplasm of accessory sinuses
- Billable
- No – use a more specific code below
- Valid for
- Dates of service October 1, 2026 – September 30, 2027 (FY2027)
- Chapter
- 2. Neoplasms (C00-D49)
- Block
- C30-C39 Malignant neoplasms of respiratory and intrathoracic organs
Billable codes under C31
C31 is a header code and cannot be used on claims. Choose the most specific code:
- C31.0 – Malignant neoplasm of maxillary sinusBillable
- C31.1 – Malignant neoplasm of ethmoidal sinusBillable
- C31.2 – Malignant neoplasm of frontal sinusBillable
- C31.3 – Malignant neoplasm of sphenoid sinusBillable
- C31.8 – Malignant neoplasm of overlapping sites of accessory sinusesBillable
- C31.9 – Malignant neoplasm of accessory sinus, unspecifiedBillable
Notes inherited from parent codes
Instructional notes at a category or block level apply to every code below it.
Block C30-C39
Includes:
- malignant neoplasm of middle ear
Excludes1 (not coded here):
- mesothelioma (C45.-)
Frequently asked questions
What is ICD-10 code C31?
C31 is the ICD-10-CM code for malignant neoplasm of accessory sinuses, in the block C30-C39 (Malignant neoplasms of respiratory and intrathoracic organs).
Is C31 a billable code?
No. C31 is a header code with more specific child codes; report one of the billable codes listed above.
Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.