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ICD-10-CM 2027 diagnosis code

C31Malignant neoplasm of accessory sinuses

Not billable — use a more specific code

C31 is a header code, so it can't be reported by itself. Choose one of the 6 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About C31

C31 is the ICD-10-CM diagnosis code for malignant neoplasm of accessory sinuses. It belongs to block C30-C39 (malignant neoplasms of respiratory and intrathoracic organs) and chapter 2 (neoplasms). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: C31.0 (sinus), C31.1 (sinus), C31.2 (sinus), C31.3 (sinus), C31.8 (sinuses) and C31.9 (unspecified).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under C31

Notes that apply from higher levels

Instructions written at a parent level also apply to C31.

Broader instructions also apply from C30-C39 Malignant neoplasms of respiratory and intrathoracic organs and Chapter 2: Neoplasms.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about C31

Is C31 billable?

No. C31 is a header code. Report one of its more specific subcodes instead.