C31.9 — Malignant neoplasm of accessory sinus, unspecified
Is C31.9 billable?
Yes, but C31.9 is an unspecified code. C31.9 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, C31.9 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting C31.9 — the more specific alternatives are listed below.
C31.9 at a glance
| Code | C31.9 |
|---|---|
| Description | Malignant neoplasm of accessory sinus, unspecified |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does C31.9 group to?
C31.9 sits in MDC Pre and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 011Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with MCCsurgical
- 012Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with CCsurgical
- 013Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy without CC/MCCsurgical
Excludes1 — never code together — inherited from C30-C39
The conditions below can never be reported together with C31.9 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- mesothelioma (C45.-)
How long has C31.9 existed?
C31.9 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.