C31.9
BillableMalignant neoplasm of accessory sinus, unspecified
HCC Category Mapping
V28HCC 21 — Breast, Prostate, Colorectal and Other Cancers and Tumors
0.545V24HCC 11 — Colorectal, Bladder, and Other Cancers
0.306ESRDHCC 11 — Colorectal, Bladder, and Other Cancers
0.000RxHCCHCC 22 — Cancer, Other Specified Sites
0.000What This Code Means
Cancer of the accessory sinuses when the specific sinus location cannot be determined or is not documented.
Coding Tips
- •This is a default code used when documentation does not specify which accessory sinus is affected
- •Query the provider if possible to obtain more specific anatomical location for better clinical specificity
Clinical Significance
Unspecified accessory sinus cancer is used when paranasal sinus malignancy is confirmed but the specific sinus (maxillary, ethmoidal, frontal, sphenoid) cannot be determined. This code represents a documentation gap that should trigger a provider query, as treatment planning and prognosis vary by sinus location.
Documentation Requirements
- ✓Pathology confirmation of sinus malignancy
- ✓Evidence that provider was queried for sinus specificity
- ✓Imaging reviewed for anatomical detail
- ✓Documentation explaining why specific sinus cannot be identified
- ✓Treatment status and disease stage
Commonly Confused Codes
C31.0 — Maxillary sinus: Most common sinus cancer site; review imaging before defaulting to unspecifiedC31.8 — Overlapping sinus sites: Use when multiple sinuses are clearly involvedC30.0 — Nasal cavity: Ensure the tumor is in a sinus, not the nasal cavity properC76.0 — Malignant neoplasm of head, face, and neck: Even less specific; use C31.9 when sinus origin is confirmed
Code Hierarchy
└C31Malignant neoplasm of accessory sinuses└C31.9Malignant neoplasm of accessory sinus, unspecified
└C31.9Malignant neoplasm of accessory sinus, unspecified