C09.0
BillableMalignant neoplasm of tonsillar fossa
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
0.000What This Code Means
Cancer that develops in the tonsillar fossa, which is the pocket-like area where the tonsil sits in the throat.
Coding Tips
- •Confirm tonsillar fossa location is documented to distinguish from tonsillar pillar cancers
- •Document laterality (left or right) when specified
Clinical Significance
Malignant neoplasm of the tonsillar fossa is one of the most common oropharyngeal cancers, with increasing incidence due to human papillomavirus (HPV) infection. HPV-positive tonsillar cancers have a markedly better prognosis than HPV-negative tumors, making HPV status documentation critical for accurate prognostication and treatment planning.
Documentation Requirements
- ✓Pathology-confirmed malignancy with histological type
- ✓HPV/p16 status documented (critical for prognosis and treatment decisions)
- ✓Specific documentation of tonsillar fossa as primary site
- ✓Laterality (right or left tonsillar fossa)
- ✓TNM staging using the appropriate staging system (AJCC 8th edition separates HPV-positive and HPV-negative oropharyngeal cancer staging)
Commonly Confused Codes
C09.1 — Tonsillar pillar; the fossa is the pocket where the tonsil sits, the pillars are the tissue folds flanking the tonsilC09.9 — Tonsil, unspecified; avoid when fossa is specifically documentedC09.8 — Overlapping sites of tonsil; use when tumor spans multiple tonsillar subsitesC10.2 — Lateral wall of oropharynx; tonsillar fossa tumors may extend to the lateral oropharyngeal wall