Malignant neoplasm of tonsillar fossa

This code signifies a primary cancerous tumor originating in the tonsillar fossa, which is the depression between the palatoglossal and palatopharyngeal arches where the palatine tonsil is located. This malignancy is a type of oropharyngeal cancer.

Assign this code when documentation clearly indicates a primary malignant neoplasm specifically located in the tonsillar fossa. Supporting documentation would include pathology reports confirming malignancy and precise anatomical location, or physician notes detailing the diagnosis and site.

• Differentiate from malignancies of the tonsil itself (e.g., palatine tonsil), as these have distinct codes.
• Ensure the documentation specifies "tonsillar fossa" and not a more general oropharyngeal site.
• Sequence this code as the primary diagnosis when it is the reason for the encounter or treatment.