Malignant neoplasm of accessory sinuses (C31)

The ICD-10 code C31 series is used to classify malignant tumors found in the accessory sinuses, which are air-filled spaces around the nose. These codes specify cancers located in particular sinuses such as maxillary, ethmoidal, frontal, and sphenoid sinuses, or cases where multiple sites are involved or unspecified.

The ICD-10 code for malignant neoplasm of accessory sinuses includes several detailed subcodes. For example, C31.0 identifies cancers in the maxillary sinus, often referred to by synonyms like adenocarcinoma or squamous cell carcinoma of the maxillary sinus. Similarly, C31.1 covers malignant tumors of the ethmoidal sinus, with terms such as carcinoma of ethmoidal sinus used interchangeably. Codes C31.2 and C31.3 refer to frontal and sphenoid sinus cancers, respectively. When tumors affect multiple accessory sinuses, C31.8 is applied, and C31.9 is used when the exact sinus site is unspecified. Recognizing these synonyms helps medical coders accurately match commonly used cancer names to the precise ICD-10 code, ensuring correct documentation and treatment planning.