Malignant neoplasm of overlapping sites of floor of mouth

This code signifies a primary cancerous growth that spans across multiple distinct anatomical sub-sites within the floor of the mouth, making it impossible to assign to a single, specific sub-site. This includes malignancies that originate in one area but extend significantly into adjacent areas of the floor of the mouth.

Use this code when documentation clearly indicates a malignant neoplasm affecting contiguous or overlapping regions of the floor of the mouth, such as involvement of both the anterior and lateral floor. This code is appropriate when the tumor's extent prevents precise localization to a single C04.0, C04.1, or C04.2 subcategory.

• Ensure the physician's documentation explicitly states "overlapping sites" or describes involvement of multiple, non-discrete sub-sites of the floor of the mouth.
• Do not use this code if the primary site can be clearly identified as a single sub-site (e.g., anterior floor of mouth).
• Always sequence this code as the primary diagnosis if it represents the reason for the encounter, followed by any applicable codes for metastatic disease.