C04
Malignant neoplasm of floor of mouth
C04 is a non-billable ICD-10-CM code category for malignant neoplasm of floor of mouth. Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. The more specific codes under it are C04.0 Malignant neoplasm of anterior floor of mouth; C04.1 Malignant neoplasm of lateral floor of mouth; C04.8 Malignant neoplasm of overlapping sites of floor of mouth and C04.9 Malignant neoplasm of floor of mouth, unspecified. Its coding notes include a Use additional code instruction.
Guidelines tip
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
A primary malignancy code stays in use until treatment directed at that site is completed. After that, with no evidence of disease at the site, Z85 gives the former site.
Use additional code
Add the listed code as a secondary code, if known.
Notes
Also from chapter/block level (8 notes)
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).