Skip to content
Dx

ICD-10-CM 2027 diagnosis code

C18Malignant neoplasm of colon

Not billable — use a more specific code

C18 is a header code, so it can't be reported by itself. Choose one of the 10 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About C18

C18 is the ICD-10-CM diagnosis code for malignant neoplasm of colon. It belongs to block C15-C26 (malignant neoplasms of digestive organs) and chapter 2 (neoplasms). It is a header code, so it can't be reported by itself; one of its 10 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: C18.0 (cecum), C18.1 (appendix), C18.2 (colon), C18.3 (flexure), C18.4 (colon), C18.5 (flexure), C18.6 (colon), C18.7 (colon) and 2 more.

Don't report C18 together with the conditions in its Excludes1 note: malignant carcinoid tumors of the colon (C7A.02-).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under C18

Coding notes

Excludes1Not coded here — never report together with this code
  • malignant carcinoid tumors of the colon (C7A.02-)

Notes that apply from higher levels

Instructions written at a parent level also apply to C18.

Broader instructions also apply from C15-C26 Malignant neoplasms of digestive organs and Chapter 2: Neoplasms.

Codes whose notes reference C18

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about C18

Is C18 billable?

No. C18 is a header code. Report one of its more specific subcodes instead.