2027 ICD-10-CM Diagnosis Code C18Malignant neoplasm of colon

ICD-10-CM Codes›C00–D49›C15-C26›C18

ICD-10-CM C18
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

C18 is a non-billable ICD-10-CM category code for malignant neoplasm of colon, so it cannot be submitted on claims. Use a more specific code from this category instead, such as C18.0, C18.1, C18.2, and C18.3.

Code Identity

ICD-10-CM Code
C18
Billable Status
No — Non-Billable Category
Code Describes
Malignant neoplasm of colon
Short Description
Malignant neoplasm of colon
Same as the full description in the CMS dataset.
Chapter
C15-C26
Malignant neoplasms of digestive organs

Code Classification

ChapterC00–D49Neoplasms
SectionC15-C26Malignant neoplasms of digestive organs
CategoryC18Malignant neoplasm of colon
This CodeC18Malignant neoplasm of colon

Specific Coding for Malignant neoplasm of colonOverview

Non-specific codes like C18 require more characters. Use one of these billable codes instead:

  • Use C18.0 for Malignant neoplasm of cecum

  • Use C18.1 for Malignant neoplasm of appendix

  • Use C18.2 for Malignant neoplasm of ascending colon

  • Use C18.3 for Malignant neoplasm of hepatic flexure

  • Use C18.4 for Malignant neoplasm of transverse colon

  • Use C18.5 for Malignant neoplasm of splenic flexure

  • Use C18.6 for Malignant neoplasm of descending colon

  • Use C18.7 for Malignant neoplasm of sigmoid colon

  • Use C18.8 for Malignant neoplasm of overlapping sites of colon

  • Use C18.9 for Malignant neoplasm of colon, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to C18: its own notes plus those printed at block C15-C26 and Chapter 2. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

On C18 itself
  • malignant carcinoid tumors of the colon (C7A.02-)
From Block C15-C26 Malignant neoplasms of digestive organs applies to 60 codes
  • Kaposi's sarcoma of gastrointestinal sites (C46.4)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block C15-C26 Malignant neoplasms of digestive organs applies to 60 codes
  • gastrointestinal stromal tumors (C49.A-)

Notes

General instructions on how these codes are used.

From Chapter 2 (C00-D49) Neoplasms applies to 1,730 codes
  • 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).

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name C18, its category, or a range that includes it.

Applicable To 2

These notes mention C18.

  • Z85.038 Personal history of other malignant neoplasm of large intestine
    Conditions classifiable to C18
  • Z80.0 Family history of malignant neoplasm of digestive organs
    Conditions classifiable to C15-C26 names C15-C26, which includes this code

Code Also 1

These codes say C18 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • D13.91 Familial adenomatous polyposis
    malignant neoplasm of colon (C18.-)

Clinical InformationClinical

  • Malignant Colon Neoplasm

    a primary or metastatic malignant neoplasm that affects the colon. representative examples include carcinoma, lymphoma, and sarcoma.

Patient EducationClinical

Colorectal Cancer

Colorectal cancer is cancer that develops in the tissues of the colon or rectum. Your colon and rectum are part of your digestive system:

The full article covers:

  • What is colorectal cancer?
  • What causes colorectal cancer?
  • Who is more likely to develop colorectal cancer?
  • What are the symptoms of colorectal cancer?
  • What is screening for colorectal cancer and who needs it?
  • How is colorectal cancer diagnosed?
  • What are the treatments for colorectal cancer?
  • Can colorectal cancer be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About C18Overview

What is the ICD-10 code for malignant neoplasm of colon?

C18 is the ICD-10-CM category for malignant neoplasm of colon, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is C18 (Malignant neoplasm of colon) a billable code?

No. This is a category header that groups the codes for malignant neoplasm of colon, and headers cannot be submitted on claims. Claims for malignant neoplasm of colon need a more specific code from this category, such as C18.0, C18.1, and C18.2.

Can C18 be reported with a code from C7A.02?

Not as a rule. The Excludes1 note on C18 lists "malignant carcinoid tumors of the colon (C7A.02-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).