Malignant neoplasm of colon (C18) ICD-10-CM
The C18 code range covers malignant neoplasm of colon with 11 ICD-10-CM diagnosis codes. 10 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
- malignant carcinoid tumors of the colon C7A.02
Codes in the C18 Range 11 codes · 10 billable
- C18 Malignant neoplasm of colonNon-billable
- C18.0 Malignant neoplasm of cecum
- C18.1 Malignant neoplasm of appendix
- C18.2 Malignant neoplasm of ascending colon
- C18.3 Malignant neoplasm of hepatic flexure
- C18.4 Malignant neoplasm of transverse colon
- C18.5 Malignant neoplasm of splenic flexure
- C18.6 Malignant neoplasm of descending colon
- C18.7 Malignant neoplasm of sigmoid colon
- C18.8 Malignant neoplasm of overlapping sites of colon
- C18.9 Malignant neoplasm of colon, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the C18 range.
Appendiceal Neoplasms
Tumors or cancer of the APPENDIX.
Appendix
A worm-like blind tube extension from the CECUM.
Colon
The segment of LARGE INTESTINE between the CECUM and the RECTUM. It includes the ASCENDING COLON; the TRANSVERSE COLON; the DESCENDING COLON; and the SIGMOID COLON.
About the C18 Code Range
ICD-10 code C18 and its subcodes specifically identify different types of malignant neoplasms (cancers) of the colon. These codes are used to classify and document the precise location of colon cancer, whether it affects the cecum, appendix, ascending colon, or other parts of the colon.
The ICD-10 code for malignant neoplasm of colon helps healthcare providers distinguish cancer sites within the large intestine, which is critical for treatment planning and reporting. For instance, code C18.0 covers cancers such as "adenocarcinoma of cecum" or "primary carcinoma of cecum," while C18.1 includes malignancies of the appendix, including "primary mucinous adenocarcinoma." Similarly, other codes like C18.2 and C18.3 describe malignant tumors at the ascending colon and hepatic flexure, respectively. The term "malignant tumor of the sigmoid colon" corresponds to C18.7. If the cancer's exact location isn't specified, C18.9 represents an unspecified malignant neoplasm of the colon. These synonyms alongside their respective codes assist medical coders and healthcare professionals in selecting the most accurate code for colorectal malignancies.
Questions About This Page
How many billable codes are in the C18 range?
Of the 11 codes in this range, 10 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the C18 range classify?
The range classifies malignant neoplasm of colon. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
