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ICD-10-CM C20: Malignant neoplasm of rectum

C20 is the billable ICD-10-CM code for malignant neoplasm of rectum, in category C20 (Malignant neoplasm of rectum) of the Malignant neoplasms of digestive organs section. As a principal diagnosis it groups to MS-DRG 374 Digestive Malignancy with MCC, MS-DRG 375 Digestive Malignancy with CC, MS-DRG 376 Digestive Malignancy without CC/MCC (MDC 06 MDC 06: Diseases and Disorders of the Digestive System). It maps to HCC 22 (Bladder, Colorectal, and Other Cancers) in CMS-HCC V28. As a secondary diagnosis it is a CC, excluded with 22 principal diagnoses. 74 LCD billing and coding articles list it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
C20
billable FY2027 ICD-10-CM code
Category
C20 Malignant neoplasm of rectum
Chapter
2: Neoplasms (C00-D49)
CC/MCC (MS-DRG v44)
CC
CMS-HCC V28
HCC 22
POA reporting
Required

Tabular list notes for C20

Inclusion terms
  • Malignant neoplasm of rectal ampulla
Excludes1 (never coded together)
  • malignant carcinoid tumor of the rectum (C7A.026)

MS-DRG grouping when C20 is the principal diagnosis

MS-DRG v44 groups for C20 as principal diagnosis
MDCMS-DRGs
06 MDC 06: Diseases and Disorders of the Digestive System374375376

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for C20 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, C20 is a CC under MS-DRG v44, unless the principal diagnosis is one of the 22 codes in its exclusion list. Check C20 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.

CMS-HCC V28 risk adjustment

In the PY2027 mapping, C20 maps to HCC 22 (Bladder, Colorectal, and Other Cancers). The HCC lookup shows the RAF weight and the hierarchy.

LCD billing and coding articles that list C20

74 current Medicare billing and coding articles list C20 among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM C20 mean?

C20 means malignant neoplasm of rectum. The tabular list also files these terms under it: Malignant neoplasm of rectal ampulla. It is one of 1 billable codes under C20, malignant neoplasm of rectum.

What can't be coded with C20?

Excludes1 at C20: malignant carcinoid tumor of the rectum (C7A.026). These are never reported together with C20.

Which MS-DRG does C20 group to?

As the principal diagnosis, C20 groups to MS-DRG 374 Digestive Malignancy with MCC, MS-DRG 375 Digestive Malignancy with CC, MS-DRG 376 Digestive Malignancy without CC/MCC (MDC 06 MDC 06: Diseases and Disorders of the Digestive System) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Does C20 map to an HCC?

Yes: HCC 22, Bladder, Colorectal, and Other Cancers, in the PY2027 CMS-HCC V28 mapping.

Is C20 a CC or MCC?

C20 is a CC under MS-DRG v44; 22 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.