C4A.31 ICD-10-CM Code: Merkel cell carcinoma of nose
Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.
Inpatient Payment Groups (MS-DRG)
MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43.0 (FY2026), Appendix B.
- MS-DRG 595 — MAJOR SKIN DISORDERS WITH MCC (MDC 09)
- MS-DRG 596 — MAJOR SKIN DISORDERS WITHOUT MCC (MDC 09)
A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.
Risk Adjustment (CMS-HCC)
Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.
- HCC 21 — Lymphoma and Other Cancers (supersedes HCC 22, HCC 23)
Other models: CMS-HCC V22 HCC 12 · RxHCC V08 HCC 22
Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.
Official Registry Overview & Definition
Nearest Codes in This Family
Official ICD-10-CM classifications closest to C4A.31 in its code family, with their registry titles.
- C4A.20 — Merkel cell carcinoma of unspecified ear and external auricular canal
- C4A.21 — Merkel cell carcinoma of right ear and external auricular canal
- C4A.22 — Merkel cell carcinoma of left ear and external auricular canal
- C4A.3 — Merkel cell carcinoma of other and unspecified parts of face
- C4A.30 — Merkel cell carcinoma of unspecified part of face
- C4A.39 — Merkel cell carcinoma of other parts of face
- C4A.4 — Merkel cell carcinoma of scalp and neck
- C4A.5 — Merkel cell carcinoma of trunk
- C4A.51 — Merkel cell carcinoma of anal skin
- C4A.52 — Merkel cell carcinoma of skin of breast
Indexed Clinical Terms (1)
Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code.
- Carcinoma (malignant), Merkel cell, nose