C4A.9 Merkel cell carcinoma, unspecified

Billable ICD-10-CM code, FY2026.

Applicable to

• Merkel cell carcinoma of unspecified site
• Merkel cell carcinoma NOS

Risk adjustment (HCC)

• CMS-HCC V28: HCC 21 — Lymphoma and Other Cancers
• CMS-HCC V22: HCC 12 — Breast, Prostate, and Other Cancers and Tumors
• RxHCC V08: HCC 22 — Prostate, Breast, Bladder, and Other Cancers and Tumors
• ESRD V24: HCC 12

MS-DRG index

Defines the logic of DRG(s) 595-596 in MDC 09.

Approximate ICD-9-CM (GEMs)

• 209.36 Merkel cell carcinoma of other sites (approximate)

Code annotations containing back-references to C4A.9

Back-references to C4A

• Type 2 Excludes: C43 Malignant melanoma of skin ("Merkel cell carcinoma (C4A.-)")
• Type 1 Excludes: C44 Other and unspecified malignant neoplasm of skin ("Merkel cell carcinoma (C4A.-)")
• Type 2 Excludes: C7A Malignant neuroendocrine tumors ("Merkel cell carcinoma (C4A.-)")

Diagnosis Index entries for C4A.9

• Carcinoma (malignant) › Merkel cell

Nearby codes

• C4A.7 Merkel cell carcinoma of lower limb, including hip
• C4A.70 Merkel cell carcinoma of unspecified lower limb, including hip
• C4A.71 Merkel cell carcinoma of right lower limb, including hip
• C4A.72 Merkel cell carcinoma of left lower limb, including hip
• C4A.8 Merkel cell carcinoma of overlapping sites
• C4A.9 Merkel cell carcinoma, unspecified (this code)