C4A.121 Merkel cell carcinoma of left upper eyelid, including canthus

Billable ICD-10-CM code, FY2026.

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.

Code annotations containing back-references to C4A.121

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.-)")

Nearby codes

• C4A.10 Merkel cell carcinoma of unspecified eyelid, including canthus
• C4A.11 Merkel cell carcinoma of right eyelid, including canthus
• C4A.111 Merkel cell carcinoma of right upper eyelid, including canthus
• C4A.112 Merkel cell carcinoma of right lower eyelid, including canthus
• C4A.12 Merkel cell carcinoma of left eyelid, including canthus
• C4A.121 Merkel cell carcinoma of left upper eyelid, including canthus (this code)
• C4A.122 Merkel cell carcinoma of left lower eyelid, including canthus
• C4A.2 Merkel cell carcinoma of ear and external auricular canal
• 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