C4A.62
BillableMerkel cell carcinoma of left upper limb, including shoulder
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C4A.62 an HCC code?
Yes. C4A.62 maps to Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model (and Breast, Prostate, and Other Cancers and Tumors under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for C4A.62
For C4A.62to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C4A.62 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C4A.62 is the ICD-10-CM diagnosis code for merkel cell carcinoma of left upper limb, including shoulder. A rare aggressive skin cancer (Merkel cell carcinoma) that develops on the left arm or shoulder area, including the upper limb. C4A.62 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering melanoma and other malignant neoplasms of skin (c43-c44).
Under the CMS-HCC V28 risk adjustment model, C4A.62 maps to Lymphoma and Other Cancers (HCC 21) with a community, non-dual, aged base RAF weight of 0.671. Under the older CMS-HCC V24 model, C4A.62 maps to Breast, Prostate, and Other Cancers and Tumors (HCC 12) with a community, non-dual, aged base RAF weight of 0.150. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
The '6' in the code indicates upper limb location; the '2' specifies left side. Because C4A.62 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C4A.62 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The '6' in the code indicates upper limb location; the '2' specifies left side
- •Ensure laterality is clearly documented in the medical record to support correct code selection
Clinical Significance
Merkel cell carcinoma of the left upper limb, including shoulder is a rare aggressive neuroendocrine skin cancer. Upper extremity Merkel cell carcinoma has access to axillary lymphatic drainage, making sentinel lymph node biopsy of axillary nodes critical for staging. Sun exposure on the forearms and dorsal hands increases risk in this anatomical region.
Documentation Requirements
- ✓Histopathologic confirmation of Merkel cell carcinoma with immunohistochemistry
- ✓Laterality documented as left
- ✓Specific upper limb subsite (shoulder, upper arm, forearm, wrist, hand, fingers)
- ✓Tumor dimensions and depth
- ✓Axillary sentinel lymph node biopsy status and results
- ✓Staging and treatment plan documentation
Commonly Confused Codes
- •C4A.61 — Merkel cell carcinoma of right upper limb; laterality reversed
- •C4A.60 — Merkel cell carcinoma of unspecified upper limb; use only when laterality is not documented
- •C44.621 — Other malignant neoplasm of left upper limb skin; for non-Merkel cell skin cancers
- •C43.62 — Melanoma of left upper limb including shoulder; different histology
- •C4A.59 — Merkel cell carcinoma of other trunk; shoulder area overlaps with trunk