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  3. C00–D49
  4. C43-C44
  5. C4A
  6. 2026 ICD-10-CM Code C4A

2026 ICD-10-CM Diagnosis Code C4A

Merkel cell carcinoma

ICD-10-CM Code:
C4A
ICD-10 Code for:
Merkel cell carcinoma
Is Billable?
Not Valid for Submission
Code Navigator:

C4A is a non-specific and non-billable diagnosis code code, consider using a code with a higher level of specificity from the list below for a diagnosis of merkel cell carcinoma. The code is not specific and is NOT valid for the year 2026 for the submission of HIPAA-covered transactions. Category or Header define the heading of a category of codes that may be further subdivided by the use of 4th, 5th, 6th or 7th characters.

Specific Coding Applicable to Merkel cell carcinoma

Non-specific codes like C4A require more digits to indicate the appropriate level of specificity. Consider using any of the following billable codes with a higher level of specificity when coding for merkel cell carcinoma:

  • Use C4A.0 for Merkel cell carcinoma of lip

  • C4A.1 for Merkel cell carcinoma of eyelid, including canthus

  • Use C4A.10 for Merkel cell carcinoma of unspecified eyelid, including canthus

  • C4A.11 for Merkel cell carcinoma of right eyelid, including canthus

  • C4A.12 for Merkel cell carcinoma of left eyelid, including canthus

  • C4A.2 for Merkel cell carcinoma of ear and external auricular canal

  • Use C4A.20 for Merkel cell carcinoma of unspecified ear and external auricular canal

  • Use C4A.21 for Merkel cell carcinoma of right ear and external auricular canal

  • Use C4A.22 for Merkel cell carcinoma of left ear and external auricular canal

  • C4A.3 for Merkel cell carcinoma of other and unspecified parts of face

  • Use C4A.30 for Merkel cell carcinoma of unspecified part of face

  • Use C4A.31 for Merkel cell carcinoma of nose

  • Use C4A.39 for Merkel cell carcinoma of other parts of face

  • Use C4A.4 for Merkel cell carcinoma of scalp and neck

  • C4A.5 for Merkel cell carcinoma of trunk

  • Use C4A.51 for Merkel cell carcinoma of anal skin

  • Use C4A.52 for Merkel cell carcinoma of skin of breast

  • Use C4A.59 for Merkel cell carcinoma of other part of trunk

  • C4A.6 for Merkel cell carcinoma of upper limb, including shoulder

  • Use C4A.60 for Merkel cell carcinoma of unspecified upper limb, including shoulder

  • Use C4A.61 for Merkel cell carcinoma of right upper limb, including shoulder

  • Use C4A.62 for Merkel cell carcinoma of left upper limb, including shoulder

  • C4A.7 for Merkel cell carcinoma of lower limb, including hip

  • Use C4A.70 for Merkel cell carcinoma of unspecified lower limb, including hip

  • Use C4A.71 for Merkel cell carcinoma of right lower limb, including hip

  • Use C4A.72 for Merkel cell carcinoma of left lower limb, including hip

  • Use C4A.8 for Merkel cell carcinoma of overlapping sites

  • Use C4A.9 for Merkel cell carcinoma, unspecified

Code Classification

  • Neoplasms
    C00–D49
    • Melanoma and other malignant neoplasms of skin
      C43-C44
      • Merkel cell carcinoma
        C4A

Patient Education


Skin Cancer

Skin cancer is the most common form of cancer in the United States. The two most common types are basal cell cancer and squamous cell cancer. They usually form on the head, face, neck, hands, and arms. Another type of skin cancer, melanoma, is more dangerous but less common.

Anyone can get skin cancer, but it is more common in people who :

  • Spend a lot of time in the sun or have been sunburned
  • Have light-colored skin, hair and eyes
  • Have a family member with skin cancer
  • Are over age 50

You should have your doctor check any suspicious skin markings and any changes in the way your skin looks. Treatment is more likely to work well when cancer is found early. If not treated, some types of skin cancer cells can spread to other tissues and organs. Treatments include surgery, radiation therapy, chemotherapy, photodynamic therapy (PDT), and biologic therapy. PDT uses a drug and a type of laser light to kill cancer cells. Biologic therapy boosts your body's own ability to fight cancer.

NIH: National Cancer Institute


[Learn More in MedlinePlus]

Merkel Cell Carcinoma Treatment (PDQ®)

Learn about Merkel cell carcinoma risk factors, signs and symptoms, tests to diagnose, factors affecting prognosis, staging, and treatment.
[Learn More in MedlinePlus]

Code History

  • FY 2026 - No Change, effective from 10/1/2025 through 9/30/2026
  • FY 2025 - No Change, effective from 10/1/2024 through 9/30/2025
  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.