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    v1.0.28
    OpenPayerBilling CodesMelanoma and other malignant neoplasms of skinICD-10-CM c4a-merkel-cell-carcinoma
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    ICD-10-CM Code For Merkel Cell Carcinoma: Group Overview

    The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group C4A includes malignant neoplasms of Merkel cells and related primary cutaneous neuroendocrine carcinomas that primarily affect the skin. These ICD-10-CM diagnosis codes are used to document tumor site, extent, and metastatic status, capturing disease severity and anatomic involvement for Merkel cell carcinoma. Accurate coding within the ICD-10-CM C4A group supports proper claim adjudication, complete clinical documentation, and appropriate reimbursement.

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    ICD-10-CM C4A: Merkel Cell Carcinoma Overview

    The ICD-10-CM C4A group represents malignant neoplasms of Merkel cells, an aggressive primary skin cancer. These codes target dermatologic oncology and document tumor location, extent, and behavior in the integumentary system. Precise coding matters because it impacts clinical records, treatment planning, and accurate reimbursement for oncology services.

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    When to Use

    Use a code from this group when clinical documentation confirms a diagnosis of Merkel cell carcinoma or primary cutaneous neuroendocrine carcinoma. Select the specific code that reflects the documented tumor site, extent of disease, and any metastatic involvement.

    ICD-10-CM Codes

    24 rows

    ICD-10-CM CodeDescription
    C4A.0Merkel cell carcinoma of lip
    C4A.10Merkel cell carcinoma of unspecified eyelid, including canthus
    C4A.111Merkel cell carcinoma of right upper eyelid, including canthus
    C4A.112Merkel cell carcinoma of right lower eyelid, including canthus
    C4A.121Merkel cell carcinoma of left upper eyelid, including canthus
    C4A.122Merkel cell carcinoma of left lower eyelid, including canthus
    C4A.20Merkel cell carcinoma of unspecified ear and external auricular canal
    C4A.21Merkel cell carcinoma of right ear and external auricular canal
    C4A.22Merkel cell carcinoma of left ear and external auricular canal
    C4A.30Merkel cell carcinoma of unspecified part of face
    C4A.31Merkel cell carcinoma of nose
    C4A.39Merkel cell carcinoma of other parts of face
    C4A.4Merkel cell carcinoma of scalp and neck
    C4A.51Merkel cell carcinoma of anal skin
    C4A.52Merkel cell carcinoma of skin of breast
    C4A.59Merkel cell carcinoma of other part of trunk
    C4A.60Merkel cell carcinoma of unspecified upper limb, including shoulder
    C4A.61Merkel cell carcinoma of right upper limb, including shoulder
    C4A.62Merkel cell carcinoma of left upper limb, including shoulder
    C4A.70Merkel cell carcinoma of unspecified lower limb, including hip

    Showing 1–20 of 24

    DRG Codes

    2 rows

    DRG CodeDescription
    595Major Skin Disorders with MCC
    596Major Skin Disorders without MCC

    Typical Clinical Scenarios

    • Older adult with a rapidly enlarging, painless, firm, violaceous nodule on the forearm noticed over several weeks; patient presents to dermatology for biopsy of a suspicious cutaneous lesion after primary care referral. Pathology confirms primary Merkel cell carcinoma localized to the skin without regional nodal or distant metastasis; a localized primary site code from the group is assigned to document the confirmed cutaneous malignancy. Typical codes: C4A.10, C4A.111
    • Middle-aged patient with known Merkel cell carcinoma of the scalp who now presents with new palpable ipsilateral cervical lymphadenopathy and is referred for staging and management; fine-needle aspiration and imaging demonstrate metastatic involvement of regional lymph nodes. Because the skin primary has spread to regional lymph nodes, a code indicating Merkel cell carcinoma with regional lymph node metastasis is assigned to capture the site and extent of disease for staging and treatment planning. Typical codes: C4A.21, C4A.22
    • Elderly patient with history of treated Merkel cell carcinoma of the lower leg who is admitted to the hospital with acute respiratory symptoms and imaging reveals multiple pulmonary nodules consistent with metastatic disease; oncology documents distant (nonregional) metastases from the cutaneous primary. A code for Merkel cell carcinoma with distant metastasis is assigned to reflect metastatic progression and guide systemic therapy decisions. Typical codes: C4A.31, C4A.39

    Related Codes

    C43-MALIGNANT-MELANOMA-OF-SKIN

    ICD-10-CM Code For Malignant Melanoma Of Skin: Group Overview

    C44-OTHER-AND-UNSPECIFIED-SKIN-MALIGNANCY

    ICD-10-CM Code For Other And Unspecified Malignant Neoplasm Of Skin: Group Overview

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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