2022 ICD-10-CM Diagnosis Code C4A

Merkel cell carcinoma

    2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
  • C4A should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.
  • The 2022 edition of ICD-10-CM C4A became effective on October 1, 2021.
  • This is the American ICD-10-CM version of C4A - other international versions of ICD-10 C4A may differ.
The following code(s) above C4A contain annotation back-references
Annotation Back-References
In this context, annotation back-references refer to codes that contain:
  • Applicable To annotations, or
  • Code Also annotations, or
  • Code First annotations, or
  • Excludes1 annotations, or
  • Excludes2 annotations, or
  • Includes annotations, or
  • Note annotations, or
  • Use Additional annotations
that may be applicable to C4A:
  • C00-D49
    2022 ICD-10-CM Range C00-D49

    Neoplasms

    Note
    • Functional activity
    • All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
    • Morphology [Histology]
    • Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
    • Primary malignant neoplasms overlapping site boundaries
    • A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
    • Malignant neoplasm of ectopic tissue
    • Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
    Neoplasms
Clinical Information
  • A carcinoma arising from merkel cells located in the basal layer of the epidermis and occurring most commonly as a primary neuroendocrine carcinoma of the skin. Merkel cells are tactile cells of neuroectodermal origin and histologically show neurosecretory granules. The skin of the head and neck are a common site of merkel cell carcinoma, occurring generally in elderly patients. (holland et al., cancer medicine, 3d ed, p1245)
  • A rare malignant cutaneous tumor seen in elderly patients. Its usual location is on the head, neck and extremities. The tumor is composed of small round cells with scanty cytoplasm arranged in a trabecular pattern, or in ill-defined nodules or in a diffuse pattern. The tumor cells contain cytoplasmic membrane-bound dense core granules resembling neurosecretory granules.
  • A rare type of cancer that forms on or just beneath the skin, usually in parts of the body that have been exposed to the sun. It is most common in older people and in people with weakened immune systems.
Code History
  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change
  • 2021 (effective 10/1/2020): No change
  • 2022 (effective 10/1/2021): No change
Code annotations containing back-references to C4A:
  • Type 1 Excludes: C44
    ICD-10-CM Diagnosis Code C44

    Other and unspecified malignant neoplasm of skin

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Includes
    • malignant neoplasm of sebaceous glands
    • malignant neoplasm of sweat glands
    Type 1 Excludes
    • Kaposi's sarcoma of skin (C46.0)
    • malignant melanoma of skin (C43.-)
    • malignant neoplasm of skin of genital organs (C51-C52, C60.-, C63.2)
    • Merkel cell carcinoma (C4A.-)
  • Type 2 Excludes: C43
    , C7A
    ICD-10-CM Diagnosis Code C43

    Malignant melanoma of skin

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 1 Excludes
    Type 2 Excludes
    • malignant melanoma of skin of genital organs (C51-C52, C60.-, C63.-)
    • Merkel cell carcinoma (C4A.-)
    • sites other than skin-code to malignant neoplasm of the site
    ICD-10-CM Diagnosis Code C7A

    Malignant neuroendocrine tumors

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Code Also
    • any associated multiple endocrine neoplasia [MEN] syndromes (E31.2-)
    Type 2 Excludes
    • malignant pancreatic islet cell tumors (C25.4)
    • Merkel cell carcinoma (C4A.-)
    Use Additional
    • code to identify any associated endocrine syndrome, such as:
    • carcinoid syndrome (E34.0)
  • Applicable To: Z85.821
    ICD-10-CM Diagnosis Code Z85.821

    Personal history of Merkel cell carcinoma

      2016 2017 2018 2019 2020 2021 2022 Billable/Specific Code POA Exempt
    Applicable To
    • Conditions classifiable to C4A
ICD-10-CM Codes Adjacent To C4A
C43.6 Malignant melanoma of upper limb, including shoulder
C43.60 Malignant melanoma of unspecified upper limb, including shoulder
C43.61 Malignant melanoma of right upper limb, including shoulder
C43.62 Malignant melanoma of left upper limb, including shoulder
C43.7 Malignant melanoma of lower limb, including hip
C43.70 Malignant melanoma of unspecified lower limb, including hip
C43.71 Malignant melanoma of right lower limb, including hip
C43.72 Malignant melanoma of left lower limb, including hip
C43.8 Malignant melanoma of overlapping sites of skin
C43.9 Malignant melanoma of skin, unspecified
C4A Merkel cell carcinoma
C4A.0 Merkel cell carcinoma of lip
C4A.1 Merkel cell carcinoma of eyelid, including canthus
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
C4A.122 Merkel cell carcinoma of left lower eyelid, including canthus
C4A.2 Merkel cell carcinoma of ear and external auricular canal

Reimbursement claims with a date of service on or after October 1, 2015 require the use of ICD-10-CM codes.