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ICD-10 Codes for MCC

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ICD-10 stands for International Classification of Diseases, version 10. These codes provide a numbering system to allow all diseases to be characterized by sub-types. Merkel cell carcinoma (MCC) is a neuroendocrine skin cancer with a higher propensity for recurrence and metastasis than melanoma or squamous cell carcinoma. Despite aggressive behavior and the tripling of its reported incidence in the past 20 years, there is extensive confusion about how MCC should be managed. Worldwide adoption in 2009 of specific ICD diagnostic codes for MCC improved the understanding and management of this often-lethal skin cancer.


Until late 2009, MCC was coded in the ICD system as 173.x: “Other malignant neoplasm of skin” along with BCC, SCC and many other skin cancers. This often impeded management of MCC patients as insurance companies use these codes to determine whether or not a test, scan or treatment is appropriate for the diagnosis in question. When a disease does not have a code that appropriately captures its management and treatment, multiple codes must be used to attempt to justify proposed therapies for insurance and billing approvals. This was certainly the case for MCC as it was grouped with BCC and other benign diagnoses that rarely require aggressive management or inpatient care.

To address this issue, a petition was made to the CDC on behalf of the Merkel cell carcinoma Multi-center Interest Group (MMIG) to create specific ICD codes for MCC. The rationale for this petition included the fact that other distinctive skin cancers with potentially aggressive behavior have unique codes. These include cutaneous T cell lymphoma (CTCL) the incidence of which is approximately that of MCC (code 202.x) as well as malignant melanoma (172.x). In January 2009, the CDC granted 7 MCC-specific codes that became active as of October 1, 2009. The introduction of these specific codes, later followed by the updated ICD-10 codes (see table) help MCC patients in obtaining insurance approval for the appropriate treatment, help track MCC-associated costs and aid researchers in identifying and following MCC patients.

ICD-10 Code

Merkel Cell Carcinoma Description

C4A MCC unspecified
MCC of the Face
C4A.0 Lip
C4A.1 Eyelid (including canthus)
C4A.10 Eyelid, unspecified
C4A.11 Eyelid, right
C4A.12 Eyelid, left
C4A.2 Ear (and external auricular canal)
C4A.20 Ear, unspecified
C4A.21 Ear, right
C4A.22 Ear, left
C4A.3 Face, unspecified
C4A.30 Face, other part
C4A.31 Nose
C4A.4 Scalp and Neck
MCC of the Limb
C4A.6 Upper limb (including shoulder)
C4A.60 Upper limb, unspecified
C4A.61 Upper limb, right
C4A.62 Upper limb, left
C4A.7 Lower limb (including hip)
C4A.70 Lower limb, unspecified
C4A.71 Lower limb, right
C4A.72 Lower limb, left
MCC of the Trunk
C4A.5 Trunk, unspecified
C4A.51 Anal or perianal skin
C4A.52 Skin of breast
C4A.59 Trunk, other part
Other MCC
C4A.8 Overlapping sites (eg, junction of neck and trunk)
Metastatic MCC
C7B.1 Metastatic MCC or nodal presentation without known primary
C4A.9 unspecified site
History of MCC
Z85.821 History of MCC of the skin


Read the ICD codes section on the FAQ page for answers to frequently asked questions about the MCC ICD codes.