Merkel cell carcinoma ICD-10 Coding

Merkel cell carcinoma ICD-10 Coding

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that develops from hormone making cells in the skin. Unlike basal cell or squamous cell carcinoma, MCC will often metastasize to the lymph nodes and internal organs. The cure rate is reported at 80 percent for those cases that have not yet metastasized, and drops to 50 percent after the lesion metastasizes regionally.
MCC is commonly found on the sun-exposed areas of the head and neck. MCC is most common on fair-skinned Caucasians 60-80 years old, and is twice as common in men.
Clinical documentation for MCC should include the type of malignancy, the location of the MCC, and laterality (when indicated), as shown by the code descriptors:

C4A.0 Merkel cell carcinoma of the lip
C4A.10 …unspecified eyelid, including canthus
C4A.11 …right eyelid, including canthus
C4A.12 …left eyelid, including canthus
C4A.20 …unspecified ear and external auricular canal
C4A.21 …right ear and external auricular canal
C4A.22 …left ear and external auricular canal
C4A.30 …unspecified part of face
C4A.31 …of nose
C4A.32 …of other parts of face
C4A.4 …of scalp and neck
C4A.51 …of the anal skin
C4A.52 …of skin of breast
C4A.59 …other part of trunk
C4A.60 …of unspecified upper limb, including shoulder
C4A.61 …of right upper limb, including shoulder
C4A.62 …of left upper limb, including shoulder
C4A.70 …of unspecified lower limb, including hip
C4A.71 …of right lower limb, including hip
C4A.72 …of left lower limb, including hip
C4A.8 …of overlapping sites
C4A.9 …unspecified

As demonstrated, the fourth character in category C4A codes is specific to the location of the MCC. The codes for eyelids (C4A.1), ears and external auricular (C4A.2), and upper and lower extremities (C4A.6 and C4A.7) specify laterality (which is identified with a fifth character).
The fifth character in sub-category C4A.5 specifies the location of the trunk, with sites of anal skin, skin of the breast, and other specified parts of the trunk. C4A.8 is used for overlapping sites.

Example: A 75-year-old patient presents with a rapidly enlarging mass on the upper rim of his upper lip. He is fair skinned and lives on a farm, using no sun protection other than a baseball cap. The mass has been rapidly increasing in size for the past 2 months. After diagnostic testing he is diagnosed with Merkel cell carcinoma of the rim of the upper lip.

In this example, the patient is diagnosed with MCC of the rim of the upper lip. Code C4A.0 (MCC of the lip) is appropriate.
Finally, note that an Excludes1 note is included at C4A.0, for malignant neoplasm of the vermillion of lip (C00.0-C00.2 and C4A.5 that excludes malignant neoplasm of anus NOS (C21.0 Malignant neoplasm of anus, unspecified) and malignant neoplasm of scrotum (C63.2 Malignant neoplasm of scrotum). Excludes1 notes indicate mutually exclusive codes and represents two conditions that cannot be reported at the same encounter.

John Verhovshek
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John Verhovshek, MA, CPC, is a contributing editor at AAPC. He has been covering medical coding and billing, healthcare policy, and the business of medicine since 1999. He is an alumnus of York College of Pennsylvania and Clemson University.

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