Excludes1 pair
C79.2 vs C7B.1
C79.2 and C7B.1 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
The official note, declared on C79.2
secondary Merkel cell carcinoma (C7B.1)
C7B.1
Secondary Merkel cell carcinoma
Billable
- Chapter 2
- Neoplasms
- Section
- C7B
Use when the record says
- Merkel cell carcinoma nodal presentation
- Merkel cell carcinoma visceral metastatic presentation
Indexed under
- Carcinoma › Merkel cell › nodal presentation
- Carcinoma › Merkel cell › secondary
- Carcinoma › Merkel cell › visceral metastatic
- Carcinoma › secondary › Merkel cell
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027