D22 vs I78.1
D22 and I78.1 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on I78.1
nevus NOS (D22.-)
D22
Melanocytic nevi
Not billable
- Chapter 2
- Neoplasms
- Section
- D10-D36
Use when the record says
- atypical nevus
- blue hairy pigmented nevus
- nevus NOS
I78.1
Nevus, non-neoplastic
Billable
- Chapter 9
- Diseases of the circulatory system
- Section
- I70-I79
Use when the record says
- Araneus nevus
- Senile nevus
- Spider nevus
- Stellar nevus
Indexed under
- Telangiectasia, telangiectasis (verrucous)
- Angioma › capillary
- Angioma › senile
- Angioma › spider
- Angioma › stellate
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
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