C58 vs O01.9
C58 and O01.9 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 C58
hydatidiform mole NOS (O01.9)
C58
Malignant neoplasm of placenta
Billable
- Chapter 2
- Neoplasms
- Section
- C51-C58
Use when the record says
- choriocarcinoma NOS
- chorionepithelioma NOS
Indexed under
- Choriocarcinoma › unspecified site › female
- Carcinoma › chorionic › unspecified site › female (malignant)
O01.9
Hydatidiform mole, unspecified
BillableUnspecified
- Chapter 15
- Pregnancy, childbirth and the puerperium
- Section
- O00-O08
Use when the record says
- Trophoblastic disease NOS
- Vesicular mole NOS
Indexed under
- Hydatidiform mole (benign) (complicating pregnancy) (delivered) (undelivered)
- Trophoblastic disease
- Mole › hydatid, hydatidiform (pigmented)
- Pregnancy › complicated by › hydatidiform mole (single) (uterine)
- Pregnancy › molar NEC › hydatidiform (single) (uterine)
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