FY2027
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Excludes1 pair

C58 vs O01.9

C58 and O01.9 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 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
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 (benign) (complicating pregnancy) (delivered) (undelivered)
  • Pregnancy › complicated by › hydatidiform mole
  • Pregnancy › molar NEC › hydatidiform

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