C56.9 Malignant neoplasm of unspecified ovary

The ICD-10-CM code for Malignant neoplasm of unspecified ovary is C56.9 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

2: Neoplasms (C00-D49)

Section

C51-C58: Malignant neoplasms of female genital organs (C51-C58)

Category C56

5 codes (4 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to C56.9:

• Cancer › ovarian
• Adenocarcinoma › papillocystic › unspecified site
• Cystadenocarcinoma › papillary › unspecified site
• Carcinoma (malignant) › papillocystic › unspecified site
• Adenocarcinoma › pseudomucinous › unspecified site
• Cystadenocarcinoma › pseudomucinous › unspecified site
• Carcinoma (malignant) › pseudomucinous › unspecified site
• Cystadenocarcinoma › mucinous › unspecified site

U.S. Hospital Utilization

• An estimated 33,465 U.S. inpatient stays in 2023 included C56.9 among the documented diagnoses.
• 6,320 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Tx of primary site (TOC entry)

a. Admission/Encounter for treatment of primary site ............................................................. 33

Tx of secondary site (TOC entry)

b. Admission/Encounter for treatment of secondary site .......................................................... 33

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)