2027 ICD-10-CM Diagnosis Code C56.9Malignant neoplasm of unspecified ovary

ICD-10-CM Codes›C00–D49›C51-C58›C56

ICD-10-CM C56.9
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

C56.9 is a billable ICD-10-CM diagnosis code for malignant neoplasm of unspecified ovary. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 731 through 733, 754 through 756. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 29 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Female reproductive system cancers - ovary.

For Medicare Advantage risk adjustment, C56.9 maps to CMS-HCC Category 22 (Bladder, Colorectal, and Other Cancers) under the V28 model, adding a risk factor of about 0.363 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
C56.9
Billable Status
Yes — Valid for Submission
Code Describes
Malignant neoplasm of unspecified ovary
Short Description
Malignant neoplasm of unspecified ovary
Same as the full description in the CMS dataset.
Parent Code
C56
Malignant neoplasm of ovary

Code Classification

ChapterC00–D49Neoplasms
SectionC51-C58Malignant neoplasms of female genital organs
CategoryC56Malignant neoplasm of ovary
This CodeC56.9Malignant neoplasm of unspecified ovary

Medicare Risk Adjustment (HCC)Billing

C56.9 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 22— Bladder, Colorectal, and Other Cancers
Payment HCC · PY 2027 one of 126 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.363
community, non-dual, aged · ranges 0.314–0.410 across segments
Hierarchy
Superseded by HCC 17, HCC 18, HCC 19, HCC 20, and HCC 21
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 10
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 10 · ESRD (V21): HCC 10 · ESRD (V24): HCC 10
ESRD V21 weights: 0.136 dialysis, 0.451–0.668 functioning graft · ESRD V24 weights: 0.111 dialysis, 0.467–0.780 functioning graft
Part D (RxHCC)
RxHCC 22 — Prostate, Breast, Bladder, and Other Cancers and Tumors
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Adenocarcinoma of ovary
  • Anemia in neoplastic disease
  • Anemia in ovarian carcinoma
  • Carcinoma of ovary, stage 1
  • Carcinoma of ovary, stage 2
  • Carcinoma of ovary, stage 3
  • Carcinoma of ovary, stage 4
  • Carcinosarcoma of ovary
  • Carcinosarcoma of uterine adnexa
  • Choriocarcinoma
  • Choriocarcinoma of ovary
  • Clear cell neoplasm of ovary
  • Clear cell adenocarcinoma of Mullerian origin of ovary
  • Clear cell adenocarcinoma of ovary
  • Cystadenocarcinoma of ovary
  • Embryonal carcinoma
  • Embryonal carcinoma of ovary
  • Endometrioid carcinoma ovary
  • Epithelial ovarian tumor, FIGO stage II
  • Epithelial ovarian tumor, FIGO stage IIC
  • Familial cancer of breast
  • Familial ovarian cancer
  • FIGO ovarian tumor stage finding
  • FIGO stage finding for epithelial tumor of ovary
  • Germ cell neoplasm of ovary
  • Hereditary breast and ovarian cancer syndrome
  • High grade serous carcinoma
  • High grade serous carcinoma of intraabdominal organ
  • Invasive ovarian tumor omental implants absent
  • Invasive ovarian tumor omental implants present
  • Malignant Brenner tumor of ovary
  • Malignant dysgerminoma of ovary
  • Malignant epithelial neoplasm of ovary
  • Malignant germ cell neoplasm of ovary
  • Malignant granulosa cell tumor of ovary
  • Malignant immature teratoma of ovary
  • Malignant neoplasm involving left fallopian tube by direct extension from ovary
  • Malignant neoplasm involving right fallopian tube by direct extension from ovary
  • Malignant neoplasm involving urinary bladder by direct extension from ovary
  • Malignant neoplasm of ovary
  • Malignant non-dysgerminomatous germ cell neoplasm of ovary
  • Malignant sex cord tumor of ovary
  • Malignant teratoma
  • Malignant tumor involving an organ by direct extension from ovary
  • Malignant tumor involving left broad ligament by direct extension from ovary
  • Malignant tumor involving rectum by direct extension from ovary
  • Malignant tumor involving right broad ligament by direct extension from ovary
  • Malignant tumor involving uterine cervix by direct extension from ovary
  • Malignant tumor involving uterine corpus by direct extension from ovary
  • Malignant tumor involving vagina by direct extension from ovary
  • Malignant tumor involving vulva by direct extension from ovary
  • Mucinous cystadenocarcinoma of ovary
  • Non-invasive ovarian tumor omental implants absent
  • Non-invasive ovarian tumor omental implants present
  • Polyembryoma
  • Primary carcinosarcoma of ovary
  • Primary carcinosarcoma of uterine adnexa
  • Primary clear cell adenocarcinoma of ovary
  • Primary cystadenocarcinoma of ovary
  • Primary endometrioid carcinoma of ovary
  • Primary high grade serous adenocarcinoma of ovary
  • Primary low grade serous adenocarcinoma of ovary
  • Primary malignant dysgerminoma of ovary
  • Primary malignant granulosa cell tumor of ovary
  • Primary malignant neoplasm of ovary
  • Primary malignant Sertoli-Leydig cell tumor of ovary
  • Primary malignant sex cord tumor of ovary
  • Primary mucinous adenocarcinoma of ovary
  • Primary mucinous carcinoma of uterine adnexa
  • Primary mucinous cystadenocarcinoma of ovary
  • Primary non-gestational choriocarcinoma of ovary
  • Primary serous carcinoma of uterine adnexa
  • Primary serous papillary cystadenocarcinoma ovary
  • Primary small cell neuroendocrine carcinoma of ovary
  • Primary theca steroid producing cell malignant neoplasm of ovary
  • Primary undifferentiated carcinoma of ovary
  • Recurrent ovarian cancer
  • Sarcoma of ovary
  • Serous cystadenoma borderline malignancy of ovary
  • Serous papillary cystadenocarcinoma ovary
  • Small cell carcinoma of ovary
  • Teratoma of ovary
  • Theca steroid producing cell malignant neoplasm of ovary
  • Undifferentiated carcinoma of ovary
  • Yolk sac tumor
  • Yolk sac tumor of ovary

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to C56.9: its own notes plus those printed at C56, block C51-C58, and Chapter 2. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block C51-C58 Malignant neoplasms of female genital organs applies to 36 codes
  • malignant neoplasm of skin of female genital organs

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From C56 Malignant neoplasm of ovary applies to 4 codes
  • code to identify any functional activity

Notes

General instructions on how these codes are used.

From Chapter 2 (C00-D49) Neoplasms applies to 1,730 codes
  • Functional activity
  • All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
  • Morphology [Histology]
  • Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
  • Primary malignant neoplasms overlapping site boundaries
  • A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
  • Malignant neoplasm of ectopic tissue
  • Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name C56.9, its category, or a range that includes it.

Applicable To 2

These notes mention C56.9.

  • Z80.4 Family history of malignant neoplasm of genital organs
    Conditions classifiable to C51-C63 names C51-C63, which includes this code
  • Z85.4 Personal history of malignant neoplasm of genital organs
    Conditions classifiable to C51-C63 names C51-C63, which includes this code

Excludes1 1

These codes carry an Excludes1 note naming C56.9: they are not reported together with it, unless the two conditions are unrelated.

  • C75 Malignant neoplasm of other endocrine glands and related structures
    malignant neoplasm of ovary (C56.-) names C56.-, which includes this code

Code First 2

These codes say to code first a condition named in the note, and C56.9 is one of the conditions named.

  • R18.0 Malignant ascites
    malignant neoplasm of ovary (C56.-) names C56.-, which includes this code
  • Z17 Estrogen, and other hormones and factors receptor status
    malignant neoplasm of ovary (C56.-) names C56.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

  • Cancer See Also: Neoplasm, by site, malignant;

    • ovarian See Also: Neoplasm ovary, malignant; C56.9

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO033
Female reproductive system cancers - ovary
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Malignant Ovarian Neoplasm

    a primary or metastatic malignant neoplasm involving the ovary. most primary malignant ovarian neoplasms are either carcinomas (serous, mucinous, or endometrioid adenocarcinomas) or malignant germ cell tumors. metastatic malignant neoplasms to the ovary include carcinomas, lymphomas, and melanomas.

Patient EducationClinical

Ovarian Cancer

Cancer is a disease in which abnormal cells in the body grow out of control and form a tumor. Ovarian cancer is a cancerous tumor that forms in the tissues of an ovary. The ovaries are a pair of female reproductive glands that make eggs and female hormones.

The full article covers:

  • What is ovarian cancer?
  • What are the types of ovarian cancer?
  • What causes ovarian cancer?
  • Who is more likely to develop ovarian cancer?
  • What are the symptoms of ovarian cancer?
  • How is ovarian cancer diagnosed?
  • What are the treatments for ovarian cancer?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C56.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
183.0 Malign neopl ovary
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About C56.9Overview

What is the ICD-10 code for malignant neoplasm of unspecified ovary?

The ICD-10-CM code for malignant neoplasm of unspecified ovary is C56.9 (sometimes written as C569). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is C56.9 (Malignant neoplasm of ovary) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of unspecified ovary on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does C56.9 group to?

When malignant neoplasm of unspecified ovary is the principal diagnosis on an inpatient stay, it groups to MS-DRG 732, 755, 756, 754, 733, 731, with relative weights from 0.8583 to 3.5462 depending on complications. Higher weights mean higher Medicare reimbursement.

Is C56.9 a CC or MCC?

CMS lists C56.9 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 29 closely related codes in its exclusion list.

Does C56.9 need an additional code?

When the condition applies, yes. The Use Additional Code note at C56, which applies to C56.9, reads: code to identify any functional activity. The additional code is reported after C56.9.

What HCC is C56.9?

C56.9 (malignant neoplasm of unspecified ovary) maps to CMS-HCC Category 22 (Bladder, Colorectal, and Other Cancers), commonly written as HCC 22, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 10 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 22.

Does C56.9 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, C56.9 adds a risk adjustment factor of about 0.363 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.314 to 0.410 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, HCC 20, and HCC 21) supersedes it when both are reported. See the full factor table on the HCC 22 category page.