What is ICD-10 code C58?

C58 is the ICD-10-CM diagnosis code for Malignant neoplasm of placenta. This is a rare cancer that develops in the placenta, the organ that nourishes a baby during pregnancy. It typically occurs during or shortly after pregnancy and requires immediate medical attention. C58 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C58 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C58 is a payment HCC under the CMS risk adjustment model. Under the CMS-HCC V28 risk adjustment model it maps to Bladder, Colorectal, and Other Cancers with a community, non-dual, aged base RAF weight of 0.363. Under the older CMS-HCC V24 model it maps to Lymphoma and Other Cancers at RAF 0.675. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. HCC Buddy maintains the V28 and V24 mapping, RAF weight, and MEAT documentation criteria for C58 sourced directly from the CMS-HCC model files.

Yes. C58 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C58 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for C58?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C58, V28 maps to Bladder, Colorectal, and Other Cancers at RAF 0.363 while V24 mapped to Lymphoma and Other Cancers at RAF 0.675. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting C58?

This code is rarely used in clinical practice as placental cancers are extremely uncommon; verify documentation carefully and ensure the diagnosis is clearly stated by the physician When coding this diagnosis, always include the trimester of pregnancy (O09.0-) or postpartum status codes if applicable, as this is a pregnancy-related malignancy Because C58 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

C58: Malignant neoplasm of placenta — ICD-10 | Bladder, Colorectal, and Other Cancers, Lymphoma

ICD-10-CM Code View

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Code lookupC58Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of female genital organs (C51-C58)

C58

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of placenta

This is a rare cancer that develops in the placenta, the organ that nourishes a baby during pregnancy. It typically occurs during or shortly after pregnancy and requires immediate medical attention.

Buddy Insight

Malignant neoplasm of the placenta encompasses choriocarcinoma and other gestational trophoblastic neoplasias that arise from placental tissue.

CMS-HCC V28

Mapped

HCC 22

Bladder, Colorectal, and Othe...

RAF 0.363

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Mapped

HCC 11

HHS-HCC 11

Varies by metal level

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.111

RXHCC

Mapped

HCC 22

Cancer, Other Specified Sites

RAF 0.124

Code Book Path

Official

C5Malignant neoplasms of female genital organs (C51-C58)

C58Malignant neoplasm of placenta

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C58 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C58 in this effective period.

Related Child Codes

Official

ICD-10-CM does not list child codes under C58 for this display context.

Includes

Official

choriocarcinoma NOS
chorionepithelioma NOS

Excludes 1

Official

chorioadenoma (destruens) (D39.2)
hydatidiform mole NOS (O01.9)
invasive hydatidiform mole (D39.2)
male choriocarcinoma NOS (C62.9-)
malignant hydatidiform mole (D39.2)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C58 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C58 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C58 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Pathologic confirmation of placental malignancy (choriocarcinoma, invasive mole, or placental site trophoblastic tumor)

Beta-hCG levels and trend

Staging (FIGO staging system for gestational trophoblastic neoplasia)

Relationship to most recent pregnancy (molar pregnancy, normal pregnancy, ectopic, or abortion)

MEAT Support

HCC Buddy guidance

Pathologic confirmation of placental malignancy (choriocarcinoma, invasive mole, or placental site trophoblastic tumor)

Beta-hCG levels and trend

Staging (FIGO staging system for gestational trophoblastic neoplasia)

Relationship to most recent pregnancy (molar pregnancy, normal pregnancy, ectopic, or abortion)

Audit Caution

HCC Buddy guidance

Coding a hydatidiform mole (benign or premalignant) as C58 — molar pregnancies use O01 codes until malignancy is confirmed

Failing to include pregnancy-related codes (O09 series or postpartum codes) when applicable

Not recognizing that gestational trophoblastic disease can occur months after any type of pregnancy

Confusing this rare cancer with other pregnancy complications

Common Mistakes

HCC Buddy guidance

O01.0-O01.9 — Hydatidiform mole; this is a precursor condition, not a malignancy

D39.2 — Neoplasm of uncertain behavior of placenta; use C58 only when malignancy is confirmed

C62.11/C62.12 — Testicular choriocarcinoma in males; different site, same histology

O36.0 — Maternal care for Rh isoimmunization; completely different pregnancy complication

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is C58 an HCC code?

Yes. C58 maps to Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24).

HCC Category Mapping

V28HCC 22, Bladder, Colorectal, and Other Cancers

0.363

V24HCC 10, Lymphoma and Other Cancers

0.675

ESRDHCC 10, Lymphoma and Other Cancers

0.111

RxHCCHCC 22, Cancer, Other Specified Sites

0.124

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work C58 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C58

For C58to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C58 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

C58 is the ICD-10-CM diagnosis code for malignant neoplasm of placenta. This is a rare cancer that develops in the placenta, the organ that nourishes a baby during pregnancy. It typically occurs during or shortly after pregnancy and requires immediate medical attention. C58 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of female genital organs (c51-c58).

Under the CMS-HCC V28 risk adjustment model, C58 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.363. Under the older CMS-HCC V24 model, C58 maps to Lymphoma and Other Cancers (HCC 10) with a community, non-dual, aged base RAF weight of 0.675. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This code is rarely used in clinical practice as placental cancers are extremely uncommon; verify documentation carefully and ensure the diagnosis is clearly stated by the physician. Because C58 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C58 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This code is rarely used in clinical practice as placental cancers are extremely uncommon; verify documentation carefully and ensure the diagnosis is clearly stated by the physician
•When coding this diagnosis, always include the trimester of pregnancy (O09.0-) or postpartum status codes if applicable, as this is a pregnancy-related malignancy

Clinical Significance

Malignant neoplasm of the placenta encompasses choriocarcinoma and other gestational trophoblastic neoplasias that arise from placental tissue. These are highly aggressive but also highly curable cancers that primarily affect women of reproductive age. They produce elevated beta-hCG levels and can metastasize rapidly, making early diagnosis critical for treatment success.

Documentation Requirements

✓Pathologic confirmation of placental malignancy (choriocarcinoma, invasive mole, or placental site trophoblastic tumor)
✓Beta-hCG levels and trend
✓Staging (FIGO staging system for gestational trophoblastic neoplasia)
✓Relationship to most recent pregnancy (molar pregnancy, normal pregnancy, ectopic, or abortion)
✓Metastatic workup results
✓Current treatment status (chemotherapy, surveillance)

Includes

choriocarcinoma NOS
chorionepithelioma NOS

Excludes 1, Do NOT code together

chorioadenoma (destruens) (D39.2)
hydatidiform mole NOS (O01.9)
invasive hydatidiform mole (D39.2)
male choriocarcinoma NOS (C62.9-)
malignant hydatidiform mole (D39.2)

Commonly Confused Codes

•O01.0-O01.9: Hydatidiform mole; this is a precursor condition, not a malignancy
•D39.2: Neoplasm of uncertain behavior of placenta; use C58 only when malignancy is confirmed
•C62.11/C62.12: Testicular choriocarcinoma in males; different site, same histology
•O36.0: Maternal care for Rh isoimmunization; completely different pregnancy complication

Code Hierarchy

└C58Malignant neoplasm of placenta

C58 ICD-10-CM Code: Malignant neoplasm of placenta

HCC Buddy Code Card

C58

Is C58 an HCC code?

HCC Category Mapping

MEAT Criteria for C58

Get the V28 RAF + MEAT cheat sheet

What This Code Means

Coding Tips

Clinical Significance

Documentation Requirements

Includes

Excludes 1, Do NOT code together

Commonly Confused Codes

Code Hierarchy

Work C58 in HCC Buddy