C58 ICD-10-CM Code: Malignant neoplasm of placenta
C58 maps to CMS-HCC V28 22. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · HCC Buddy coding tools
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of female genital organs (C51-C58)
C58
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant 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
MappedHCC 22
Code-level coefficient reference
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for C58 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C58 in this effective period.
Related Child Codes
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
OfficialICD-10-CM does not list Code First sequencing instructions for C58 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C58 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C58 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is C58 an HCC code?
Yes. C58 (Malignant neoplasm of placenta) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: C58 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C58
- Description
- Malignant neoplasm of placenta
- HCC (V28)
- HCC 22 — Bladder, Colorectal, and Other Cancers
- RAF reference coefficient
- 0.363
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work C58 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT Criteria for C58
For C58 to 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 source-labeled community, non-dual, aged reference coefficient of 0.363. No V24 mapping is shown for C58; use the applicable model and payment year when reviewing the V28 mapping. 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. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
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 an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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, source-labeled coefficient references, 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
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