C58 ICD-10-CM Code: Malignant neoplasm of placenta
C58 maps to CMS-HCC V28 22. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. 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
Coefficient HCC 22: 0.363 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
Context neededHCC 011
Coefficient needs member context
ESRD/PACE
Context neededHCC 10
Coefficient needs member context
RXHCC
Context neededHCC 22
Coefficient needs member context
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for C58. Check the code and parent instructions in the Code Book.
Excludes 2
OfficialNo Excludes 2 notes are included in this display for C58. Check the code and parent instructions in the Code Book.
Related Codes
No related codes are included in this display for C58. Check the Code Book for the complete code path.
Includes
Official- choriocarcinoma NOS
- chorionepithelioma NOS
- malignant neoplasm of skin of female genital organsInherited from C51-C58
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
OfficialNo Code First sequencing instructions are included in this display for C58. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C58. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C58. Check the code and parent instructions in the Code Book.
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 review for C58
For C58, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
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. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. 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. For C58, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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