C58
BillableMalignant neoplasm of placenta
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
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
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
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.
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
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