C57.20
BillableMalignant neoplasm of unspecified round ligament
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C57.20 an HCC code?
Yes. C57.20 maps to Colorectal, Bladder, 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 C57.20
For C57.20 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 C57.20 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C57.20 is the ICD-10-CM diagnosis code for malignant neoplasm of unspecified round ligament. Cancer of the round ligament, a cord-like structure that helps support the uterus, when the specific side is not identified. C57.20 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, C57.20 maps to Colorectal, Bladder, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C57.20 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.
Use this code only when laterality is not documented; if side is specified, use C57.21 or C57.22. Because C57.20 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 C57.20 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Round ligament malignancies are extremely rare tumors arising from the fibromuscular cord that connects the uterus to the labia majora. Due to their rarity, they are often discovered incidentally during surgery for other pelvic conditions. Accurate site identification is essential because they may be confused with inguinal hernias or inguinal lymphadenopathy.
Documentation Requirements
- ✓Pathology confirmation that the tumor originates in the round ligament
- ✓Laterality (right or left) — query provider if not documented
- ✓Histologic type (most commonly leiomyosarcoma or endometrioid stromal sarcoma)
- ✓Whether tumor is primary or metastatic
- ✓Staging and treatment status
Commonly Confused Codes
- •C57.21/C57.22 — Laterality-specific round ligament codes; use when side is documented
- •C57.10-C57.12 — Broad ligament cancer; different anatomical structure
- •D28.2 — Benign neoplasm of uterine ligaments; confirm malignancy vs. benign leiomyoma
- •C49.5 — Malignant neoplasm of connective tissue of pelvis; round ligament is more specific if documented