C72.42
BillableMalignant neoplasm of left acoustic nerve
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C72.42 an HCC code?
Yes. C72.42 maps to Lung and Other Severe 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 C72.42
For C72.42 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 C72.42 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C72.42 is the ICD-10-CM diagnosis code for malignant neoplasm of left acoustic nerve. A malignant (cancerous) tumor of the left acoustic nerve, which is involved in hearing and balance on the left side. C72.42 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of eye, brain and other parts of central nervous system (c69-c72).
Under the CMS-HCC V28 risk adjustment model, C72.42 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C72.42 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 specifies the left side; use C72.41 for right side and verify laterality in documentation. Because C72.42 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 C72.42 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code specifies the left side; use C72.41 for right side and verify laterality in documentation
- •Acoustic nerve tumors may present with hearing loss or balance problems; document affected side clearly
Clinical Significance
Malignant neoplasm of the left acoustic nerve is the left-sided counterpart of this rare cranial nerve VIII malignancy. As with right-sided disease, the key clinical challenge is distinguishing true malignancy from the much more common benign vestibular schwannoma. Documentation must clearly support malignant behavior to justify this code.
Documentation Requirements
- ✓Pathology report explicitly confirming malignancy of the left acoustic nerve
- ✓Imaging confirmation of left-sided involvement
- ✓Audiometric and vestibular function testing for the left ear
- ✓Tumor characteristics including size, invasiveness, and growth pattern
- ✓Current treatment status and surveillance plan
Commonly Confused Codes
- •C72.41 — Malignant neoplasm of right acoustic nerve: Verify left laterality
- •D33.3 — Benign neoplasm of cranial nerves: Benign schwannomas must not be coded as malignant
- •C72.40 — Unspecified acoustic nerve: Use C72.42 when left side is documented
- •H90.3 — Sensorineural hearing loss, bilateral: A symptom that may result from acoustic nerve pathology, not the tumor itself