Q85.89
BillableOther phakomatoses, not elsewhere classified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q85.89 an HCC code?
Yes. Q85.89 maps to Melanoma and Other Skin Cancers under the CMS-HCC V28 risk adjustment model (and Breast, Prostate, and Other Cancers and Tumors 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 Q85.89
For Q85.89 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 Q85.89 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q85.89 is the ICD-10-CM diagnosis code for other phakomatoses, not elsewhere classified. This code represents other rare inherited disorders characterized by multiple tumors and abnormal tissue growths that are not specifically classified elsewhere. Q85.89 sits in the ICD-10-CM chapter for congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (q00-qa0), within the section covering other congenital malformations (q80-q89).
Under the CMS-HCC V28 risk adjustment model, Q85.89 maps to Melanoma and Other Skin Cancers (HCC 23) with a community, non-dual, aged base RAF weight of 0.251. Under the older CMS-HCC V24 model, Q85.89 maps to Breast, Prostate, and Other Cancers and Tumors (HCC 12) with a community, non-dual, aged base RAF weight of 0.150. 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 the specific phakomatosis is documented but does not fit Q85.0-Q85.83 categories. Because Q85.89 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 Q85.89 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
This code represents rare phakomatoses (neurocutaneous syndromes) not elsewhere classified that still carry significant implications for patient care including potential for tumor development and neurological complications. These conditions require specialized evaluation and often lifelong monitoring, even though they may be less well-characterized than the major phakomatoses.
Documentation Requirements
- ✓Specific phakomatosis type documented
- ✓Clinical features not meeting criteria for major syndromes
- ✓Neurological and cutaneous manifestations
- ✓Associated complications or comorbidities
- ✓Genetic testing results when available
- ✓Family history assessment
- ✓Reason other phakomatosis codes don't apply