C91.52
BillableAdult T-cell lymphoma/leukemia (HTLV-1-associated), in relapse
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C91.52 an HCC code?
Yes. C91.52 maps to Myelodysplastic Syndromes, Multiple Myeloma, 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 C91.52
For C91.52to 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 C91.52 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C91.52 is the ICD-10-CM diagnosis code for adult t-cell lymphoma/leukemia (htlv-1-associated), in relapse. This is a type of blood cancer caused by the HTLV-1 virus that affects T-cells (a type of white blood cell) in adults, and the cancer has returned after a period of improvement or remission. It is an aggressive form of leukemia/lymphoma that requires immediate treatment. C91.52 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of lymphoid, hematopoietic and related tissue (c81-c96).
Under the CMS-HCC V28 risk adjustment model, C91.52 maps to Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers (HCC 19) with a community, non-dual, aged base RAF weight of 1.798. Under the older CMS-HCC V24 model, C91.52 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.
Verify the relapse status is documented in the medical record before assigning the 'in relapse' code; initial diagnosis or remission would use different fifth characters (C91.50 for in remission, C91.51 for not in remission). Because C91.52 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 C91.52 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the relapse status is documented in the medical record before assigning the 'in relapse' code; initial diagnosis or remission would use different fifth characters (C91.50 for in remission, C91.51 for not in remission)
- •Confirm HTLV-1 association is explicitly documented, as this distinguishes adult T-cell lymphoma/leukemia from other T-cell malignancies and affects treatment protocols
Clinical Significance
Adult T-cell lymphoma/leukemia (HTLV-1-associated) in relapse indicates recurrence of this aggressive viral-driven malignancy after prior remission. Relapsed ATLL carries an extremely poor prognosis with very limited treatment options, and allogeneic stem cell transplantation may be the only potentially curative approach. The relapsed state often involves resistance to prior chemotherapy regimens and may show increased viral load.
Documentation Requirements
- ✓Documentation must confirm prior remission and current evidence of disease recurrence, including rising HTLV-1 viral load, recurrent cytopenias, new organ involvement, or hypercalcemia.
- ✓Prior treatment history, duration of remission, and planned salvage therapy should be recorded.
- ✓Updated staging including imaging and bone marrow assessment at relapse is essential.