C91.60
BillableProlymphocytic leukemia of T-cell type not having achieved remission
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C91.60 an HCC code?
Yes. C91.60 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 C91.60
For C91.60to 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 C91.60 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C91.60 is the ICD-10-CM diagnosis code for prolymphocytic leukemia of t-cell type not having achieved remission. This is a type of blood cancer where abnormal T-cells (a type of white blood cell) multiply uncontrollably, and the patient has not responded to treatment or achieved remission. Prolymphocytic leukemia is a rare and aggressive form of leukemia. C91.60 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, C91.60 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, C91.60 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 remission status in the medical record before coding - this code specifically indicates the patient has NOT achieved remission, which is critical for accurate coding. Because C91.60 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 C91.60 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the remission status in the medical record before coding - this code specifically indicates the patient has NOT achieved remission, which is critical for accurate coding
- •Ensure you have documentation of the T-cell type confirmation, as this distinguishes it from B-cell prolymphocytic leukemia (C91.40), and confirm this is the current status at the time of encounter
Clinical Significance
T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive mature T-cell neoplasm with a median age of onset in the mid-60s. T-PLL typically presents with rapidly rising lymphocyte counts, hepatosplenomegaly, lymphadenopathy, and skin infiltration. The 'not in remission' designation indicates active disease, which carries a very poor prognosis with median survival historically less than 2 years without effective treatment.
Documentation Requirements
- ✓Documentation must confirm T-cell immunophenotype (typically CD4+, CD8
- ✓or CD4+CD8+) with prolymphocytic morphology in peripheral blood. Cytogenetic findings including inv(14)(q11q32) or t(14;14)(q11;q32) and TCL1 expression should be documented. Active disease status must be explicitly stated, along with current disease burden including lymphocyte count, organ involvement, and skin manifestations.
Commonly Confused Codes
- •C91.30 (B-cell prolymphocytic leukemia) is the B-cell counterpart with different biology.
- •C91.50 (adult T-cell lymphoma/leukemia, HTLV-1-associated) is virally driven and distinct from T-PLL.
- •C91.10 (B-CLL not in remission) is a different disease entity.
- •C91.90 (lymphoid leukemia, unspecified) should not be used when T-PLL is specifically diagnosed.