What is ICD-10 code C91.60?

C91.60 is the ICD-10-CM diagnosis code for Prolymphocytic leukemia of T-cell type not having achieved remission. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C91.60 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C91.60 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C91.60 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C91.60 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does C91.60 map to under V28?

C91.60 maps to CMS-HCC V28 19 (Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does C91.60 pay in RAF?

C91.60 carries a community, non-dual, aged (CNA) RAF weight of 1.798 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for C91.60?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C91.60, V28 maps to Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers at RAF 1.798 while V24 mapped to Lymphoma and Other Cancers at RAF 0.675. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports C91.60?

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 Because C91.60 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM C91.60: Prolymphocytic leukemia

C91.60 maps to CMS-HCC V28 19 (RAF 1.798). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

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Code lookupC91.60Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)

C91.60

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

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.

Buddy Insight

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.

CMS-HCC V28

Mapped

HCC 19

Myelodysplastic Syndromes, Mu...

RAF 1.798

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Mapped

HCC 10

HHS-HCC 10

Varies by metal level

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.111

RXHCC

Mapped

HCC 19

Lymphoma and Other Cancers

RAF 1.949

Code Book Path

Official

C91Lymphoid leukemia

C91.6Prolymphocytic leukemia of T-cell type

C91.60Prolymphocytic leukemia of T-cell type not having achieved remission

Inclusion Terms

Official

Prolymphocytic leukemia of T-cell type with failed remission
Prolymphocytic leukemia of T-cell type NOS

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C91.60 in this effective period.

Related Child Codes

Official

C91.61Prolymphocytic leukemia of T-cell type, in remission

C91.62Prolymphocytic leukemia of T-cell type, in relapse

Includes

Official

ICD-10-CM does not list Includes notes for C91.60 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C91.60 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C91.60 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C91.60 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C91.60 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

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.

MEAT Support

HCC Buddy guidance

Documentation must confirm T-cell immunophenotype (typically CD4+, CD8

Audit Caution

HCC Buddy guidance

T-PLL is distinct from T-cell large granular lymphocytic leukemia (T-LGL), which is indolent and uses a different code.

Do not confuse with Sezary syndrome (C84.1) despite both being mature T-cell malignancies with leukemic presentation.

Ensure cytogenetic confirmation to distinguish from other T-cell neoplasms.

The aggressive clinical course may lead to rapid changes in disease status between encounters.

Common Mistakes

HCC Buddy guidance

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.

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C91.60 an HCC code?

Yes. C91.60 (Prolymphocytic leukemia of T-cell type not having achieved remission) maps to Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 1.798. It is billable for payment year 2026.

Coder answer: C91.60 is billable and maps to V28 HCC 19, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C91.60
Description: Prolymphocytic leukemia of T-cell type not having achieved remission
HCC (V28): HCC 19 — Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers
RAF: 1.798
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 19, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers

1.798

V24HCC 10, Lymphoma and Other Cancers

0.675

ESRDHCC 10, Lymphoma and Other Cancers

0.111

RxHCCHCC 19, Lymphoma and Other Cancers

1.949

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work C91.60 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C91.60

For C91.60 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 C91.60 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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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.