C85.26 ICD-10-CM Code: Mediastinal (thymic) large B-cell lymphoma, intrapelvic lymph nodes
C85.26 maps to CMS-HCC V28 21 (RAF 0.671). Documentation must support MEAT. MEAT criteria · RAF calculator · free HCC coding tools
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
C85.26
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMediastinal (thymic) large B-cell lymphoma, intrapelvic lymph nodes
A specific type of large B-cell lymphoma originating in the thymus gland with involvement of lymph nodes located within the pelvis.
Buddy Insight
Mediastinal (thymic) large B-cell lymphoma involving intrapelvic lymph nodes indicates disease that has spread beyond the primary mediastinal origin.
CMS-HCC V28
MappedHCC 21
RAF 0.671
CMS-HCC V24
MappedHCC 10
RAF 0.675
ACA/HHS
MappedHCC 10
Varies by metal level
ESRD/PACE
MappedHCC 10
RAF 0.111
RXHCC
MappedHCC 21
RAF 0.410
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for C85.26 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C85.26 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C85.26 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C85.26 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C85.26 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C85.26 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C85.26 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 C85.26 an HCC code?
Yes. C85.26 (Mediastinal (thymic) large B-cell lymphoma, intrapelvic lymph nodes) maps to Lymphoma 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 0.671. It is billable for payment year 2026.
Coder answer: C85.26 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C85.26
- Description
- Mediastinal (thymic) large B-cell lymphoma, intrapelvic lymph nodes
- HCC (V28)
- HCC 21 — Lymphoma and Other Cancers
- RAF
- 0.671
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
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 C85.26 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for C85.26
For C85.26 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 C85.26 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
C85.26 is the ICD-10-CM diagnosis code for mediastinal (thymic) large b-cell lymphoma, intrapelvic lymph nodes. A specific type of large B-cell lymphoma originating in the thymus gland with involvement of lymph nodes located within the pelvis. C85.26 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, C85.26 maps to Lymphoma and Other Cancers (HCC 21) with a community, non-dual, aged base RAF weight of 0.671. Under the older V24 model, C85.26 mapped to the same category but with a base RAF weight of 0.675, V28 recalibrated weights across the entire model. 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 when mediastinal large B-cell lymphoma involves pelvic lymph nodes such as iliac, obturator, or sacral nodes. Because C85.26 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 C85.26 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code when mediastinal large B-cell lymphoma involves pelvic lymph nodes such as iliac, obturator, or sacral nodes
- •Ensure imaging documentation confirms intrapelvic lymph node involvement for accurate coding
Clinical Significance
Mediastinal (thymic) large B-cell lymphoma involving intrapelvic lymph nodes indicates disease that has spread beyond the primary mediastinal origin. This dissemination pattern affects prognosis and treatment approach, potentially requiring more aggressive regimens or radiation field modification. Extra-mediastinal spread occurs in a minority of cases and should be carefully documented for accurate staging.
Documentation Requirements
- ✓Original pathology confirming primary mediastinal (thymic) large B-cell lymphoma subtype with appropriate markers
- ✓Imaging or clinical confirmation of intrapelvic lymph nodes involvement beyond the primary mediastinal mass
- ✓Documentation that this represents spread from primary mediastinal disease, not a de novo lymphoma at this site
- ✓Complete staging showing both primary mediastinal disease and secondary involvement
Commonly Confused Codes
- •C83.3x (Diffuse large B-cell lymphoma at same site): PMBCL spreading to intrapelvic lymph nodes should still be coded as C85.2x, not as DLBCL
- •C85.1x (Unspecified B-cell lymphoma at same site): Use C85.2x when the mediastinal/thymic subtype is confirmed by pathology
- •C85.28 (PMBCL, lymph nodes of multiple sites): Use site-specific code when a single secondary site is involved; use C85.28 for multiple sites