M31.2
BillableLethal midline granuloma
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M31.2 an HCC code?
Yes. M31.2 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease 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 M31.2
For M31.2to 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 M31.2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M31.2 is the ICD-10-CM diagnosis code for lethal midline granuloma. A rare, aggressive cancer-like condition that destroys tissues in the center of the face, including the nose and palate. M31.2 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering systemic connective tissue disorders (m30-m36).
Under the CMS-HCC V28 risk adjustment model, M31.2 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 93) with a community, non-dual, aged base RAF weight of 0.175. Under the older V24 model, M31.2 mapped to the same category but with a base RAF weight of 0.307 — 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.
This is a serious condition requiring careful documentation of affected sites. Because M31.2 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 M31.2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a serious condition requiring careful documentation of affected sites
- •Distinguish from granulomatosis with polyangiitis (Wegener's) which has different treatment
Clinical Significance
Lethal midline granuloma is a rare, aggressive lymphoproliferative disorder that primarily affects the nasal cavity and paranasal sinuses with progressive tissue destruction. Despite its name, it can be successfully treated with radiation therapy, but early recognition is crucial for optimal outcomes.
Documentation Requirements
- ✓Clinical presentation of destructive midline facial lesions
- ✓Biopsy showing characteristic lymphoid infiltration
- ✓Imaging demonstrating extent of tissue destruction
- ✓Immunohistochemical studies for lymphoma markers
- ✓Staging workup for systemic involvement
- ✓Response to radiation or chemotherapy
- ✓Monitoring for disease progression
- ✓Multidisciplinary oncology team involvement
Commonly Confused Codes
- •C77.0 — Secondary and unspecified malignant neoplasm of lymph nodes of head (when lymphomatous)
- •J34.2 — Deviated nasal septum (structural nasal problem)
- •M31.30 — Wegener's granulomatosis without renal involvement (different granulomatous condition)
- •C30.0 — Malignant neoplasm of nasal cavity (primary nasal malignancy)
- •K12.30 — Oral mucositis, unspecified (mucosal inflammation only)