C90.31
BillableSolitary plasmacytoma in remission
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C90.31 an HCC code?
Yes. C90.31 maps to Lymphoma 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 C90.31
For C90.31 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 C90.31 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C90.31 is the ICD-10-CM diagnosis code for solitary plasmacytoma in remission. A single tumor made of plasma cells that is currently in remission with no active disease. C90.31 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, C90.31 maps to Lymphoma and Other Cancers (HCC 19) with a community, non-dual, aged base RAF weight of 0.105. Under the older V24 model, C90.31 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.
Confirm remission status is explicitly documented by the physician before coding. Because C90.31 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 C90.31 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm remission status is explicitly documented by the physician before coding
- •Verify this is truly a solitary lesion and not multiple myeloma
Clinical Significance
Solitary plasmacytoma in remission indicates the single bone lesion has responded to treatment, typically radiation therapy, with resolution of the tumor. Despite remission, lifelong surveillance is essential due to the significant long-term risk of progression to multiple myeloma. Monitoring includes serial serum and urine protein studies, complete blood counts, and periodic imaging to detect new bone lesions.
Documentation Requirements
- ✓Remission must be explicitly documented by the provider with imaging evidence showing resolution of the bone lesion.
- ✓Ongoing surveillance parameters including protein electrophoresis results, bone marrow status, and imaging schedule must be recorded.
- ✓Any structural damage from the original lesion requiring ongoing management should be documented.
Commonly Confused Codes
- •C90.30 (solitary plasmacytoma not in remission) indicates active disease.
- •C90.32 (solitary plasmacytoma in relapse) indicates recurrence.
- •C90.01 (multiple myeloma in remission) should be used if the disease has progressed to systemic myeloma.
- •Z85.79 is only for cured disease without ongoing surveillance needs.