D47.09 ICD-10-CM Code: Other mast cell neoplasms of uncertain behavior
HCC Buddy Code Card
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FY 2026 Apr update / Neoplasms (C00-D49) / Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (D37-D48)
D47.09
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther mast cell neoplasms of uncertain behavior
Other abnormal growths of mast cells that don't fit into the cutaneous or systemic categories.
Buddy Insight
Other mast cell neoplasms of uncertain behavior captures mast cell proliferative disorders that do not fit into the cutaneous or systemic mastocytosis categories.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
MappedHCC 21
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Extracutaneous mastocytoma
- Mast cell tumor NOS
- Mastocytoma NOS
- Mastocytosis NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for D47.09 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for D47.09 in this effective period.
Excludes 1
Official- congenital cutaneous mastocytosis (Q82.2)
- histiocytic neoplasms of uncertain behavior (D47.Z9)
- malignant mast cell neoplasm (C96.2-)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for D47.09 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for D47.09 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for D47.09 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is D47.09 an HCC code?
No. D47.09 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
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 D47.09
For D47.09to 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 D47.09 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
D47.09 is the ICD-10-CM diagnosis code for other mast cell neoplasms of uncertain behavior. Other abnormal growths of mast cells that don't fit into the cutaneous or systemic categories. D47.09 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (d37-d48).
D47.09 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
This code maps only to RxHCC 21 (Lymphoma and Other Cancers). It does not map to HCC V28, V24, or ESRD models. The limited HCC impact is consistent with other mast cell neoplasm codes in this category. Coders reviewing D47.09 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC, capturing the correct specificity is the highest-impact RAF improvement available within accurate coding.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for D47.09 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Other mast cell neoplasms of uncertain behavior captures mast cell proliferative disorders that do not fit into the cutaneous or systemic mastocytosis categories. This includes rare entities such as mast cell sarcoma and extracutaneous mastocytoma, which have unique clinical presentations and management approaches distinct from typical mastocytosis.
Documentation Requirements
- ✓Documentation should specify the type of mast cell neoplasm and explain why it does not meet criteria for cutaneous (D47.01) or systemic (D47.02) mastocytosis.
- ✓Tissue biopsy confirming mast cell proliferation is required.
- ✓Document the anatomical location, tryptase levels, KIT mutation status, and any associated symptoms.
Commonly Confused Codes
- •D47.01 (cutaneous mastocytosis) and D47.02 (systemic mastocytosis) are more specific and should be used when criteria are met.
- •C96.20 (malignant mast cell neoplasm) is used when malignant behavior is confirmed.
- •D47.9 (neoplasm of uncertain behavior of lymphoid/hematopoietic tissue, unspecified) is less specific and should not be used when a mast cell origin is established.