Skip to content
HCC Buddy home

C84.10 ICD-10-CM Code: Sezary disease, unspecified site

C84.10 maps to CMS-HCC V28 17 (RAF 4.209). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

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

C84.10

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

Sezary disease, unspecified site

Sézary disease, an aggressive form of skin cancer involving abnormal white blood cells, when the specific location of lymph node involvement is not specified.

Buddy the Bee presenting code insight

Buddy Insight

Sezary disease at an unspecified site is an aggressive leukemic variant of cutaneous T-cell lymphoma characterized by erythroderma (generalized skin redness affecting most of the body surface), lymphadenopathy, and circulating malignant T-cells (Sezary cells) in the peripheral blood.

CMS-HCC V28

HCC 17

RAF 4.209

CMS-HCC V24

HCC 10

RAF 0.675

ACA/HHS

HCC 10

Varies by metal level

ESRD/PACE

HCC 10

RAF 0.111

RXHCC

HCC 19

RAF 1.949

Code Book Path

Official
C84Mature T/NK-cell lymphomas
C84.1Sezary disease
C84.10Sezary disease, unspecified site

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C84.10 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C84.10 in this effective period.

Related Child Codes

Official
C84.11Sezary disease, lymph nodes of head, face, and neck
C84.12Sezary disease, intrathoracic lymph nodes
C84.13Sezary disease, intra-abdominal lymph nodes
C84.14Sezary disease, lymph nodes of axilla and upper limb
C84.15Sezary disease, lymph nodes of inguinal region and lower limb

Includes

Official

ICD-10-CM does not list Includes notes for C84.10 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C84.10 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C84.10 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C84.10 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C84.10 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Skin biopsy confirming cutaneous T-cell lymphoma
Peripheral blood flow cytometry or morphology demonstrating circulating Sezary cells (atypical T-cells with cerebriform nuclei)
Documentation of erythroderma with body surface area involvement
Lymph node assessment and staging documentation

MEAT Support

HCC Buddy guidance
Skin biopsy confirming cutaneous T-cell lymphoma
Peripheral blood flow cytometry or morphology demonstrating circulating Sezary cells (atypical T-cells with cerebriform nuclei)
Documentation of erythroderma with body surface area involvement
Lymph node assessment and staging documentation

Audit Caution

HCC Buddy guidance
Coding Sezary disease as mycosis fungoides — they are clinically and prognostically distinct entities despite both being cutaneous T-cell lymphomas
Using dermatitis codes for the skin manifestations of Sezary disease instead of the lymphoma code
Not verifying the presence of circulating Sezary cells in blood work, which is required to distinguish Sezary from erythrodermic mycosis fungoides
Confusing reactive erythroderma with Sezary disease — blood work is essential for diagnosis

Common Mistakes

HCC Buddy guidance
C84.00 — Mycosis fungoides, unspecified site: Mycosis fungoides is primarily cutaneous without significant blood involvement; Sezary disease requires circulating malignant T-cells
C84.40 — Peripheral T-cell lymphoma, unspecified: Sezary disease is a specific form of T-cell lymphoma with defined diagnostic criteria
L53.9 — Erythematous condition, unspecified: Erythroderma from Sezary disease should be coded with the lymphoma code, not a dermatologic code

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 C84.10 an HCC code?

Yes. C84.10 (Sezary disease, unspecified site) maps to Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 4.209. It is billable for payment year 2026.

Coder answer: C84.10 is billable and maps to V28 HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C84.10
Description
Sezary disease, unspecified site
HCC (V28)
HCC 17 — Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
RAF
4.209
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
4.209
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 C84.10 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C84.10

For C84.10 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 C84.10 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

Get the V28 RAF + MEAT cheat sheet

One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

C84.10 is the ICD-10-CM diagnosis code for sezary disease, unspecified site. Sézary disease, an aggressive form of skin cancer involving abnormal white blood cells, when the specific location of lymph node involvement is not specified. C84.10 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, C84.10 maps to Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic (HCC 17) with a community, non-dual, aged base RAF weight of 4.209. Under the older CMS-HCC V24 model, C84.10 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.

Use this code only when the site of lymph node involvement cannot be determined from documentation. Because C84.10 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 C84.10 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use this code only when the site of lymph node involvement cannot be determined from documentation
  • •If site is documented, use a more specific code (C84.11-C84.16) instead

Clinical Significance

Sezary disease at an unspecified site is an aggressive leukemic variant of cutaneous T-cell lymphoma characterized by erythroderma (generalized skin redness affecting most of the body surface), lymphadenopathy, and circulating malignant T-cells (Sezary cells) in the peripheral blood. It is classified as Stage IVA or higher and carries a significantly worse prognosis than mycosis fungoides, with median survival of 2-4 years.

Documentation Requirements

  • ✓Skin biopsy confirming cutaneous T-cell lymphoma
  • ✓Peripheral blood flow cytometry or morphology demonstrating circulating Sezary cells (atypical T-cells with cerebriform nuclei)
  • ✓Documentation of erythroderma with body surface area involvement
  • ✓Lymph node assessment and staging documentation
  • ✓Treatment plan — typically systemic therapy required

Commonly Confused Codes

  • •C84.00: Mycosis fungoides, unspecified site: Mycosis fungoides is primarily cutaneous without significant blood involvement; Sezary disease requires circulating malignant T-cells
  • •C84.40: Peripheral T-cell lymphoma, unspecified: Sezary disease is a specific form of T-cell lymphoma with defined diagnostic criteria
  • •L53.9: Erythematous condition, unspecified: Erythroderma from Sezary disease should be coded with the lymphoma code, not a dermatologic code

Child Codes

C84.10Sezary disease, unspecified site
HCC 17
C84.11Sezary disease, lymph nodes of head, face, and neck
HCC 17
C84.12Sezary disease, intrathoracic lymph nodes
HCC 17
C84.13Sezary disease, intra-abdominal lymph nodes
HCC 17
C84.14Sezary disease, lymph nodes of axilla and upper limb
HCC 17
C84.15Sezary disease, lymph nodes of inguinal region and lower limb
HCC 17
C84.16Sezary disease, intrapelvic lymph nodes
HCC 17
C84.17Sezary disease, spleen
HCC 17
C84.18Sezary disease, lymph nodes of multiple sites
HCC 17
C84.19Sezary disease, extranodal and solid organ sites
HCC 17
C84.1ASezary disease, in remission
HCC 17

Code Hierarchy

└C84Mature T/NK-cell lymphomas└C84.1Sezary disease└C84.10Sezary disease, unspecified site
└C84.10Sezary disease, unspecified site

Because C84.10 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.

C84.10 maps to CMS-HCC V28 category 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. Because C84.10 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

Work C84.10 in HCC Buddy

Open C84.10 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro