2026 ICD-10-CM Diagnosis Code C84.01Mycosis fungoides, lymph nodes of head, face, and neck
ICD-10-CM Codes›C00–D49›C81-C96›C84
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 20
- Chronic Condition
C84.01 is a billable ICD-10-CM diagnosis code for mycosis fungoides, lymph nodes of head, face, and neck. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 11 through 13, 820 through 825, 840 through 842. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 22 closely related codes. Coders also document this condition as mycosis fungoides of facial lymph node. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Non-Hodgkin lymphoma.
For Medicare Advantage risk adjustment, C84.01 maps to CMS-HCC Category 20 (Lung and Other Severe Cancers) under the V28 model, adding a risk factor of about 1.136 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C84.01 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Mycosis fungoides of facial lymph node
- Mycosis fungoides of lymph nodes of head
- Mycosis fungoides of lymph nodes of head and neck
- Mycosis fungoides of lymph nodes of neck
- Neoplasm of lymph node of face
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Mycosis Fungoides
a chronic, malignant t-cell lymphoma of the skin. in the late stages, the lymph nodes and viscera are affected.Lymph Nodes
they are oval or bean shaped bodies (1 - 30 mm in diameter) located along the lymphatic system.
Patient EducationClinical
Lymphoma
Lymphoma is a cancer of a part of the immune system called the lymph system. There are many types of lymphoma. One type is Hodgkin disease. The rest are called non-Hodgkin lymphomas.
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Convert C84.01 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C84.01Overview
What is the ICD-10 code for mycosis fungoides, lymph nodes of head, face, and neck?
The ICD-10-CM code for mycosis fungoides, lymph nodes of head, face, and neck is C84.01 (sometimes written as C8401). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is C84.01 (Mycosis fungoides) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report mycosis fungoides, lymph nodes of head, face, and neck on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does C84.01 group to?
When mycosis fungoides, lymph nodes of head, face, and neck is the principal diagnosis on an inpatient stay, it groups to MS-DRG 11, 12, 13, 820, 821, 822, 823, 824, 825, 840, 841, 842, with relative weights from 1.0104 to 5.8648 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C84.01 a CC or MCC?
CMS lists C84.01 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 22 closely related codes in its exclusion list.
What is the ICD-9 equivalent of C84.01?
Under the General Equivalence Mappings, mycosis fungoides, lymph nodes of head, face, and neck converts to ICD-9-CM 202.11 (mycosis fungoides head). The mapping is approximate, so confirm the match fits the documentation.
What HCC is C84.01?
C84.01 (mycosis fungoides, lymph nodes of head, face, and neck) maps to CMS-HCC Category 20 (Lung and Other Severe Cancers), commonly written as HCC 20, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 10 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 19.
Does C84.01 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C84.01 adds a risk adjustment factor of about 1.136 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.672 to 1.214 depending on the payment segment). A more severe related category (HCC 17, HCC 18, and HCC 19) supersedes it when both are reported. See the full factor table on the HCC 20 category page.
