What does ICD-10 code C84.9 mean?

ICD-10 code C84.9 is the standardized code used for mature t/nk-cell lymphomas, unspecified in medical records and coding systems.

When is ICD-10 code C84.9 used?

Doctors, hospitals, and insurers may use ICD-10 code C84.9 when recording mature t/nk-cell lymphomas, unspecified in a standardized format. This entry may also act as a broader category that points toward more specific child codes.

Does ICD-10 code C84.9 confirm a diagnosis?

No. A code helps standardize documentation and claims, but it should not be read as a substitute for a clinician's full assessment.

ICD10

ICD-10 Code C84.9: Mature T/NK-cell lymphomas, unspecified

Name: ICD-10 Code C84.9: Mature T/NK-cell lymphomas, unspecified
Creator: HealthAssure Clinical Team
Published: 2026-05-26T09:40:13.196Z

C84.9 is an ICD-10 diagnosis entry used to group records related to Mature T/NK-cell lymphomas, unspecified. You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Neoplasms (C00-D49).

Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Neoplasms (C00-D49).

When is it used?

May be used when a clinician documents mature t/nk-cell lymphomas, unspecified in a patient's medical record.
May appear in hospital records, claims, referrals, and clinical documentation.
This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

A code alone does not explain severity, treatment plan, or outcome.
A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter

2Neoplasms (C00-D49)

block

C00-C96Malignant neoplasms

block

C81-C96Malignant neoplasms of lymphoid, hematopoietic and related tissue

Official coding notes

Inclusion terms

NK/T cell lymphoma NOS

Excludes1 (do not code together)

mature T-cell lymphoma, not elsewhere classified (C84.4-)

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

OncologistGeneral Physician

Sibling codes

C84.0Mycosis fungoides C84.1Sézary disease C84.4Peripheral T-cell lymphoma, not elsewhere classified C84.6Anaplastic large cell lymphoma, ALK-positive C84.7Anaplastic large cell lymphoma, ALK-negative C84.ACutaneous T-cell lymphoma, unspecified C84.ZOther mature T/NK-cell lymphomas

Mapped diagnoses and classifications

SNOMED_CT 783541009high

Breast implant-associated anaplastic large-cell lymphoma

Source: SNOMED International ICD-10 map

SNOMED_CT 421418009high

Mature T-cell AND/OR NK cell neoplasm

Source: SNOMED International ICD-10 map

Coding guidelines

Compatibility

Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.

Legacy codes

C84.9

Replacement codes

C84.90 — Mature T/NK-cell lymphomas, unspecified, unspecified siteC84.91 — Mature T/NK-cell lymphomas, unspecified, lymph nodes of head, face, and neckC84.92 — Mature T/NK-cell lymphomas, unspecified, intrathoracic lymph nodesC84.93 — Mature T/NK-cell lymphomas, unspecified, intra-abdominal lymph nodesC84.94 — Mature T/NK-cell lymphomas, unspecified, lymph nodes of axilla and upper limbC84.95 — Mature T/NK-cell lymphomas, unspecified, lymph nodes of inguinal region and lower limbC84.96 — Mature T/NK-cell lymphomas, unspecified, intrapelvic lymph nodesC84.97 — Mature T/NK-cell lymphomas, unspecified, spleenC84.98 — Mature T/NK-cell lymphomas, unspecified, lymph nodes of multiple sitesC84.99 — Mature T/NK-cell lymphomas, unspecified, extranodal and solid organ sitesC84.9A — Mature T/NK-cell lymphomas, unspecified, in remission

Common synonyms

Mature T/NK-cell lymphomas, unspecifiedMature T/NK-cell lymphomas

Frequently asked questions

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.