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

Billing Status: NO. This is a non-billable ICD-10-CM code: report a more specific billable code beneath it.

Coding at a Glance

Tabular directives
1 inclusion term · 2 Excludes1 · 4 Excludes2

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for C84.9 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on C84.9 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • NK/T cell lymphoma NOS

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from C81-C96

Coder workflow for C84.9

MedCoder structured workflow — derived from this code’s own official record

Before you code C84.9

  1. C84.9 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

    ReviewC84.90, C84.91, C84.92, C84.93, C84.94, C84.95, C84.96, C84.97, C84.98, C84.99, C84.9A

    See the relationships section · Guide: How to choose an ICD-10-CM code →

  2. Unspecified does not mean incorrect. When the record gives no greater specificity, C84.9 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

    ReviewC84.7

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

  3. Confirm the documented site and behavior (this code’s block classifies malignant neoplasms), whether the site is primary or secondary, and whether the malignancy is current or a personal history: a previously excised malignancy with no further treatment and no evidence of disease is history, not current disease. Verify the site against the Table of Neoplasms. Neoplasm chapter guidelines (Guidelines I.C.2.a, I.C.2.d, I.C.2.m).

    See the Table of Neoplasms entries · Guide: Active cancer vs history of cancer →

  4. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with C84.9. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support one of the more specific codes beneath C84.9?
    Yes → Select that code and continue the checks below on its own page.
    No → C84.9 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewC84.90, C84.91, C84.92, C84.93, C84.94, C84.95, C84.96, C84.97, C84.98, C84.99, C84.9A

  2. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — C84.9 is appropriate when the documentation goes no further.

    ReviewC84.7

  3. Does the documentation support a condition named in C84.9’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewC84.4, Z85.72

Consider C84.9. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
Anatomical site
At the most specific level the record states; a site the classification separates cannot be assumed from a procedure or a measurement.
Behavior and current-versus-history status
Malignant, in situ, benign or uncertain; primary or secondary; current disease or personal history (Guidelines I.C.2.m).
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Excludes1 — check before selecting C84.9(2 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with C84.9: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareC84.4, Z85.72

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of C84.9(4 notes)

    Coding workflow: The conditions named in this note are not included in C84.9. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareC46.3, C77, C79.52, C78.89

    See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific sibling code supportable?

Path: Review the specific siblings in this subcategory and what each requires the record to state.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

ReviewC84.7

Documentation: Both the condition C84.9 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewC84.4, Z85.72

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Coding context

The comparisons, hierarchy, index entries, guidelines, relationships, risk-adjustment and coverage context a coder commonly needs. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Don’t confuse C84.9 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of C84.9 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • C84.4— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of mature T-cell lymphoma, not elsewhere classified moves the case to C84.4; the two are not reported together unless documented as unrelated.

    Full comparison: C84.9 vs C84.4 →

  • Z85.72— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of personal history of non-Hodgkin lymphoma moves the case to Z85.72; the two are not reported together unless documented as unrelated.

    Full comparison: C84.9 vs Z85.72 →

  • C46.3— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of Kaposi's sarcoma of lymph nodes adds C46.3; it is not part of this code and both may be reported when both are documented.

    Full comparison: C84.9 vs C46.3 →

  • C77— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of secondary and unspecified neoplasm of lymph nodes adds C77; it is not part of this code and both may be reported when both are documented.

    Full comparison: C84.9 vs C77 →

  • C79.52— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of secondary neoplasm of bone marrow adds C79.52; it is not part of this code and both may be reported when both are documented.

    Full comparison: C84.9 vs C79.52 →

  • C78.89— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of secondary neoplasm of spleen adds C78.89; it is not part of this code and both may be reported when both are documented.

    Full comparison: C84.9 vs C78.89 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Code Overview

Mature T/NK-cell lymphomas, unspecified is a non-billable ICD-10-CM category code (C84.9). A more specific billable subcode must be selected for claims submission.

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name C84.9 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 7 Excludes1 notes: C26.1 — Malignant neoplasm of spleen (via C84.-), C76 — Malignant neoplasm of other and ill-defined sites (via C84.-), C77 — Secondary and unspecified malignant neoplasm of lymph nodes (via C84.-), C82 — Follicular lymphoma (via C84.-), C83.0 — Small cell B-cell lymphoma (via C84.-), C83.3 — Diffuse large B-cell lymphoma (via C84.-), C86 — Other specified types of T/NK-cell lymphoma (via C84.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 2 Code First instructions across 2 chapters: N16 — Renal tubulo-interstitial disorders in diseases classified elsewhere (via C84.-), Z15.0 — Genetic susceptibility to malignant neoplasm (via C84.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

Referenced by 1 Code Also instruction: D47.02 — Systemic mastocytosis (via C84.-).

These codes suggest coding this condition alongside when both are present.

Related Codes

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Lymphoma”; these codes share that main term but sit in a different category of the Tabular List.

C83.1 — Mantle cell lymphoma (mantle cell), C83.3 — Diffuse large B-cell lymphoma (diffuse large cell), C83.390 — Primary central nervous system lymphoma (primary central nervous system), C83.398 — Diffuse large B-cell lymphoma of other extranodal and solid organ sites (diffuse large cell, extranodal and solid organ sites NEC), C83.5 — Lymphoblastic (diffuse) lymphoma (T-precursor), C83.59 — Lymphoblastic (diffuse) lymphoma, extranodal and solid organ sites (primary central nervous system, lymphoblastic), C83.7 — Burkitt lymphoma (Burkitt), C83.79 — Burkitt lymphoma, extranodal and solid organ sites (primary central nervous system, Burkitt), C83.8 — Other non-follicular lymphoma (primary effusion B-cell), C83.9 — Non-follicular (diffuse) lymphoma, unspecified (non-follicular), C85.1 — Unspecified B-cell lymphoma (B-cell), C85.2 — Mediastinal (thymic) large B-cell lymphoma (mediastinallarge B-cell), C85.8 — Other specified types of non-Hodgkin lymphoma (non-Hodgkin, specified NEC), C85.9 — Non-Hodgkin lymphoma, unspecified (non-Hodgkin), C85.90 — Non-Hodgkin lymphoma, unspecified, unspecified site, C86.0 — Extranodal NK/T-cell lymphoma, nasal type (extranodal NK/T-cell, nasal type), C86.1 — Hepatosplenic T-cell lymphoma (hepatosplenic T-cell), C86.2 — Enteropathy-type (intestinal) T-cell lymphoma (enteropathy-typeT-cell), C86.3 — Subcutaneous panniculitis-like T-cell lymphoma (subcutaneous panniculitis-like T-cell), C86.4 — Blastic NK-cell lymphoma (blastic NK-cell), +24 more

Contextual Map

Every relationship of C84.9 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run C84.9 with these 11 related codes in Claim Check

Hierarchy

Excludes1

Referenced by Excludes1 notes

Referenced by Code First instructions

Referenced by Code Also instructions

Nearest codes (40)

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Deep reference

Published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Common coding questions

MedCoder editorial

Can C84.9 be billed directly?

No. C84.9 (Mature T/NK-cell lymphomas, unspecified) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 20, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "C84.9 — Mature T/NK-cell lymphomas, unspecified." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/c84.9-mature-tnk-cell-lymphomas-unspecified

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Mature T/NK-cell lymphomas, unspecified

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to C84.9 in its code family, with their registry titles.

View all codes in the C84 family