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C80.1 ICD-10-CM Code: Malignant (primary) neoplasm, unspecified

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
4 inclusion terms · 3 Excludes1
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 12

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 826 — MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASMS WITH MAJOR O.R. PROCEDURES WITH MCC (MDC 17)
  • MS-DRG 827 — MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASMS WITH MAJOR O.R. PROCEDURES WITH CC (MDC 17)
  • MS-DRG 828 — MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASMS WITH MAJOR O.R. PROCEDURES WITHOUT CC/MCC (MDC 17)
  • MS-DRG 829 — MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASMS WITH OTHER PROCEDURES WITH CC/MCC (MDC 17)
  • MS-DRG 830 — MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASMS WITH OTHER PROCEDURES WITHOUT CC/MCC (MDC 17)
  • MS-DRG 843 — OTHER MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASTIC DIAGNOSES WITH MCC (MDC 17)
  • MS-DRG 844 — OTHER MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASTIC DIAGNOSES WITH CC (MDC 17)
  • MS-DRG 845 — OTHER MYELOPROLIFERATIVE DISORDERS OR POORLY DIFFERENTIATED NEOPLASTIC DIAGNOSES WITHOUT CC/MCC (MDC 17)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 23 — Prostate, Breast, and Other Cancers and Tumors

Other models: CMS-HCC V22 HCC 12

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for C80.1 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on C80.1 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Cancer NOS
  • Cancer unspecified site (primary)
  • Carcinoma unspecified site (primary)
  • Malignancy unspecified site (primary)

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).

Coder workflow for C80.1

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

Before you code C80.1

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, C80.1 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).

    ReviewC80.2

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

  2. 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 →

  3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with C80.1. 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 record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — C80.1 is appropriate when the documentation goes no further.

    ReviewC80.2

  2. Does the documentation support a condition named in C80.1’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.

    ReviewC79.9, C7A.00

Consider C80.1. 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 C80.1(3 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with C80.1: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareC79.9, C7A.00

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

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).

ReviewC80.2

Documentation: Both the condition C80.1 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).

ReviewC79.9, C7A.00

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.

Code Overview

Malignant (primary) neoplasm, unspecified is a billable ICD-10-CM diagnosis code (C80.1).

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

Indexed Clinical Terms (11)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Neoplasm Table Sites (2)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Anatomical sites from the official ICD-10-CM Table of Neoplasms that map to this code, with the matching behavior column.

  • Neoplasm, neoplastic — Malignant, Primary
  • Neoplasm, neoplastic, unknown site or unspecified — Malignant, Primary

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Chapter 2: Neoplasms (C00-D49 )

k. Malignant neoplasm without specification of site Code C80.1, Malignant (primary) neoplasm, unspecified, equates to Cancer, unspecified. This code should only be used when no determination can be made as to the primary site of a malignancy. This code should rarely be used in the inpatient setting.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

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 C80.1 or its code family, from the CMS ICD-10-CM tabular instructional notes, the CMS Table of Neoplasms and the CMS Table of Neoplasms (site match derived from the code title). Tabular-note edges are stored at the code family level that carries each note.

Referenced by 2 Excludes1 notes: C76 — Malignant neoplasm of other and ill-defined sites, C79.9 — Secondary malignant neoplasm of unspecified site.

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

Referenced by 5 Same-site neoplasm codes: C79.9 — Secondary malignant neoplasm of unspecified siteCompare C80.1 vs C79.9 →, D09.9 — Carcinoma in situ, unspecifiedCompare C80.1 vs D09.9 →, D36.9 — Benign neoplasm, unspecified siteCompare C80.1 vs D36.9 →, D48.9 — Neoplasm of uncertain behavior, unspecifiedCompare C80.1 vs D48.9 →, D49.9 — Neoplasm of unspecified behavior of unspecified siteCompare C80.1 vs D49.9 →.

These codes represent related neoplasm behaviors affecting the same anatomic site.

Referenced by 1 Screening & history code: Z85.819 — Personal history of malignant neoplasm of unspecified site of lip, oral cavity, and pharynxCompare C80.1 vs Z85.819 →.

These codes represent screening tests and history codes that refer to this active disease condition.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 8 MS-DRGs: DRG 826 (MDC 17), DRG 827 (MDC 17), DRG 828 (MDC 17), DRG 829 (MDC 17), DRG 830 (MDC 17), DRG 843 (MDC 17), DRG 844 (MDC 17), DRG 845 (MDC 17).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):NEO071 — Malignant neoplasm, unspecified (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Prostate, Breast, and Other Cancers and Tumors) for risk-adjusted payment.

C76.1 — Malignant neoplasm of thorax, C76.2 — Malignant neoplasm of abdomen, C76.3 — Malignant neoplasm of pelvis, C76.40 — Malignant neoplasm of unspecified upper limb, C76.41 — Malignant neoplasm of right upper limb, C76.42 — Malignant neoplasm of left upper limb, C76.50 — Malignant neoplasm of unspecified lower limb, C76.51 — Malignant neoplasm of right lower limb, C76.52 — Malignant neoplasm of left lower limb, C76.8 — Malignant neoplasm of other specified ill-defined sites, C80.2 — Malignant neoplasm associated with transplanted organ, D03.0 — Melanoma in situ of lip, D03.10 — Melanoma in situ of unspecified eyelid, including canthus, D03.111 — Melanoma in situ of right upper eyelid, including canthus, D03.112 — Melanoma in situ of right lower eyelid, including canthus, D03.121 — Melanoma in situ of left upper eyelid, including canthus, D03.122 — Melanoma in situ of left lower eyelid, including canthus, D03.20 — Melanoma in situ of unspecified ear and external auricular canal, D03.21 — Melanoma in situ of right ear and external auricular canal, D03.22 — Melanoma in situ of left ear and external auricular canal, +213 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic, Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers, Lung and Other Severe Cancers, Lymphoma and Other Cancers, Bladder, Colorectal, and Other Cancers

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Malignant neoplasm, unspecified).

C80.0 — Disseminated malignant neoplasm, unspecified, C80.2 — Malignant neoplasm associated with transplanted organ, D09.9 — Carcinoma in situ, unspecified, Z19.1 — Hormone sensitive malignancy status, Z19.2 — Hormone resistant malignancy status

Same Index main term, other category

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

C7A.1 — Malignant poorly differentiated neuroendocrine tumors (neuroendocrine, high grade, any site), C7A.8 — Other malignant neuroendocrine tumors (neuroendocrine, specified NEC), C7B.00 — Secondary carcinoid tumors, unspecified site (carcinoid, secondary), C7B.01 — Secondary carcinoid tumors of distant lymph nodes (carcinoid, secondary, distant lymph nodes), C7B.02 — Secondary carcinoid tumors of liver (carcinoid, secondary, liver), C7B.03 — Secondary carcinoid tumors of bone (carcinoid, secondary, bone), C7B.04 — Secondary carcinoid tumors of peritoneum (carcinoid, mesentery metastasis), C7B.09 — Secondary carcinoid tumors of other sites (carcinoid, secondary, specified NEC), C7B.1 — Secondary Merkel cell carcinoma (secondary, Merkel cell), C7B.8 — Other secondary neuroendocrine tumors (neuroendocrine, secondary NEC), D05.0 — Lobular carcinoma in situ of breast (noninfiltrating, lobular, breast), D05.1 — Intraductal carcinoma in situ of breast (intraductal, breast), D06.0 — Carcinoma in situ of endocervix (cervix uteri, in situ, endocervix), D06.1 — Carcinoma in situ of exocervix (cervix uteri, in situ, exocervix), D06.7 — Carcinoma in situ of other parts of cervix (cervix uteri, in situ, specified site NEC), D06.9 — Carcinoma in situ of cervix, unspecified (cervix uteri, in situ), D13.7 — Benign neoplasm of endocrine pancreas (beta-cell, pancreas), D18.00 — Hemangioma unspecified site (glomus), D18.01 — Hemangioma of skin and subcutaneous tissue (glomus, skin), D18.02 — Hemangioma of intracranial structures (glomus, intracranial), +137 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Iron Panel

Contextual Map

Every relationship of C80.1 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 C80.1 with these 2 related codes in Claim Check

Hierarchy

Excludes1

Same site

Referenced by Excludes1 notes

Referenced by Same-site neoplasm codes

Referenced by Screening & history codes MedCoder-derived

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 23 — Prostate, Breast, and Other Cancers and Tumors [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 17 — Myeloproliferative Diseases and Disorders, Poorly Differentiated Neoplasms[MDC crossing]: “Myeloproliferative Diseases and Disorders, Poorly Differentiated Neoplasms — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 4,730 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Neoplasm sites

  • Neoplasm, neoplastic — Neoplasm, neoplastic — Malignant, Primary [Neoplasm table]: “Neoplasm, neoplastic (Malignant, Primary)”— CMS Table of Neoplasms · icd10cm-fy2026
  • Neoplasm, neoplastic, unknown site or unspecified — Neoplasm, neoplastic, unknown site or unspecified — Malignant, Primary [Neoplasm table]: “Neoplasm, neoplastic, unknown site or unspecified (Malignant, Primary)”— CMS Table of Neoplasms · icd10cm-fy2026

Index entries (11)

  • Cancer, unspecified site (primary)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Carcinoma (malignant), unspecified site (primary)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Malignancy, unspecified site (primary)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Sarcomatosis, unspecified site[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Tumor, malignant[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Tumor, malignant, fusiform cell (type)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Tumor, malignant, giant cell (type)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Tumor, malignant, mixed NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • and 3 more

Nearest codes

Change history

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

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 FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release 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.

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

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. "C80.1 — Malignant (primary) neoplasm, unspecified." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/c80.1-malignant-primary-neoplasm-unspecified

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Malignant (primary) neoplasm, unspecified

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), 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 C80.1 in its code family, with their registry titles.

View all codes in the C80 family