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C7B.1 ICD-10-CM Code: Secondary Merkel cell carcinoma

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

Coding at a Glance

Tabular directives
2 inclusion terms · 1 use-additional code
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 8 · RxHCC V08 category 18

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 v44, 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 17 — Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic (supersedes HCC 18, HCC 19, HCC 20, HCC 21, HCC 22, HCC 23)

Other models: CMS-HCC V22 HCC 8 · RxHCC V08 HCC 18

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 C7B.1 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 C7B.1 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Merkel cell carcinoma nodal presentation
  • Merkel cell carcinoma visceral metastatic presentation

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code to identify any functional activity

Source: inherited from C7B

Coder workflow for C7B.1

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

Before you code C7B.1

  1. 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 →

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.
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.
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).

Official instructions as workflow

  • Use Additional Code — after identifying C7B.1(1 note)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with C7B.1 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

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

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with C7B.1?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

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.

Code Overview

Secondary Merkel cell carcinoma is a billable ICD-10-CM diagnosis code (C7B.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 (4)

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.

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-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name C7B.1 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 2 Excludes1 notes: C79 — Secondary malignant neoplasm of other and unspecified sites (via C7B.-), C79.2 — Secondary malignant neoplasm of skin.

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

Referenced by 1 Code Also instruction: E34.0 — Carcinoid syndrome (via C7B.-).

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

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 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):NEO066 — Malignant neuroendocrine tumors (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 (Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic) for risk-adjusted payment.

C79.49 — Secondary malignant neoplasm of other parts of nervous system, C79.70 — Secondary malignant neoplasm of unspecified adrenal gland, C79.71 — Secondary malignant neoplasm of right adrenal gland, C79.72 — Secondary malignant neoplasm of left adrenal gland, C7B.00 — Secondary carcinoid tumors, unspecified site, C7B.01 — Secondary carcinoid tumors of distant lymph nodes, C7B.02 — Secondary carcinoid tumors of liver, C7B.03 — Secondary carcinoid tumors of bone, C7B.04 — Secondary carcinoid tumors of peritoneum, C7B.09 — Secondary carcinoid tumors of other sites, C7B.8 — Other secondary neuroendocrine tumors, C84.10 — Sézary disease, unspecified site, C84.11 — Sézary disease, lymph nodes of head, face, and neck, C84.12 — Sézary disease, intrathoracic lymph nodes, C84.13 — Sézary disease, intra-abdominal lymph nodes, C84.14 — Sézary disease, lymph nodes of axilla and upper limb, C84.15 — Sézary disease, lymph nodes of inguinal region and lower limb, C84.16 — Sézary disease, intrapelvic lymph nodes, C84.17 — Sézary disease, spleen, C84.18 — Sézary disease, lymph nodes of multiple sites, +57 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 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, Prostate, Breast, and Other Cancers and Tumors

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Malignant neuroendocrine tumors).

C7A.025 — Malignant carcinoid tumor of the sigmoid colon, C7A.026 — Malignant carcinoid tumor of the rectum, C7A.029 — Malignant carcinoid tumor of the large intestine, unspecified portion, C7A.090 — Malignant carcinoid tumor of the bronchus and lung, C7A.091 — Malignant carcinoid tumor of the thymus, C7A.092 — Malignant carcinoid tumor of the stomach, C7A.093 — Malignant carcinoid tumor of the kidney, C7A.094 — Malignant carcinoid tumor of the foregut, unspecified, C7A.095 — Malignant carcinoid tumor of the midgut, unspecified, C7A.096 — Malignant carcinoid tumor of the hindgut, unspecified, C7A.098 — Malignant carcinoid tumors of other sites, C7A.1 — Malignant poorly differentiated neuroendocrine tumors, C7A.8 — Other malignant neuroendocrine tumors, C7B.00 — Secondary carcinoid tumors, unspecified site, C7B.01 — Secondary carcinoid tumors of distant lymph nodes, C7B.02 — Secondary carcinoid tumors of liver, C7B.03 — Secondary carcinoid tumors of bone, C7B.04 — Secondary carcinoid tumors of peritoneum, C7B.09 — Secondary carcinoid tumors of other sites, C7B.8 — Other secondary neuroendocrine tumors, +10 more

Same Index main term, other category

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

C53.9 — Malignant neoplasm of cervix uteri, unspecified (solid, microinvasive, unspecified site), C56 — Malignant neoplasm of ovary (granulosa cell), C56.9 — Malignant neoplasm of unspecified ovary (papillocystic, unspecified site), C58 — Malignant neoplasm of placenta (chorionic, unspecified site, female), C61 — Malignant neoplasm of prostate (endometrioid, unspecified site, male), C62.90 — Malignant neoplasm of unspecified testis, unspecified whether descended or undescended (Sertoli cell, unspecified site), C64 — Malignant neoplasm of kidney, except renal pelvis (renal cell), C73 — Malignant neoplasm of thyroid gland (Hurthle cell), C74.0 — Malignant neoplasm of cortex of adrenal gland (adrenal cortical), C75.0 — Malignant neoplasm of parathyroid gland (water-clear cell), C75.1 — Malignant neoplasm of pituitary gland (basophil, unspecified site), C7A.1 — Malignant poorly differentiated neuroendocrine tumors (neuroendocrine, high grade, any site), C80.0 — Disseminated malignant neoplasm, unspecified (generalized, with unspecified primary site), C80.1 — Malignant (primary) neoplasm, unspecified (unspecified site), 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), +33 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.

Alpha-Fetoprotein (AFP) Test, CEA Test, Fecal Occult Blood Test (FOBT), Gamma-glutamyl Transferase (GGT) Test, Iron Panel, Prothrombin Time Test and INR (PT/INR)

Contextual Map

Every relationship of C7B.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 C7B.1 with these 3 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Code Also instructions

  • E34.0 — Carcinoid syndrome[Code Also](via C7B.-): “secondary neuroendocrine tumors (C7B.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 17 — Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic [CMS-HCC]: “Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic — supersedes HCC 18 (Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid), HCC 19 (Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers), HCC 20 (Lung and Other Severe Cancers), HCC 21 (Lymphoma and Other Cancers), HCC 22 (Bladder, Colorectal, and Other Cancers), HCC 23 (Prostate, Breast, and Other Cancers and Tumors)”— 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. 4,735 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Index entries

  • Carcinoma (malignant), Merkel cell, nodal presentation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Carcinoma (malignant), Merkel cell, secondary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Carcinoma (malignant), Merkel cell, visceral metastatic[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Carcinoma (malignant), secondary, Merkel cell[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027

Nearest codes (9)

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.

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
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 — v44 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-derived 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 editorial 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-derived relationship · MedCoder editorial 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. "C7B.1 — Secondary Merkel cell carcinoma." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/c7b.1-secondary-merkel-cell-carcinoma

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Secondary Merkel cell carcinoma

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 C7B.1 in its code family, with their registry titles.

View all codes in the C7B family