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C4A.11 ICD-10-CM Code: Merkel cell carcinoma of right eyelid, including canthus

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Coder workflow for C4A.11

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

Before you code C4A.11

  1. C4A.11 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).

    ReviewC4A.111, C4A.112

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

  2. Laterality is coded in this family. Confirm the side documented — right, left, or bilateral — and select the matching code (this page’s code: right). The unspecified-side code applies only when the record states no side. Laterality is assigned from the documented side; where a bilateral code exists and both sides are documented, it is used instead of two unilateral codes (Guidelines I.B.13).

    ReviewC4A.12 · left, C4A.10 · unspecified

    Guide: Laterality coding →

  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 →

Choose the right path

  1. Does the documentation support one of the more specific codes beneath C4A.11?
    Yes → Select that code and continue the checks below on its own page.
    No → C4A.11 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewC4A.111, C4A.112

  2. Is the side documented?
    Yes → Select the code for the documented side (or the bilateral code when both sides are documented and one exists).
    No → Use the unspecified-side code only when the record states no side; a query is the alternative.

    ReviewC4A.12 · left, C4A.10 · unspecified

Consider C4A.11. 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.
Laterality
Right, left or bilateral as documented; unspecified only when the record states no side (Guidelines I.B.13).
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).

Coding decision scenarios

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

Documentation: The record documents the condition on one side only.

Coding question: Which code in this family applies?

Path: Select the sibling code for the documented side.

Reason: Laterality is assigned from the documented side; the unspecified-side code is for records that state no side (Guidelines I.B.13).

ReviewC4A.12 · left, C4A.10 · unspecified

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.

Don’t confuse C4A.11 with…

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

The codes most likely to be picked instead of C4A.11 — 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.

  • C4A.10— Specificity relationship (Review)

    Overlapping diagnoses in the same category.

    Overlapping codes in the same category — the documentation decides which is the more specific fit.

    What moves you there: A record that documents no more than “Merkel cell carcinoma of unspecified eyelid, including canthus” takes C4A.10; specificity in the record moves it back here.

    Full comparison: C4A.11 vs C4A.10 →

  • C4A.12— Laterality relationship (Review)

    Same condition; these differ only in which side is documented.

    The same condition on the other side; the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

    What moves you there: A documented left side moves the case to C4A.12.

    Full comparison: C4A.11 vs C4A.12 →

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

Merkel cell carcinoma of right eyelid, including canthus is a non-billable ICD-10-CM category code (C4A.11). 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

  • Not billable as written — a more specific code is required: C4A.111, C4A.112.

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 C4A.11 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 1 Excludes1 note: C44 — Other and unspecified malignant neoplasm of skin (via C4A.-).

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

Referenced by 2 Excludes2 notes: C43 — Malignant melanoma of skin (via C4A.-), C7A — Malignant neuroendocrine tumors (via C4A.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Clinical classification (AHRQ CCSR):NEO028 — Skin cancers - all other types (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 condition, opposite side

Same category and title, differing only in which side of the body is affected.

C4A.10 — Merkel cell carcinoma of unspecified eyelid, including canthus (unspecified)Compare C4A.11 vs C4A.10 →, C4A.12 — Merkel cell carcinoma of left eyelid, including canthus (left)Compare C4A.11 vs C4A.12 →

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Skin cancers - all other types).

C44.709 — Unspecified malignant neoplasm of skin of left lower limb, including hip, C44.791 — Other specified malignant neoplasm of skin of unspecified lower limb, including hip, C44.792 — Other specified malignant neoplasm of skin of right lower limb, including hip, C44.799 — Other specified malignant neoplasm of skin of left lower limb, including hip, C44.80 — Unspecified malignant neoplasm of overlapping sites of skin, C44.89 — Other specified malignant neoplasm of overlapping sites of skin, C44.90 — Unspecified malignant neoplasm of skin, unspecified, C44.99 — Other specified malignant neoplasm of skin, unspecified, C4A.0 — Merkel cell carcinoma of lip, C4A.10 — Merkel cell carcinoma of unspecified eyelid, including canthus, C4A.111 — Merkel cell carcinoma of right upper eyelid, including canthus, C4A.112 — Merkel cell carcinoma of right lower eyelid, including canthus, C4A.12 — Merkel cell carcinoma of left eyelid, including canthus, C4A.121 — Merkel cell carcinoma of left upper eyelid, including canthus, C4A.122 — Merkel cell carcinoma of left lower eyelid, including canthus, C4A.20 — Merkel cell carcinoma of unspecified ear and external auricular canal, C4A.21 — Merkel cell carcinoma of right ear and external auricular canal, C4A.22 — Merkel cell carcinoma of left ear and external auricular canal, C4A.30 — Merkel cell carcinoma of unspecified part of face, C4A.31 — Merkel cell carcinoma of nose, +85 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.

C25.4 — Malignant neoplasm of endocrine pancreas (islet cell, pancreas), C25.9 — Malignant neoplasm of pancreas, unspecified (islet cell, with exocrine, mixed, unspecified site), C30.0 — Malignant neoplasm of nasal cavity (Schneiderian, unspecified site), C34.90 — Malignant neoplasm of unspecified part of unspecified bronchus or lung (oat cell, unspecified site), C37 — Malignant neoplasm of thymus (thymic), C41.0 — Malignant neoplasm of bones of skull and face (odontogenic, upper jaw), C41.1 — Malignant neoplasm of mandible (odontogenic), C44.29 — Other specified malignant neoplasm of skin of ear and external auricular canal (ceruminous), C44.91 — Basal cell carcinoma of skin, unspecified (basal cell), C44.99 — Other specified malignant neoplasm of skin, unspecified (apocrine, unspecified site), C50.91 — Malignant neoplasm of breast of unspecified site, female (lipid-rich), C50.92 — Malignant neoplasm of breast of unspecified site, male (lipid-rich, male), 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), +20 more

Contextual Map

Every relationship of C4A.11 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 C4A.11 with these 3 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Excludes2 notes

Clinical classification (CCSR)

Nearest codes (32)

Change history (2)

Common coding questions

Can C4A.11 be billed directly?

No. C4A.11 (Merkel cell carcinoma of right eyelid, including canthus) 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.

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. "C4A.11 — Merkel cell carcinoma of right eyelid, including canthus." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/c4a.11-merkel-cell-carcinoma-of-right-eyelid-including-canthus

Change history

  • FY2019 — October 1, 2018
    Became a non-billable header
    FY2019 changes
  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Merkel cell carcinoma of right eyelid, including canthus

Nearest Codes in This Family

Official ICD-10-CM classifications closest to C4A.11 in its code family, with their registry titles.

View all codes in the C4A family