E04.1: Nontoxic single thyroid nodule

The ICD-10-CM code for one thyroid nodule that is not producing excess thyroid hormone and has not been established as malignant.

Billable

FY2027

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At a glance

Code Family

E04: Other nontoxic goiter.

Condition

Thyroid nodule

Billable

Yes

HCC Mapping (v28)

None. E04.1 carries no HCC weight in CMS-HCC v28.

DRG Grouping

MS-DRG 643, 644 or 645 (Endocrine Disorders) in MDC 10, endocrine, nutritional and metabolic diseases and disorders, under the FY2027 MS-DRG v44 grouper.

Family Specificity

Five billable child codes split on the structural pattern of the thyroid enlargement. E04.1 is the code for a solitary nontoxic nodule.

Which E04 code do I assign?

Category E04 splits on the structural pattern of the thyroid enlargement rather than on its severity. Assign E04.1 only when the record documents one discrete nodule and shows the gland is not overproducing hormone.

When documentation says…

Code

Single thyroid nodule, TSH normal

E04.1

Nontoxic single thyroid nodule. The note must describe one discrete nodule. It must also show the thyroid is not overproducing hormone.

Multiple thyroid nodules on ultrasound

E04.2

Nontoxic multinodular goiter. The note must describe more than one nodule without thyrotoxicosis.

Diffuse thyroid enlargement, no discrete nodule

E04.0

Nontoxic diffuse goiter. The note must describe generalized enlargement rather than nodular structure.

Hyperfunctioning nodule with suppressed TSH

E05.10

Thyrotoxicosis with toxic single thyroid nodule without thyrotoxic crisis or storm. Assign E05.11 instead when thyrotoxic crisis or storm is documented.

Biopsy confirms thyroid carcinoma

C73

Malignant neoplasm of thyroid gland. Once malignancy is established, C73 replaces E04.1 for that nodule.

Goiter attributed to iodine deficiency

E01.2

Iodine-deficiency related (endemic) goiter, unspecified. An Excludes1 note at category E04 bars reporting an iodine-deficiency goiter with E04.1 for the same goiter.

Goiter documented without stated structure

E04.9

Nontoxic goiter, unspecified. Use it when the record names a goiter but does not say diffuse, single nodule or multinodular.

Tabular notes

EXCLUDES1

Category E04 carries two Excludes1 notes. They apply to E04.1 and bar assigning both codes for the same condition. Congenital goiter, whether NOS, diffuse or parenchymatous, is classified to E03.0. Iodine-deficiency related goiter is classified to E00–E02. When the record documents either cause, assign the code from that category in place of E04.1.

FY2027: EFFECTIVE 1 OCTOBER 2026

The FY2027 codes and tabular addenda make no addition, deletion or revision in category E04. The code remains billable for the fiscal year beginning 1 October 2026. The Excludes1 notes at category E04 are unchanged. E04.1 carries no Excludes2, Use Additional or Code First instruction in FY2027.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which code is selected.

CMS-HCC v28 (PY2024+)

E04.1 does not map to any HCC category in CMS-HCC v28.

A benign thyroid nodule makes no contribution to a Medicare Advantage risk score.

MS-DRG v44 (FY2027)

E04.1 as a principal inpatient diagnosis groups to MS-DRG 643, 644 or 645 (Endocrine Disorders with MCC, with CC, or without CC/MCC) in MDC 10 under the FY2027 MS-DRG v44 grouper.

The resulting assignment depends on the full code set and the documented comorbidities.

Thyroid surgery such as thyroidectomy moves the encounter to the surgical DRG groupings.

Medicare and commercial payers

Medicare accepts E04.1 as support for medical necessity on thyroid ultrasound (CPT 76536), fine-needle aspiration biopsy (CPT 10005 and 10006 with ultrasound guidance) and thyroid function testing.

Surveillance imaging intervals for a thyroid nodule follow clinical guidelines.

Document nodule size, TIRADS category and the provider-directed follow-up plan.

V24 TO V28 TRANSITION

E04.1 carried no HCC weight in CMS-HCC v24.

It carries no HCC weight in CMS-HCC v28.

The move between the two models changes nothing for this code.

WHERE SPECIFICITY IS LOST

E04.9 records a goiter without stating its structure. It loses the solitary nodule detail that E04.1 carries.

E04.1 assigned after thyroid malignancy has been confirmed understates the encounter. C73 carries weight through the neoplasm HCC categories that E04.1 does not.

Documentation checklist to support E04.1

Chart elements that support code selection and reduce specificity-driven denials.

A single thyroid nodule, confirmed on physical examination or on imaging. The inclusion terms colloid nodule, thyroid cystic nodule NOS and nontoxic uninodular goiter also support E04.1.

Nontoxic status: thyroid function tests such as TSH and free T4 within normal limits, or a clinical statement that the nodule is not producing excess thyroid hormone.

Absence of confirmed malignancy, shown either by a benign biopsy result or by an evaluation still in progress.

The number of nodules, which separates a solitary nodule from multinodular goiter.

Nodule size and TIRADS category, where imaging has been performed.

The provider-directed follow-up plan for surveillance imaging or for biopsy.

Any hypothyroidism documented as a comorbidity alongside the nodule.

For a surgical encounter, the operative procedure performed, such as hemithyroidectomy or thyroid lobectomy.

FAQ

Is E04.1 a billable code?

Yes. E04.1 is a valid billable code for HIPAA-covered transactions. It has no child codes and takes no further characters.

When do I use E04.2 instead of E04.1?

Use E04.2 when the record documents more than one thyroid nodule. E04.1 is reserved for a solitary nodule. The distinction rests on the number of nodules described, not on their size.

Does E04.1 map to an HCC?

No. E04.1 does not map to any HCC category in CMS-HCC v28. It did not map to one in CMS-HCC v24 either. A benign thyroid nodule makes no contribution to a Medicare Advantage risk score.

If a biopsy result is indeterminate, can I still assign E04.1?

Yes. E04.1 is appropriate while malignancy has not been confirmed. An indeterminate result such as Bethesda category III or IV does not establish malignancy. Assign C73 only once thyroid cancer is documented.

What if the nodule is hyperfunctioning?

Assign E05.10 for thyrotoxicosis with a toxic single thyroid nodule without thyrotoxic crisis or storm. Assign E05.11 when a thyrotoxic crisis or storm is documented. E04.1 is limited to nontoxic nodules.

Can E04.1 be sequenced alongside C73?

No. E04.1 and C73 are not reported together for the same nodule. Once thyroid malignancy is established, C73 is the principal diagnosis for cancer-related encounters.

What changed for E04.1 in FY2027?

E04.1 is unchanged in the FY2027 update. The FY2027 update, effective 1 October 2026, makes no addition, deletion or revision in category E04. The Excludes1 notes at category E04 remain in place.

How does E04.1 differ between the inpatient and outpatient settings?

In the outpatient setting E04.1 supports nodule monitoring, ultrasound follow-up and biopsy planning. On the inpatient side it supports thyroid surgery such as hemithyroidectomy or thyroid lobectomy. In a surgical encounter the DRG grouping follows the operative procedure.

Related codes

Codes in the same family as E04.1. Only codes with a published page render as links.

Sibling codes in the E04 family

E04.0: Nontoxic diffuse goiter.
E04.2: Nontoxic multinodular goiter.
E04.8: Other specified nontoxic goiter.
E04.9: Nontoxic goiter, unspecified.

Additional codes to consider

Codes outside the E04 family considered alongside E04.1.

Consider instead

E04.2: Nontoxic multinodular goiter, when more than one nodule is documented.
E04.0: Nontoxic diffuse goiter, when the enlargement is diffuse rather than nodular.
E05.10: Thyrotoxicosis with toxic single thyroid nodule without thyrotoxic crisis or storm.
E05.11: Thyrotoxicosis with toxic single thyroid nodule with thyrotoxic crisis or storm.
C73: Malignant neoplasm of thyroid gland, once thyroid cancer is confirmed.
E01.2: Iodine-deficiency related (endemic) goiter, unspecified, barred from co-coding with E04.1 by an Excludes1 note.
E03.0: Congenital hypothyroidism with diffuse goiter, barred from co-coding with E04.1 by an Excludes1 note.

Sources

All claims on this page derive from government and professional-standards sources.

National Center for Health Statistics. (2026). International classification of diseases, tenth revision, clinical modification (ICD-10-CM) FY2027 files. https://www.cdc.gov/nchs/icd/icd-10-cm/files.html
Centers for Medicare & Medicaid Services and National Center for Health Statistics. (2026). ICD-10-CM official guidelines for coding and reporting FY2027. https://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10CM/2027/ICD-10-CM-October-1-2026-FY27-Guidelines.pdf
Centers for Medicare & Medicaid Services. (2025). 2026 model software/ICD-10 mappings. https://www.cms.gov/medicare/payment/medicare-advantage-rates-statistics/risk-adjustment/2026-model-software-icd-10-mappings
Centers for Medicare & Medicaid Services. (2026). MS-DRG classifications and software, version 44. https://www.cms.gov/medicare/payment/prospective-payment-systems/acute-inpatient-pps/ms-drg-classifications-and-software