2026 ICD-10-CM Diagnosis Code C73Malignant neoplasm of thyroid gland

ICD-10-CM Codes›C00–D49›C73-C75›C73

ICD-10-CM C73
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C73 is a billable ICD-10-CM diagnosis code for malignant neoplasm of thyroid gland. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 11 through 13, 643 through 645. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Endocrine system cancers - thyroid.

For Medicare Advantage risk adjustment, C73 maps to CMS-HCC Category 23 (Prostate, Breast, and Other Cancers and Tumors) under the V28 model, adding a risk factor of about 0.186 for a community, non-dual, aged beneficiary in payment year 2026.

Code Identity

ICD-10-CM Code
C73
Billable Status
Yes — Valid for Submission
Code Describes
Malignant neoplasm of thyroid gland
Short Description
Malignant neoplasm of thyroid gland
Same as the full description in the CMS dataset.
Chapter
C73-C75
Malignant neoplasms of thyroid and other endocrine glands

Code Classification

ChapterC00–D49Neoplasms
SectionC73-C75Malignant neoplasms of thyroid and other endocrine glands
CategoryC73Malignant neoplasm of thyroid gland
This CodeC73Malignant neoplasm of thyroid gland

Medicare Risk Adjustment (HCC)Billing

C73 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.

CMS-HCC V28 Category (Payment Model)
HCC 23— Prostate, Breast, and Other Cancers and Tumors
Payment HCC · PY 2026 one of 234 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.186
community, non-dual, aged · ranges 0.186–0.237 across segments
Hierarchy
Superseded by HCC 17, HCC 18, HCC 19, HCC 20, HCC 21, and HCC 22
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 12
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 12 · ESRD (V21): HCC 12 · ESRD (V24): HCC 12
ESRD V21 weights: 0.046 dialysis, 0.156–0.194 functioning graft · ESRD V24 weights: 0.045 dialysis, 0.162–0.219 functioning graft
Part D (RxHCC)
RxHCC 22 — Prostate, Breast, Bladder, and Other Cancers and Tumors
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anaplastic thyroid carcinoma
  • Carcinoma of thyroid
  • Differentiated thyroid carcinoma
  • Diffuse sclerosing papillary thyroid carcinoma
  • Familial nonmedullary primary thyroid carcinoma
  • Familial papillary thyroid carcinoma with renal papillary neoplasia syndrome
  • Follicular neoplasm of thyroid
  • Follicular thyroid carcinoma
  • Hurthle cell carcinoma of thyroid
  • Local recurrence of malignant neoplasm of thyroid
  • Malignant neoplasm of thyroid gland
  • Medullary thyroid carcinoma
  • Metastatic anaplastic thyroid carcinoma
  • Metastatic malignant neoplasm to thyroid gland
  • Mixed follicular and papillary thyroid carcinoma
  • Neoplasm of thyroglossal duct
  • Oxyphilic adenocarcinoma
  • Papillary thyroid carcinoma
  • Papillary thyroid carcinoma with renal papillary neoplasia
  • Primary anaplastic thyroid carcinoma
  • Primary differentiated carcinoma of thyroid gland
  • Primary diffuse sclerosing papillary thyroid carcinoma
  • Primary follicular thyroid carcinoma
  • Primary Hurthle cell carcinoma of thyroid
  • Primary malignant neoplasm of thyroglossal duct
  • Primary malignant neoplasm of thyroid gland
  • Primary medullary thyroid carcinoma
  • Primary mixed follicular and papillary thyroid carcinoma
  • Primary oxyphilic adenocarcinoma
  • Primary papillary thyroid carcinoma
  • Primary papillary thyroid carcinoma with renal papillary neoplasia
  • Primary poorly differentiated carcinoma of thyroid gland
  • Primary undifferentiated carcinoma of thyroid gland

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Use Additional Code

  • code to identify any functional activity

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO050
Endocrine system cancers - thyroid
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary		Malig.
Secondary		Ca
in situ		BenignUncertainUnspec.
thyroglossal ductC73C79.89D09.3D34D44.0D49.7
thyroid (gland)C73C79.89D09.3D34D44.0D49.7

Patient EducationClinical

Thyroid Cancer

Thyroid cancer is a cancer that starts in the tissues of the thyroid. Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body's most important functions.

The full article covers:

  • What is thyroid cancer?
  • What are the different types of thyroid cancer?
  • Who is more likely to develop thyroid cancer?
  • What are the symptoms of thyroid cancer?
  • How is thyroid cancer diagnosed?
  • What are the treatments for thyroid cancer?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C73 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
193 Malign neopl thyroid
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C73Overview

What is the ICD-10 code for malignant neoplasm of thyroid gland?

The ICD-10-CM code for malignant neoplasm of thyroid gland is C73. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is C73 (Malignant neoplasm of thyroid gland) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of thyroid gland on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C73 group to?

When malignant neoplasm of thyroid gland is the principal diagnosis on an inpatient stay, it groups to MS-DRG 11, 12, 13, 643, 644, 645, with relative weights from 0.7683 to 5.4541 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C73?

Under the General Equivalence Mappings, malignant neoplasm of thyroid gland converts to ICD-9-CM 193 (malign neopl thyroid). The mapping is a direct match.

What HCC is C73?

C73 (malignant neoplasm of thyroid gland) maps to CMS-HCC Category 23 (Prostate, Breast, and Other Cancers and Tumors), commonly written as HCC 23, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 12 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 22.

Does C73 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, C73 adds a risk adjustment factor of about 0.186 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.186 to 0.237 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, HCC 20, HCC 21, and HCC 22) supersedes it when both are reported. See the full factor table on the HCC 23 category page.