Skip to content
HCC Buddy home

C73 ICD-10-CM Code: Malignant neoplasm of thyroid gland

C73 maps to CMS-HCC V28 23. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC73

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of thyroid and other endocrine glands (C73-C75)

C73

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of thyroid gland

Cancer that develops in the thyroid gland, a butterfly-shaped gland in the neck that produces hormones regulating metabolism.

Buddy the Bee presenting code insight

Buddy Insight

Malignant neoplasm of the thyroid gland is one of the more common endocrine malignancies, with papillary thyroid carcinoma being the most prevalent subtype.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 23

Coefficient HCC 23: 0.186 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 013

Code-level coefficient reference

ESRD/PACE

HCC 12

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C7Malignant neoplasms of thyroid and other endocrine glands (C73-C75)C73Malignant neoplasm of thyroid gland

Inclusion Terms

Official

No inclusion terms are included in this display for C73. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C73. Check the code and parent instructions in the Code Book.

Related Codes

Official

No related codes are included in this display for C73. Check the Code Book for the complete code path.

Includes

Official

No Includes notes are included in this display for C73. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for C73. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C73. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify any functional activity

Code Also

Official

No Code Also instructions are included in this display for C73. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Pathology report confirming malignancy with histological type (papillary, follicular, medullary, anaplastic, or poorly differentiated)
Current status — active disease vs. in remission vs. history of (Z85.850 for personal history)
Staging information (TNM staging) when available
Treatment status — post-thyroidectomy, radioactive iodine therapy, current surveillance

MEAT Support

HCC Buddy guidance
Pathology report confirming malignancy with histological type (papillary, follicular, medullary, anaplastic, or poorly differentiated)
Current status — active disease vs. in remission vs. history of (Z85.850 for personal history)
Staging information (TNM staging) when available
Treatment status — post-thyroidectomy, radioactive iodine therapy, current surveillance

Audit Caution

HCC Buddy guidance
Continuing to code C73 after treatment completion when the patient has no evidence of disease — should transition to Z85.850
Coding thyroid nodules or goiter as malignant without pathological confirmation
Not distinguishing between primary thyroid cancer and metastatic cancer involving the thyroid
Coding anaplastic thyroid carcinoma the same as well-differentiated types — while the ICD-10 code is the same, documentation should reflect the vastly different prognosis and treatment needs

Common Mistakes

HCC Buddy guidance
Z85.850 — Personal history of malignant neoplasm of thyroid: Use when cancer is resolved/in remission with no evidence of disease, not during active treatment
D34 — Benign neoplasm of thyroid gland: Thyroid adenomas and benign nodules are not malignant
E04.1 — Nontoxic single thyroid nodule: Thyroid nodules are not automatically malignant
D44.0 — Neoplasm of uncertain behavior of thyroid gland: Use when malignancy is not yet confirmed

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C73 an HCC code?

Yes. C73 (Malignant neoplasm of thyroid gland) maps to HCC 23, Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C73 is billable and maps to V28 HCC 23, Prostate, Breast, and Other Cancers and Tumors. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C73
Description
Malignant neoplasm of thyroid gland
HCC (V28)
HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF reference coefficient
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors
0.186
ESRDHCC 12, Breast/Prostate/and Other Cancers and Tumors
Not separately weighted
RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C73 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C73

For C73, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

C73 is the ICD-10-CM diagnosis code for malignant neoplasm of thyroid gland. Cancer that develops in the thyroid gland, a butterfly-shaped gland in the neck that produces hormones regulating metabolism. C73 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of thyroid and other endocrine glands (c73-c75).

Under the CMS-HCC V28 risk adjustment model, C73 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. No V24 mapping is shown for C73; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

This code does not differentiate between histological types (papillary, follicular, medullary, anaplastic); review pathology reports for histology if needed for treatment planning. For C73, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for C73 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •This code does not differentiate between histological types (papillary, follicular, medullary, anaplastic); review pathology reports for histology if needed for treatment planning
  • •Ensure documentation specifies thyroid gland involvement and not metastatic disease to the thyroid from another primary site

Clinical Significance

Malignant neoplasm of the thyroid gland is one of the more common endocrine malignancies, with papillary thyroid carcinoma being the most prevalent subtype. Despite generally favorable prognosis for well-differentiated types, this diagnosis carries meaningful risk adjustment weight and requires lifelong surveillance with thyroid function monitoring and cancer recurrence screening. Accurate coding distinguishes active malignancy from personal history of thyroid cancer.

Documentation Requirements

  • ✓Pathology report confirming malignancy with histological type (papillary, follicular, medullary, anaplastic, or poorly differentiated)
  • ✓Current status — active disease vs. in remission vs. history of (Z85.850 for personal history)
  • ✓Staging information (TNM staging) when available
  • ✓Treatment status — post-thyroidectomy, radioactive iodine therapy, current surveillance
  • ✓Thyroglobulin levels and thyroid function tests supporting ongoing monitoring

Use Additional Code

  • code to identify any functional activity

Commonly Confused Codes

  • •Z85.850: Personal history of malignant neoplasm of thyroid: Use when cancer is resolved/in remission with no evidence of disease, not during active treatment
  • •D34: Benign neoplasm of thyroid gland: Thyroid adenomas and benign nodules are not malignant
  • •E04.1: Nontoxic single thyroid nodule: Thyroid nodules are not automatically malignant
  • •D44.0: Neoplasm of uncertain behavior of thyroid gland: Use when malignancy is not yet confirmed
  • •C79.89: Secondary malignant neoplasm of other specified sites: Metastatic cancer TO the thyroid from another primary

Code Hierarchy

└C73Malignant neoplasm of thyroid gland
└C73Malignant neoplasm of thyroid gland

For C73, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C73 maps to CMS-HCC V28 category 23, Prostate, Breast, and Other Cancers and Tumors. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C73. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

Work C73 in HCC Buddy

Open C73 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro