🧬 ICD-10 CM C73 — Malignant Neoplasm Of Thyroid Gland
Billable Code Confirmed
ICD-10 CM C73 is a valid, 3-character billable ICD-10-CM code used to specify a primary malignant neoplasm of the thyroid gland. Unlike many codes in the neoplasm chapter, it does not require a 4th, 5th, or 6th character for laterality or specific anatomic sub-site within the gland. It is fully billable as-is for FY2026.
Non-Billable Parent Codes
Clinical Context
Selection of C73 requires a confirmed pathologic diagnosis of malignancy (e.g., papillary, follicular, medullary, or anaplastic carcinoma) originating in the thyroid gland. It should not be used for thyroid nodules or goiters that are merely “suspicious” for malignancy prior to definitive biopsy or surgical pathology results.
Code Classification
This is a diagnosis code used to establish medical necessity for oncologic surveillance, endocrinology management, and surgical interventions such as thyroidectomies or neck dissections. It is not a procedure code.
🔍 Code Description
ICD-10 CM C73 represents a primary malignant tumor originating within the tissues of the thyroid gland. The thyroid is an endocrine gland located in the anterior neck, responsible for producing hormones that regulate metabolism. Malignancies here most commonly present as papillary carcinoma (the most frequent and least aggressive type) or follicular carcinoma. Less common but more aggressive variants include medullary carcinoma (often associated with Multiple Endocrine Neoplasia syndromes) and anaplastic carcinoma, which carries a poor prognosis and requires rapid, aggressive intervention.
In inpatient and surgical coding, C73 is the primary driver of medical necessity for procedures ranging from a diagnostic lobectomy to a comprehensive total thyroidectomy with modified radical neck dissection. Because ICD-10-CM does not provide laterality for the thyroid gland, coders must rely on CPT modifiers (like -RT or -LT) to indicate laterality for partial resections. Accurate coding of this condition also requires careful review of the pathology report to ensure the malignancy is primary to the thyroid, rather than a secondary metastasis from another site, which would instead be coded to C79.89.
🌳 Code Tree / Hierarchy
C00-D49 Neoplasms ❌ Non-billable
│
├── C00-C75 Malignant neoplasms, stated or presumed to be primary, of specified sites, except of lymphoid, hematopoietic and related tissue ❌ Non-billable
│ │
│ ├── C69-C72 Malignant neoplasms of eye, brain and other parts of central nervous system ❌ Non-billable
│ ├── C73-C75 Malignant neoplasms of thyroid and other endocrine glands ❌ Non-billable
│ │ │
│ │ ├── C73 Malignant neoplasm of thyroid gland ◀ THIS CODE ✅ Billable
│ │ ├── C74 Malignant neoplasm of adrenal gland ❌ Non-billable
│ │ └── C75 Malignant neoplasm of other endocrine glands and related structures ❌ Non-billable
│ │
│ └── C76-C80 Malignant neoplasms of ill-defined, other secondary and unspecified sites ❌ Non-billableLaterality and Specificity Insight
Tip
Always wait for the final surgical pathology report before coding C73 on an inpatient discharge. If the patient is discharged before pathology is finalized, code the condition to the highest degree of certainty known at discharge (e.g., E04.9 for unspecified goiter or E04.1 for single thyroid nodule).
✅ Includes
- Papillary carcinoma of thyroid: The most common form of thyroid cancer, typically slow-growing and highly treatable.
- Follicular carcinoma of thyroid: The second most common type, which can occasionally spread to lungs or bones.
- Medullary carcinoma of thyroid: A cancer originating from the C cells of the thyroid, often requiring genetic testing for MEN2 mutations.
- Anaplastic carcinoma of thyroid: A rare, rapidly invasive, and highly malignant tumor.
❌ Excludes
Excludes 1
- C25.4 — Malignant neoplasm of endocrine pancreas (islet of Langerhans). These are distinct endocrine malignancies and cannot be coded together under the same primary site category.
- C37 — Malignant neoplasm of thymus. The thymus is anatomically distinct from the thyroid; primary malignancies here are mutually exclusive to primary thyroid malignancies in site classification.
Danger
The most common Excludes 1 error is attempting to code a primary malignancy of another endocrine gland (like the adrenal gland or thymus) using a generic endocrine cancer code alongside C73. Each primary site must be coded to its specific anatomic location.
Excludes 2
- C79.89 — Secondary malignant neoplasm of other specified sites. This can be coded alongside C73 if the patient has a primary thyroid cancer that has metastasized to another specified site not covered by other secondary codes.
- C77.0 — Secondary and unspecified malignant neoplasm of lymph nodes of head, face and neck. This is frequently coded with C73 when thyroid cancer metastasizes to the cervical lymph nodes, a common clinical scenario requiring neck dissection.
📋 Clinical Overview
Differentiating Thyroid Neoplasms
Accurate coding requires distinguishing between malignant, benign, and unspecified structural abnormalities of the thyroid gland.
| Feature | C73 | Related D34 | Related E04.9 |
|---|---|---|---|
| Pathology | Confirmed primary malignancy (e.g., papillary, follicular). | Confirmed benign neoplasm (e.g., follicular adenoma). | Nontoxic goiter or unspecified nodule; no neoplasm confirmed. |
| Treatment | Total thyroidectomy, lobectomy, radioactive iodine, neck dissection. | Lobectomy or observation. | Observation, medical management, or partial resection. |
| Risk Adjustment | Maps to an HCC category; significantly impacts RAF score. | Does not map to an HCC category. | Does not map to an HCC category. |
Important
A major Clinical Documentation Improvement (CDI) trigger is the use of terms like “suspicious for papillary carcinoma” or “neoplasm of uncertain behavior” in the H&P. Coders must query the provider or wait for final pathology to confirm if C73 is appropriate, rather than assuming malignancy based on preliminary fine-needle aspiration (FNA) results.
Manifestations & Symptom Burden
- Palpable Neck Mass: A painless, rapidly growing lump in the anterior neck is often the first clinical sign.
- Dysphagia: Difficulty swallowing due to the tumor compressing the esophagus.
- Hoarseness: Voice changes resulting from tumor invasion into the recurrent laryngeal nerve.
- Cervical Lymphadenopathy: Swollen lymph nodes in the neck indicating regional metastasis.
Tip
Symptoms that are integral to the malignancy (such as a palpable neck mass or hoarseness) are generally not coded separately when the definitive diagnosis of C73 is known, unless they require independent management.
💰 HCC Risk Adjustment
| HCC Category (V28) | HCC Category (V24) | RAF Weight (V28) | RAF Weight (V24) | Payer Impact |
|---|---|---|---|---|
| HCC 11 | HCC 10 | ⚠️ Verify | ⚠️ Verify | High |
The presence of C73 maps to HCC 11 (Colorectal, Breast, Kidney, and Other Cancers) in the V28 model. Capturing this code significantly impacts the patient’s Risk Adjustment Factor (RAF) score. To validly report this code for risk adjustment, the provider must document that the cancer is current and being actively managed (e.g., surgery, radioactive iodine, active surveillance, or adjuvant therapy). If the cancer has been fully excised and the patient is only receiving routine follow-up without active disease, the personal history code Z85.850 should be used instead, which does not carry the same HCC weight.
🏥 MS-DRG Assignment
| MS-DRG | Description | Relative Weight | Geometric Mean LOS |
|---|---|---|---|
| 625 | Thyroid, Parathyroid and Thyroglossal Procedures with MCC | ⚠️ Verify | ⚠️ Verify |
| 626 | Thyroid, Parathyroid and Thyroglossal Procedures with CC | ⚠️ Verify | ⚠️ Verify |
| 627 | Thyroid, Parathyroid and Thyroglossal Procedures without CC/MCC | ⚠️ Verify | ⚠️ Verify |
When a patient is admitted for surgical treatment of thyroid cancer (e.g., total thyroidectomy), C73 acts as the principal diagnosis, driving the MS-DRG assignment to the surgical tier 625-627 within MDC 10. The presence of secondary diagnoses, such as metastasis to cervical lymph nodes (C77.0) or unrelated chronic conditions (e.g., severe COPD or acute kidney injury), will determine if the encounter groups to a CC or MCC tier, significantly impacting facility reimbursement. Noridian MAC LCDs require clear documentation of medical necessity for inpatient admission versus outpatient observation for thyroidectomies, often hinging on the extent of the surgery (e.g., concurrent radical neck dissection) or patient comorbidities.
🔗 Related ICD-10-CM Codes
Benign and Uncertain Neoplasms:
- D34 — Benign neoplasm of thyroid gland
- D44.0 — Neoplasm of uncertain behavior of thyroid gland
- E04.1 — Nontoxic single thyroid nodule
Metastasis and History:
- C77.0 — Secondary and unspecified malignant neoplasm of lymph nodes of head, face and neck
- C78.00 — Secondary malignant neoplasm of unspecified lung
- C79.51 — Secondary malignant neoplasm of bone
- Z85.850 — Personal history of malignant neoplasm of thyroid
🛠️ Commonly Associated CPT Codes
- 60240 — Thyroidectomy, total or complete. Billed when the entire thyroid gland is removed due to malignancy.
- 60220 — Total thyroid lobectomy, unilateral; with or without isthmusectomy. Billed for removal of one entire lobe.
- 60210 — Partial thyroid lobectomy, unilateral; with or without isthmusectomy. Billed for subtotal removal of a lobe.
- 60252 — Thyroidectomy, total or subtotal for malignancy; with limited neck dissection. Billed when central compartment lymph nodes are removed concurrently.
- 60254 — Thyroidectomy, total or subtotal for malignancy; with radical neck dissection. Billed for extensive lateral neck node clearance.
- 38724 — Cervical lymphadenectomy (modified radical neck dissection). Billed separately if performed without a concurrent thyroidectomy code that already includes it.
🏷️ Modifier Reference
| Modifier | Name | When to Apply |
|---|---|---|
| -RT | Right Side | Append to unilateral procedures like 60220 to indicate the right thyroid lobe was removed. |
| -LT | Left Side | Append to unilateral procedures like 60220 to indicate the left thyroid lobe was removed. |
| -50 | Bilateral | Append if a typically unilateral procedure is performed on both sides (Note: Do not use on 60240 as total thyroidectomy is inherently bilateral). |
| -22 | Increased Procedural Services | Append if the thyroidectomy was exceptionally difficult (e.g., severe scarring, massive tumor invasion requiring extensive dissection). |
| -51 | Multiple Procedures | Append when multiple distinct procedures are performed in the same session (e.g., separate distinct lymph node excisions). |
| -59 | Distinct Service | Append to indicate a procedure is distinct and independent from other services performed on the same day, bypassing NCCI edits. |
| -78 | Return to OR | Append if the patient returns to the OR during the global period for a related complication (e.g., postoperative neck hematoma evacuation). |
| -79 | Unrelated Procedure | Append if an unrelated procedure is performed by the same physician during the postoperative global period. |
NCCI Bundling Considerations
Total thyroidectomy (60240) inherently includes the removal of both lobes and the isthmus; you cannot bill lobectomy codes (60220) alongside it. Additionally, if a thyroidectomy for malignancy includes a neck dissection (60252 or 60254), you cannot separately bill standalone cervical lymphadenectomy codes (38724) for the same anatomic region, as they are bundled into the comprehensive oncologic resection code.
🔬 ICD-10-PCS Crosswalk
- 0GTK0ZZ — Resection of Thyroid Gland, Open Approach. Used for a total open thyroidectomy.
- 0GTK4ZZ — Resection of Thyroid Gland, Percutaneous Endoscopic Approach. Used for minimally invasive/endoscopic total thyroidectomy.
- 0GTH0ZZ — Resection of Right Thyroid Gland Lobe, Open Approach. Used for an open right lobectomy.
- 0GTJ0ZZ — Resection of Left Thyroid Gland Lobe, Open Approach. Used for an open left lobectomy.
💊 Coding Scenarios and Examples
Example 1
Clinical Scenario:
A 45-year-old female presents for a scheduled total thyroidectomy. Previous fine-needle aspiration (FNA) of a right-sided nodule was positive for papillary thyroid carcinoma. The surgeon performs an open total thyroidectomy. The final surgical pathology report confirms papillary carcinoma confined to the thyroid gland with no lymph node involvement.
| Field | Code | Rationale |
|---|---|---|
| CPT | 60240 | Total thyroidectomy performed for malignancy. No modifiers needed as the code is inherently bilateral/complete. |
| PDx | C73 | Confirmed primary malignant neoplasm of the thyroid gland. |
Tip
Because the pathology confirmed the malignancy, C73 is the correct principal diagnosis. Do not code the nodule or goiter, as the definitive malignant diagnosis supersedes the symptom/sign codes.
Example 2
Clinical Scenario:
A 55-year-old male with known medullary thyroid carcinoma undergoes a total thyroidectomy with a modified radical neck dissection due to clinically positive cervical lymph nodes. Pathology confirms medullary carcinoma of the thyroid with metastasis to 4 out of 15 right cervical lymph nodes.
| Field | Code | Rationale |
|---|---|---|
| CPT | 60254 | Thyroidectomy, total or subtotal for malignancy; with radical neck dissection. |
| PDx | C73 | Primary site of the malignancy is the thyroid gland. |
| SDx | C77.0 | Secondary malignant neoplasm of lymph nodes of head, face, and neck. |
Tip
Example 3
Clinical Scenario:
A 30-year-old female undergoes a left thyroid lobectomy for a rapidly enlarging nodule that was “suspicious for follicular neoplasm” on FNA. The surgeon removes the left lobe and isthmus. The patient is discharged the next day. Three days later, the final pathology report returns showing a benign follicular adenoma.
| Field | Code | Rationale |
|---|---|---|
| CPT | 60220--LT | Total unilateral thyroid lobectomy. The -LT modifier indicates the left side. |
| PDx | D34 | Benign neoplasm of the thyroid gland, as confirmed by the final pathology report. |
Tip
⚠️ Coding Pitfalls and Tips
- Pitfall 1: Coding C73 based on preliminary FNA results that state “suspicious for malignancy.” Tips: Always wait for the final surgical pathology report for inpatient coding. If pathology is benign, code D34 or the appropriate goiter/nodule code.
- Pitfall 2: Using C73 for a patient who had their thyroid removed 5 years ago and is currently on Levothyroxine with no evidence of disease. Tips: Use Z85.850 (Personal history of malignant neoplasm of thyroid) and E89.0 (Postprocedural hypothyroidism). C73 is only for active cancer.
- Pitfall 3: Forgetting to code secondary metastatic sites. Tips: Always review the pathology report for lymph node involvement. If positive, add C77.0 to ensure accurate severity of illness and DRG capture.
- Pitfall 4: Appending laterality modifiers to total thyroidectomy codes. Tips: CPT 60240 inherently includes both lobes. Do not append -50, -RT, or -LT. Reserve laterality modifiers for lobectomies (60220, 60210).
- Pitfall 5: Unbundling neck dissections from comprehensive oncologic thyroidectomy codes. Tips: If the surgeon performs a total thyroidectomy with a radical neck dissection for cancer, use the combination code 60254 rather than billing 60240 and 38724 separately.
- Pitfall 6: Confusing primary thyroid cancer with secondary metastasis to the thyroid. Tips: If a patient has renal cell carcinoma that metastasized to the thyroid, the primary code is the kidney cancer, and the thyroid metastasis is coded as C79.89, not C73.
📚 Sources
1. AAPC. *ICD-10-CM Expert for Physicians and Hospitals.* AAPC; 2024. 2. Centers for Medicare & Medicaid Services (CMS). *ICD-10-CM Official Guidelines for Coding and Reporting FY 2024.* CMS; 2023. https://www.cms.gov/medicare/coding-billing/icd-10-codes/2024-icd-10-cm 3. American Medical Association (AMA). *CPT Professional Edition.* AMA; 2024.Sources listed above correspond to superscript citations throughout this note. Verify all Medicare payment figures against your current CMS PFS Lookup tool and applicable MAC LCD prior to claim submission. Please use the latest AAPC/AHIMA Coding Books to verify each code within this note.