Editorial orientation provided by MedAPI — not part of the coding instruction.
Common Histologies
- Differentiated thyroid carcinoma
- Papillary thyroid carcinoma (PTC) – most common thyroid cancer subtype
- Follicular thyroid carcinoma (FTC) – differentiated follicular-cell-derived carcinoma
- Oncocytic thyroid carcinoma – follicular-cell-derived carcinoma with oncocytic differentiation
- Poorly differentiated thyroid carcinoma
- Intermediate biological behavior between differentiated and anaplastic thyroid carcinoma
- Anaplastic thyroid carcinoma
- Rare, undifferentiated and highly aggressive thyroid malignancy
- Medullary thyroid carcinoma (MTC)
- Neuroendocrine carcinoma originating from thyroid C cells
- May occur sporadically or as part of hereditary RET-associated syndromes
Common Symptoms
- Thyroid nodule or neck mass
- Increasing neck swelling
- Hoarseness or voice changes
- Difficulty swallowing (dysphagia)
- Shortness of breath or airway symptoms in locally advanced disease
- Neck discomfort or pain
Many differentiated thyroid cancers are asymptomatic and are detected during evaluation of a thyroid nodule or incidentally on imaging.
Diagnosis
Diagnosis typically combines:
- Thyroid and cervical lymph-node ultrasound
- Fine-needle aspiration (FNA) – cytological evaluation of suspicious thyroid nodules
- Histopathology – definitive characterization after tissue or surgical specimen evaluation when required
- Thyroid function testing – primarily used to characterize thyroid function and nodule evaluation rather than to establish malignancy
- Calcitonin and CEA – particularly relevant when medullary thyroid carcinoma is suspected or diagnosed
- Cross-sectional imaging – CT or MRI when local extent or advanced disease needs further assessment
- Molecular testing – may assist with selected indeterminate nodules and with characterization or treatment selection in advanced disease
Staging
- TNM classification
- Primary tumor extent (
T) - Regional lymph-node involvement (
N) - Distant metastasis status (
M)
- AJCC/UICC stage groups
- Staging and prognostic interpretation differ between major thyroid carcinoma subtypes
Molecular Markers
Relevant markers depend strongly on histological subtype.
- BRAF – particularly associated with papillary thyroid carcinoma
- RET alterations – relevant in papillary thyroid carcinoma and especially medullary thyroid carcinoma
- Germline RET variants – important in hereditary medullary thyroid carcinoma / MEN2
- RAS alterations – found in several follicular-pattern thyroid neoplasms
- NTRK fusions – present in a subset of thyroid carcinomas
- Other actionable molecular alterations may become relevant in advanced or refractory disease
Common Treatments
Treatment depends strongly on histology, disease extent, molecular findings and patient characteristics.
Differentiated Thyroid Carcinoma
- Surgery – primary treatment for many clinically significant differentiated thyroid carcinomas
- Radioactive iodine therapy – used selectively after surgery in iodine-avid differentiated thyroid cancers
- Thyroid hormone / TSH-suppressive therapy
- Active surveillance – an option for selected very low-risk tumors
- Targeted systemic therapy – for selected advanced or radioactive-iodine-refractory disease
- External-beam radiation therapy – used selectively
Medullary Thyroid Carcinoma
- Surgery
- RET-targeted therapy – for eligible advanced RET-altered disease
- Other systemic targeted therapies in advanced disease
- Radioactive iodine is not a treatment for medullary thyroid carcinoma
Anaplastic Thyroid Carcinoma
- Multimodal treatment, depending on resectability and patient condition
- Surgery when feasible in selected cases
- Radiation therapy
- Systemic therapy
- Targeted therapy when an actionable molecular alteration is present
Scope Note
C73 describes primary malignant neoplasms of the thyroid gland. The ICD-10-GM code itself does not distinguish papillary, follicular, medullary, poorly differentiated or anaplastic histology. Histological subtype, molecular characteristics and TNM/UICC stage provide additional clinical characterization outside the C73 code itself.
Benign thyroid nodules, goiter, thyroiditis and other non-malignant thyroid disorders are outside the scope of C73. Malignant tumors that have spread to the thyroid from another primary site should not be represented as primary C73 thyroid cancer.