Thyroid Cancer: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Thyroid cancer is the most common endocrine malignancy, with approximately 586,000 new cases globally per year. Four main histological types: papillary thyroid carcinoma (PTC, ~85%), follicular (FTC, ~10%), medullary (MTC, ~2-3%), and anaplastic (ATC, <1%). Incidence has risen markedly due to incidental detection on cross-sectional imaging.

Prior ionizing radiation to the neck (especially in childhood) is the strongest risk factor for PTC and FTC. Iodine deficiency promotes FTC. Key molecular drivers: BRAF V600E (~60% of PTC, associated with worse prognosis), RET/PTC rearrangements (PTC), RET point mutations (MTC: somatic or germline in MEN2A/2B), RAS mutations (FTC), and TP53/TERT promoter mutations (ATC, poorly differentiated).

Asymptomatic thyroid nodule discovered incidentally is the most common presentation. Neck mass, dysphagia, hoarseness (recurrent laryngeal nerve invasion), stridor, and cervical lymphadenopathy in locally advanced disease. Medullary TC: diarrhea (calcitonin excess), facial flushing, Cushing's syndrome (ectopic ACTH). Anaplastic TC: rapidly enlarging painful neck mass with compressive symptoms developing over weeks.

Thyroid ultrasound for nodule characterization (TIRADS classification). Ultrasound-guided FNA cytology (Bethesda System I-VI guides management). Serum TSH and thyroglobulin. Calcitonin and CEA for medullary TC; RET mutation testing (germline and somatic). BRAF V600E, RAS, TERT promoter mutations for risk stratification. Post-thyroidectomy: radioactive iodine (RAI) whole body scan.

PTC/FTC: total thyroidectomy for tumors >4 cm or high-risk features; hemithyroidectomy for low-risk <4 cm. RAI (iodine-131) ablation for high-risk differentiated thyroid cancer. TSH suppression with levothyroxine. MTC: total thyroidectomy plus central neck dissection; RET-mutated advanced disease: selpercatinib (FDA-approved); wild-type: cabozantinib or vandetanib. ATC with BRAF V600E (25-40%): dabrafenib plus trametinib — highly effective. Lenvatinib for RAI-refractory differentiated TC.

PTC Stage I/II: 5-year OS essentially 100%. Stage III/IV differentiated TC: 5-year OS approximately 50-85%. MTC with distant metastasis: 10-year OS approximately 25%. ATC: historically median OS 3-5 months; BRAF V600E-positive ATC treated with dabrafenib plus trametinib shows objective response rates of approximately 56% with some durable responses, dramatically improving from historical outcomes.