Thyroid cancer is the most common endocrine malignancy and an important global health concern. According to GLOBOCAN 2022, approximately 821,214 new cases were reported worldwide. Despite its increasing incidence, mortality remains relatively low because most cases are differentiated tumors with favorable outcomes. The main types include papillary, follicular, oncocytic, medullary, and anaplastic thyroid carcinoma. Diagnosis involves clinical examination, serum thyroid-stimulating hormone (TSH) measurement, ultrasonography, and fine-needle aspiration cytology. Treatment depends on tumor type, size, stage, and recurrence risk. Surgery remains the primary treatment for most patients, while radioactive iodine, thyroid hormone therapy, active surveillance, and targeted therapies are used selectively. The 2025 American Thyroid Association (ATA) guidelines emphasize individualized management and less extensive surgery for selected low-risk tumors. This article reviews the epidemiology, risk factors, diagnosis, and current management of thyroid cancer. Keywords: Thyroid cancer, thyroid carcinoma, thyroid nodules, diagnosis, thyroidectomy, radioactive iodine, targeted therapy. 1. Introduction Thyroid cancer develops from malignant transformation of thyroid follicular or parafollicular cells. It occurs more frequently in females and can affect individuals of different ages. Most cases are differentiated thyroid cancers that grow slowly and have an excellent prognosis, although some types are aggressive and require intensive treatment. 2. Epidemiology In 2022, approximately 821,214 new cases and 47,507 deaths from thyroid cancer were reported worldwide. The disease ranked seventh in global cancer incidence, with approximately 72.6% of cases occurring in Asia. Its increasing incidence is partly attributed to improved detection of small tumors through ultrasound and other imaging techniques, raising concerns about overdiagnosis and unnecessary treatment. 3. Risk Factors Major risk factors include childhood exposure to ionizing radiation, family history of thyroid cancer, and inherited genetic syndromes. Medullary thyroid carcinoma may be associated with mutations in the RET gene and multiple endocrine neoplasia type 2. Other molecular alterations, including BRAF and RAS mutations, contribute to thyroid tumor development and progression. 4. Classification Thyroid cancer is classified into three main groups: • Differentiated thyroid carcinoma: Includes papillary, follicular, and oncocytic carcinoma. Papillary carcinoma is the most common type and frequently spreads to cervical lymph nodes, whereas follicular carcinoma may spread through the bloodstream to the lungs and bones. • Medullary thyroid carcinoma: Arises from parafollicular C cells, which produce calcitonin, and may have a hereditary origin. • Anaplastic thyroid carcinoma: A rare, highly aggressive tumor associated with a poor prognosis. 5. Clinical Presentation and Diagnosis Thyroid cancer commonly presents as a thyroid nodule detected during physical examination or medical imaging. Other manifestations may include enlarged cervical lymph nodes, neck discomfort, difficulty swallowing, breathing difficulties, or hoarseness, particularly in advanced disease. Diagnosis typically involves clinical examination, serum TSH measurement, and high-resolution thyroid ultrasonography. Ultrasound evaluates nodule size, composition, margins, echogenicity, calcifications, and cervical lymph nodes. Fine-needle aspiration cytology is performed when clinical or ultrasound findings indicate a need for further investigation. Molecular testing may also help evaluate selected nodules with indeterminate cytology. 6. Management and Treatment Treatment is individualized according to tumor characteristics, disease stage, recurrence risk, and patient preferences. Surgery is the primary treatment for many differentiated thyroid cancers.According to the 2025 ATA guidelines, thyroid lobectomy may be sufficient for selected low-risk tumors measuring 2 cm or less, provided there is no extrathyroidal extension or cervical lymph-node metastasis. For selected tumors larger than 2 cm and up to 4 cm, either lobectomy or total thyroidectomy may be appropriate. Active surveillance is an alternative for carefully selected small, low-risk cancers. It involves regular monitoring to identify tumor growth or other signs of progression while avoiding unnecessary surgery. Radioactive iodine (RAI) therapy may be used after surgery in selected patients, particularly those with higher-risk disease or iodine-avid residual or metastatic tumors. Thyroid hormone therapy, usually with levothyroxine, replaces thyroid hormone following thyroidectomy and may be adjusted to maintain an appropriate TSH level according to recurrence risk. Targeted therapy may be considered for advanced differentiated thyroid cancer that progresses despite treatment and becomes radioactive-iodine refractory. Molecular testing helps identify patients who may benefit from specific treatments. Medullary and anaplastic thyroid cancers require specialized multidisciplinary care, and genetic evaluation is important when hereditary medullary carcinoma is suspected. 7. Prognosis and Follow-up Prognosis depends on tumor type, age, stage, local invasion, lymph-node involvement, distant metastasis, and response to treatment. Differentiated thyroid cancer generally has an excellent prognosis, especially when diagnosed early. Follow-up may include clinical examination, neck ultrasonography, serum thyroglobulin, and anti-thyroglobulin antibody measurements. The 2025 ATA guidelines emphasize ongoing reassessment of recurrence risk based on the patient’s response to treatment. 8. Conclusion Thyroid cancer is a common endocrine malignancy with diverse clinical behavior. Early diagnosis and accurate risk assessment are essential for selecting appropriate treatment and avoiding unnecessary interventions. Surgery remains central to management, while active surveillance, radioactive iodine, thyroid hormone therapy, and targeted treatments have important roles in selected cases. Current guidelines emphasize individualized care, shared decision-making, and reduced treatment intensity for low-risk disease. Advances in molecular diagnostics and targeted therapies continue to improve treatment options, particularly for advanced thyroid cancer. References 1. Ringel MD, Sosa JA, et al. 2025 American Thyroid Association management guidelines for adult patients with differentiated thyroid cancer. Thyroid. 2025;35(8):841–985. doi:10.1177/10507256251363120. 2. International Agency for Research on Cancer. Global Cancer Observatory: Cancer Today. Lyon: IARC; 2024. 3. Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2016;26(1):1–133. 4. Filetti S, Durante C, Hartl D, et al. Thyroid cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2019;30(12):1856–1883. 5. WHO Classification of Tumours Editorial Board. Endocrine and Neuroendocrine Tumours. 5th ed. Lyon: IARC; 2022. 6. 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