Thyroid cancers are the most common type of endocrine system tumors and they are treated in endocrinology, nuclear medicine, and general surgery. It shows the most rapid increase among all cancers. While the thyroid cancer held the 14th rank among all cancers in the past, it ranked the 7th in the 2000s.

Thyroid cancers can be classified as follows:

Differentiated thyroid cancers; including papillary cancers, follicular cancers, hurthle cell cancers;

Thyroid medullary cancers,

Anaplastic cancers,

Thyroid lymphoma, and metastatic cancers.

In particular, differentiated thyroid cancers and medullary thyroid cancers often present as nodules. Therefore, it is important to make a differential diagnosis of the nodule.

Sometimes a growing lymph node in the neck or distant organ metastasis may become symptomatic before the primary disease. Thyroid cancer accounts for 5-10% of all thyroid nodules.

In the physical examination; the size, number, and consistency of the nodule should be evaluated; its relationship with the surrounding tissues should be determined, and the size of the lymph node should be measured. Rigid and adherent nodules and the enlarged lymph nodes in the neck suggest malignancy although they may be associated with other potential factors. Pain, dysphagia, hoarseness, difficulties in breathing, and rapid growth of the nodule increase the likelihood of cancer.

The risk of cancer is high in thyroid nodules occurring in children, adolescents, and old individuals. The risk increases up to 40-60% in children receiving radiotherapy to the neck. Thyroid nodules are more common in women but the risk of cancer is 2-3 times higher in men compared to women.

Generally, hormone levels are normal in patients with thyroid cancer. Thyroglobulin, antimicrosomal, and antithyroglobulin antibodies are not important in the differential diagnosis. Calcitonin levels are very important in the diagnosis of medullary thyroid cancer.

Gene groups of RET and TRK protooncogenes have been proposed as the causes of papillary carcinoma. Especially in familial medullary thyroid carcinoma, detection of the mutation in the RET protoncogene on chromosome 10 facilitates the early diagnosis in family members while the disease is still curable.

In a patient with thyroid nodules, the first examination is performed by ultrasound. Important ultrasound examination findings indicating the thyroid cancer include irregular contours, increased vascularity, and microcalcifications. Another characteristic finding than can be visualized in ultrasonography is regional lymphadenomegaly. Needle biopsy is important in the differential diagnosis of thyroid nodules. The results are categorized into five groups as malignant, benign, suspicious, atypia of undetermined significance, and benign.

Adequate surgical treatment is the most important method that affects survival. Treatment should be performed in compliance with the guidelines published by the American Thyroid Society. For this purpose, the patients should be evaluated thoroughly before the surgery and the recommendations of the American Thyroid Society on surgical methods, treatment, and follow-up after the surgery should be followed.

Regardless of the disease stage in differentiated thyroid cancers, excision of the thyroid tissue along with all regional metastases is the first step treatment even in metastatic diseases. Generally accepted mode of treatment is total thyroidectomy. Surgery should be performed by an experienced surgeon to prevent hoarseness (laryngeal nerve damage) and injury in the parathyroid glands. Total thyroidectomy reduces the risk of recurrence and death in all patients. It is the most effective treatment for differentiated thyroid cancer. Levothyroxine therapy is necessary for every patient to prevent the induction of tumor growth by TSH whether or not radioactive treatment has been performed after surgery.

Medullary thyroid cancer is a neuroendocrine tumor that originates from the parafollicular (C cells) cells of the thyroid. It accounts for 2-5% of thyroid cancers. Approximately 25% of medullary thyroid cancers are genetic and familial. The majority of hereditary medullary thyroid cancers may be comorbid with other endocrine diseases. They can be slightly more common in women and they are seen most commonly in 50 to 60 years of age. In medullary thyroid cancer; being 40 years old and older, having cancerous lymph nodes and distant metastases, male gender, an extrathyroidal spread of the disease, high calcitonin levels of > 400 pg, residual tissue after surgery, and persistence of high calcitonin levels indicate poor prognosis.

Genetic testing, ultrasound examinations, assessment of calcitonin levels, and prophylactic total thyroidectomy with central lymph node dissection should be performed in asymptomatic patients having a family history of the disease.

In patients without family medullary thyroid cancer, endocrine diseases such as pheochromocytoma and hyperparathyroidism should be investigated. Total thyroidectomy with central neck dissection is the recommended surgical treatment for the patient with medullary thyroid cancer.

Anaplastic thyroid cancer is a rapidly growing type of thyroid cancer that presents with dysphagia and hoarseness. Even if there are no metastases at the time of diagnosis, systemic treatment should be considered. If possible; surgery, radiotherapy, and chemotherapy should be performed in combination.