Papillary thyroid carcinoma (PTC) belongs to well-differentiated thyroid cancers. It is the most common of all thyroid cancers and is among the most curable cancers. Clinically, PTC presents as asymptomatic thyroid nodules, it is usually single, firm, freely moveable during swallowing, and it is not distinguishable from a benign nodule. Thyroid nodule should be suspected of being a carcinoma when it is found in children or adolescents or in patients above 60 years, and when there is a history of increase in size. Histologically, PTC is an unencapsulated tumor with papillary and follicular structures. It is characterized by changes in cell nuclei: nuclear overlapping, large sized nuclei, a ground glass appearance, longitudinal nuclear grooves, and invaginations of cytoplasm into the nuclei. The tumor spreads through the lymphatic vessels within the thyroid, to the regional lymph nodes, and less frequently to the lungs. About 10% of papillary carcinomas are completely surrounded by a dense fibrous capsule. Exposure to external radiation to the neck increases the risk of developing thyroid cancer. Intravenous exposure to radiation for medical tests and treatments, however, does not increase the risk of developing thyroid cancer.
The annual incidence rate of PTC in different parts of the world varies from 0.5-10 per 100,000 populations. The tumor most often occurs in individuals aged 20-50 years. In adults, the female-to-male ratio is 3:1; whereas, in children, the tumor is distributed by sex nearly equally. However, females have a better overall prognosis. Papillary thyroid carcinoma occurs more often in whites than in blacks.