Papillary Thyroid Carcinoma

Abstract

One of the most important roles of thyroid fine needle aspiration (FNA) is the diagnosis of papillary thyroid carcinoma (PTC). PTC is the most common malignancy of the thyroid, representing approximately 60–80% of thyroid malignancies. PTC occurs more often in women, and although it can occur at any age, even in childhood, the peak incidence is in patients between 30 and 50 years of age. PTC typically has an indolent clinical course and can be cured by thyroidectomy and radioactive iodine therapy, even if metastatic. Because of these therapeutic implications, an accurate FNA diagnosis is essential. When metastatic, PTC spreads to regional cervical lymph nodes that drain the thyroid gland. Consequently, FNA can also be used to monitor patients for recurrence of PTC. An array of PTC variants are recognized, and some, such as the tall cell variant, columnar cell variant, and diffuse sclerosing variant, can display a more aggressive clinical course and may even develop resistance to radioactive iodine therapy. The molecular mechanisms for PTC development are not well understood, but often involve chromosomal translocations of the RET proto-oncogene and abnormal cell growth stimulated by mutations in genes such as NRAS or BRAF. In addition, there is growing evidence that PTCs that harbor a BRAF mutation may have a higher risk of recurrence than those without BRAF mutations.