Carcinoma of the thyroid

Abstract

Thyroid cancer is the most rapidly increasing malignancy in the US. Thyroid cancer accounts for 1.5% of all malignancies in the US and it is the most common endocrine malignancy - acounting for over 95% of endocrine malignancies. Over 56,000 new cases are diagnosed annually in the US, 74% in females, and it is the most rapidly increasing cancer in incidence. Despite its low malignant potential, every year, approximately 2290 patients die of thyroid cancer in the US. Thyroid cancer is the 5th most common cancer in women; it is only surpassed by breast, lung, colon, and uterine cancer. The diagnosis of thyroid cancer has evovled over the years. The common presentation in the past was of a palpable thyroid nodule while today most thyroid nodules are smaller, nonpalpapble, and are usually identified on neck imaging. The most important diagnostic tool for the evaluation of thyroid nodule is the fine needle aspiration biopsy. When performed under the ultrasound guidance, a non-palpable thyroid nodule can be aspirated and evaluated by cytology with a specificity of over 97% for malignant samples. Thyroid cancers are traditionally divided into four types that are based on their cell origin. The two most common types of thyroid cancer are papillary and follicular thyroid cancers that originate from the follicular cells. These two types are considered well differentiated thyroid cancers and mostly carry a very good prognosis. In contrast medullary and anaplastic thyroid cancers are considered poorly differentiated thyroid cancers with a corresponding worst prognosis. Medullary thyroid cancer is a neuroendocrine tumor of the parafollicular or C cells of the thyroid gland and anaplastic thyroid cancers are undifferentiated tumors of the thyroid follicular epithelium. The purpose of this review is to elaborate on the principles for diagnosis of thyroid cancer and to detail the differences between the four types of thyroid cancers. The diagnosis, epidemiology, pathogenesis, management, and prognosis of each thyroid cancer type will be explained and reviewed in detail. © 2013 Nova Science Publishers, Inc. All rights reserved.