MOLECULAR MARKERS AND THYROID CANCER.

Thyroid cancer is the most common malignant tumor of the endocrine system and includes well differentiated forms, namely papillary and follicular carcinomas, and the poorly differentiated and anaplastic carcinomas that result from the transformation of thyroid follicular cells. Notably, 5-10% of all thyroid cancers are medullary thyroid cancers that arise from parafollicular or C cells. The most common genetic mutations in papillary and follicular thyroid cancers are point mutations of the BRAF or RAS genes, while the most common chromosomal alterations are RET/PTC and PAX8/PPAR???rearrangements.The inherited form of medullary thyroid cancer is transmitted as an autosomal dominant trait due to a germline mutation of the RET proto-oncogene, but these mutations occur also in some sporadic cases. The most frequent initial manifestation of thyroid cancer is the appearance of a nodule. In almost all cases, these nodules are benign; in fact, less than 5% are malignant. However, some cases are misdiagnosed, and many patients are subjected to unnecessary surgery. Therefore,, therefore, it is important that patients undergo an accurate pre-surgery evaluation. The most reliable diagnostic test for thyroid nodules is fine needle aspiration cytology, which accurately distinguishes between a benign and malignant lesion in most cases. However, cytological discrimination between malignant and benign follicular cancer is often difficult because of poor quality samples. Here we review the various types of thyroid cancer, the associated point mutations and characteristic gene rearrangements.