Molecular defects in thyroid carcinomas: role of the RET oncogene in thyroid neoplastic transformation.

Tumors are believed to arise as a result of an accumulation of mutations in critical genes involved in the control of cell proliferation. Thyroid neoplasms represent a good model for studying the role of these mutations in epithelial cell multistep carcinogenesis because they comprise a broad spectrum of lesions with different degrees of malignancy. Recent reports have described the involvement of specific genetic alterations in different types of thyroid neoplasms. Papillary carcinomas are characterized by the activation of the receptor tyrosine kinases RET and TRK-A proto-oncogenes. Ras point mutations are frequently observed in tumors with follicular histology and a high prevalence of p53 point mutations have been found in anaplastic carcinomas. A definition of molecular defects characterizing thyroid tumors will be helpful in establishing sensitive and specific detection strategies and, in addition, to define genetic and environmental factors important for their pathogenesis.