Genetic events in the evolution of thyroid cancer

Objective: To delineate the evolution of thyroid cancer using the Volgelstein model of cancer evolution and to demonstrate the genetic hits in the development of undifferentiated cancer from normal thyroid cells. Method: Immunohistochemical and molecular, biologic techniques were used to delineate the prevalence of (1) the ras oncogene, (2) p53, and (3) the ret/PTC oncogene in the development of differentiated thyroid cancer from normal cells and hyperplasia. The evolution of differentiated thyroid cancer to the dedifferentiated or anaplastic type was also investigated. The methodology used was standard immunohistochemical staining techniques as well as polymerase chain reaction technology for the elucidation of these various oncogenes and tumour suppressor genes. Results: We have demonstrated that there is a high preponderance of ras and ret/PTC oncogenes in the evolution of thyroid cancer. Further along the continuum, p53 has been demonstrated to be prevalent in the development of dedifferentiated thyroid cancer (i.e., tall cell and insular variety as well as anaplastic cancer). Conclusion: Several genetic hits have been demonstrated to be prevalent in the evolution of thyroid cancer. These are preliminary oncogenic maps, and further work in this area will help to establish a definite biologic pattern in the development of this malignancy.