Last update:
08-Jul-2004

The thyroid gland contains two major types of epithelial cells, the follicular cells and the parafollicular or C-cells, and the most common thyroid neoplasms arise from these two very different types of cells. Some thyroid tumors simultaneously display morphological and immunohistochemical features of both cell types. The histogenetic origin of these tumors remains unclear. Several hypotheses have been proposed, including the “stem cell theory”, the “divergent differentiation” theory, the “collision effect” theory, the “field effect” hypothesis and the “hostage hypothesis”. In recent years, molecular pathology techniques have been applied to explain the full spectrum of tumors that combine the features of both follicular and parafollicular neoplastic cells, but the possible molecular mechanisms are still far from being well understood.

Key words: Carcinoma, Histogenesis, Thyroid, Thyroid tumors.