[Medullary cancer of the thyroid: morphological and immunohistochemical definitions. The pathologist's role in 1987].

The morphological and secretories aspects of medullary thyroid carcinomas are reviewed. Mixed follicular and medullary carcinomas are discussed. Criteria for discrimination between sporadic and hereditary forms are mentioned with special reference on C cell hyperplasia. After a brief report on what is known about normal human and animal C cell, a short histogenetic discussion is debated.