Medullary thyroid cancer: epidemiology

Abstract

Epidemiology of medullary thyroid cancer is presented in the literature review. Thyroid cancer is the most common form of endocrine oncological pathology. It accounts for 96–97 % of all malignant tumors of endocrine organs. According to the Surveillance, Epidemiology, and End Results Program (USA), the incidence of thyroid cancer in 1975–2009 increased approximately threefold, from 4.9 to 14.3 cases per 100,000 population. At the same time, the mortality rate remained low, approximately at the same level, 0.5 cases per 100,000. Such a situation can be explained to some extent by the improvement of diagnostic capabilities of the early, often preclinical, stage of thyroid tumors. Medullary thyroid cancer ranks third after papillary and follicular cancer, but surpasses them in terms of aggressiveness. It is a re­latively rare disease. This type of tumor makes up 1–9 % of all thyroid cancers. Against the background of the general tendency to increase the incidence of thyroid cancer, the absolute number of cases of medullary cancer according to various data remains relatively stable. Epidemiological characteristics of medullary thyroid cancer deserve attention in the age aspect, as well as when considering the frequency of detecting these tumors at autopsy of people who had no signs during their lifetime. In clinical practice, medullary thyroid cancer occurs in two main forms — sporadic and hereditary. The latter is represented as part of the combined syndrome of multiple endocrine neoplasia type 2 (MEN-2), which, in turn, is divided into two subtypes: MEN-2A and MEN-2B syndromes. MEN-2 syndrome is a rare combined hereditary pathology. Sporadic medullary thyroid cancer accounts for approximately 70–80 % of such tumors. It is accompanied by other types of endocrinopathies. Most cases of medullary thyroid cancer occur in the fifth decade of life. The presented data on the epidemiology of medullary thyroid cancer allow for a more detailed and in-depth study of this pathology and contain a certain amount of useful and necessary information.