Abstract
BACKGROUND: Multiple endocrine neoplasia type 2B (MEN 2B) is a rare hereditary syndrome caused mainly by Met918Thr germline RET mutation and characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO), and typical phenotypic features. MEN 2B cases previously reported in the literature have variable clinical course. OBJECTIVES: We aimed to discuss the characteristics of four MEN 2B cases with unusual presentations,clinical course and review the recent clinical data on MEN2B. RESULTS: All patients had de novo M918T mutation and no family history. The mean age of patients was 38.2 years (27-56). Two patients had typical phenotypic features of MEN 2B; the other two patients had no striking phenotypic features. First detected MEN 2B component was MTC in two, intestinal ganglioneuromatosis in one, and PHEO in one of the cases. Bilateral PHEO was detected in all four cases. CONCLUSIONS: MEN 2B is a complex syndrome characterized by wide phenotypic variability and different clinical outcomes. To diagnose sporadic MEN 2B cases, genetic testing should be performed in all cases with suspicious clinical features. Although early diagnosis is the main factor that increases life expectancy, some MEN 2B patients with late diagnosis may exhibit a mild clinical course and better prognosis than expected, with effective treatment.