Molecular Diagnosis and Treatment of Multiple Endocrine Neoplasia Type 2B in Ethnic Han Chinese

Background: Multiple endocrine neoplasia type 2B (MEN 2B) is mainly caused by M918T RET germline mutation, and characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO) and non-endocrine features. However, the diagnosis and treatment are usually delayed. Methods: This study reports 5 Chinese pedigrees with 5 individuals harboring germline RET-M918T, and systematically reviewed previous Chinese literature reported. Results: All 5 patients initially presented MTC, but none had biochemically cured postoperatively. 2 also presented bilateral PHEO after adrenal-sparing surgery, 1 needed steroid replacement. Further, a total of 32 MEN 2B patients from literature were clustered with 28 available for analysis. 26 (92.8%) were diagnosed by endocrine-related symptoms; the remaining 2 (7.2%) due to RET testing and oral symptoms, respectively. 25 patients underwent thyroidectomy with/without neck lymph node dissection at the mean age of (23.3 +/- 10.4) years. Histopathological examination revealed MTC ( 100%). Of them, 17 had definite TNM stage, with 1 in stage III and others in IV. Other information of MEN 2B-related symptoms included penetrance of PHEO (60.7%), constipation (32.1%), Hirschsprung disease ( 25%), alacrima (17.8%), mucosal ganglioneuroma (96.4%) and marfanoid habitus (71.4%). 19 patients were verified harboring RET-M918T (c.2753T>C), of whom 15 (78.9%) were de novo mutation. The other 9 were clinically diagnosed as MEN 2B. Discussion & Conclusion: The initial diagnosis of MEN 2B is relatively later, and diagnosed by non-endocrine components is extremely lower. Recognition of MEN 2B and its non-endocrine-related components is still the utmost requirement for a Chinese physician. Combined RET screening and serum calcitonin detection can facilitate early diagnosis.