Researchers from Japan reported the case of 4 patients with medullary thyroid carcinoma (MTC) as part of multiple endocrine neoplasia in the same family. The study was published in the journal Molecular and Clinical Oncology

The finding underscores the importance of screening and taking a detailed family history in patients with medullary thyroid carcinoma, the authors wrote. Most cases of MTC are associated with mutations in the RET gene.

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The first patient reported in this study was a 19-year-old man who had MTC with lung metastases. When he was tested genetically, it became apparent that he had a RET codon M918T mutation, which indicated multiple endocrine neoplasia type 2B (MEN2B). 

The second case was the mother of the patient who had undergone total thyroidectomy at age 12 when she was diagnosed with MTC‑related MEN2B. However, she was not counseled properly and did not know the genetic characteristics of MEN2B. 

The other 2 cases were those of her 2 other children. They were assessed after their brother was diagnosed and were found to have the same mutation. One child had MTC and was treated with total thyroidectomy. The other also underwent total thyroidectomy even though she was asymptomatic at the time.

“Genetic counseling is essential in treating MEN2B,” the researchers concluded. They said that had the mother been informed about the genetic characteristics of MEN2, MTC could have been achieved in her children more quickly. 

The RET germline mutations associated with MEN2 are inherited in an autosomal dominant manner. The M918T RET mutation associated with MEN2B is seen in 95% of patients. There are also other mutations that are much rarer that can be associated with MEN2B.  


Tanaka A, Uemura H, Morimoto C, et al. Four cases of medullary thyroid carcinomas associated with multiple endocrine neoplasia 2B with rearranged during transfection codon M918T mutation in the same family. Mol Clin Oncol. 2022;16(1):13. doi:10.3892/mco.2021.2450