New presentation of familial medullary thyroid carcinoma in 87-year-old patient with high-risk RET proto-oncogene codon 620 mutation.

Objective: We report a case of familial medullary thyroid carcinoma in an 87-year-old woman, despite the patient having a high-risk codon 620 mutation.

Method: Medline and PubMed were searched for cases and literature reviews relating to the following keywords: 'codon 620', 'medullary thyroid carcinoma', 'multiple endocrine neoplasia' and 'RET proto-oncogene'.

Results: We report the case of an 87-year-old woman who presented with a goitre, later identified as medullary thyroid carcinoma. Genetic analysis revealed a RET proto-oncogene codon 620 mutation. Genetic testing has revolutionised the management of medullary thyroid carcinoma. The genetic basis of hereditary medullary thyroid carcinoma lies with the RET proto-oncogene. Several disease-causing mutations of this gene have been identified and their clinical prognosis described. The penetrance of these mutations is high; as such, carriers progress to develop medullary thyroid carcinoma at a young age. Mutations at the codon 620 position are classified as high-risk for early development of medullary thyroid carcinoma; thus, the current recommendation is for prophylactic thyroidectomy at five years of age.

Conclusions: In this case, the progress of hereditary medullary thyroid carcinoma was unique, considering the late presentation of medullary thyroid carcinoma despite the presence of the high-risk RET proto-oncogene codon 620 mutation. The authors wish to highlight the importance of this case, as it may present a counter-argument to the current recommendations for early, prophylactic thyroidectomy in codon 620 mutation carriers in order to prevent early development of medullary thyroid carcinoma.