El carcinoma de tiroides es un tumor infrecuente; constituye menos del 1% de las neoplasias malignas en la población general y el 0, 5%-3% en la edad pediátrica. Existen cuatro tipos: papilar (80%-90% de los casos), folicular (5%-10%), medular (5%) y anaplásico (2%-3%). En el tipo medular, el 80% son esporádicos, y un 20% se asocia a un síndrome hereditario que se divide, fundamentalmente, en tres grupos: neoplasia endócrina múltiple 1, neoplasia endócrina múltiple 2 y carcinoma medular de tiroides familiar. Las formas hereditarias se producen por una mutación en el protooncogén RET, localizado en el brazo largo del cromosoma 10. Se presenta un caso de carcinoma medular de tiroides detectado a raíz de un estudio genético familiar con el propósito de resaltar la importancia del diagnóstico precoz y la intervención de equipos multidisciplinares expertos en esta patología para su manejo y seguimiento. Thyroid cancer is an uncommon type of cancer, accounting less than 1% of all cancers in adults, and 0.5-3% of all cancers in children. There are four different types: papillary carcinoma (80-90% of cases), follicular (5-10%), medullary (5%) and anaplastic cell (2-3%). Eighty per cent of cases of medullary thyroid cancer are sporadic, but 20% are associated with an inherited syndrome that is divided into three groups: multiple endocrine neoplasia type 1, multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma. The inherited forms are caused by a disruption in the RET oncogene, which is located in the long arm of chromosome 10. A hereditary case of medullary thyroid carcinoma is presented. It was detected because of a familial genetic study. The purpose of the paper is emphasize the importance of the early diagnosis and the intervention of multidisciplinary teams of experts.