Cyst of the thyroglossal duct results from a developmental anomaly of the thyroid gland. There are many congenital neck masses only outnumbered by benign lymphadenopathies. The majority appear in children between 2 und 10 year-old, but nearly a third of cases does not manifest clinically until much later (20 year or so). In association to a carcinoma is an uncommon event, but there are published malignant cases. The AA. report the case of a 74-year-old patient with a neck cystic mass evolving during a 40-year-term associated to a laryngeal squamous carcinoma. The imagery shows the radiological and anatomopathological correlation of changes in the tissues interpreted as a cyst of thyroglossal duct and a squamous carcinoma of the larynx, independent of each other.