Cystic goiter with squamous-cell metaplasia--case report and comment on origin of squamous-cell cyst

A 53-year-old woman with a left unilocular cystic goiter of the size of a small orange was reported. Approximately four-tenths of the innter surface was lined with several layered squamous epithelium with few follicles remaining. A gradual metaplastic transition from the follicular epithelium to the flattened cuboidal and to the squamous epithelium was observed. The ultimobranchial body has been understood to be a possible origin of an entirely squamous cell cyst of the thyroid, three of which have been reported. The difference between the ultimo-branchial and metaplastic origins will be discussed, and a new designation-primary (ultimo-branchial) and secondary (metaplastic) squamous-cell cyst will be proposed.