ONE OF the unusual and fascinating oddities of pathology is the occurrence in an ovarian tumor of any of a great number of tissues or organs. These tumors are generally referred to as dermoid cysts, but, as Blackwell and his coworkers have pointed out, more properly should be known as cystic teratomas. These authors and others * have discussed the etiology of these tumors and described the great variations in their composition. One such type of teratoma is made up, in part or completely, of thyroid tissue, and is called struma ovarii.
In 1952 Sanders9 estimated that there were approximately 180 reports of struma ovarii in the literature. In only about 17% of cases is the tissue entirely thyroid, without other elements of a teratoma.3 In Blackwell's series of 100 cystic teratomas, 13% contained some thyroid tissue. As only about 5% of ovarian neoplasms are cystic teratomas, it follows that struma ovarii with other