Struma ovaril is composed entirely of

Struma ovarii is a monodermal or specialised teratoma. They are germ cell tumours of ovary. Struma ovarii is composed entirely of mature thyroid tissue ,which may be functional and causes hypehyroidism. Struma ovarii is a rare ovarian tumor that was first described in 1899. It is defined by the presence of thyroid tissue comprising more than 50% of the overall mass. It most commonly occurs as pa of a teratoma, but may occasionally be encountered with serous or mucinous cystadenomas (Ref : ROBBINS Text book of pathology) REF IMG