This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pathology
[{'content': 'Struma ovaril is composed entirely of \nSelect and explain. \nA. Mature thyroid tissue, B. Immature thyroid tissue, C. Pimary ovarian carcinoid tissue, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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', 'role': 'assistant'}]