This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and breast, Subject name: Surgery
Struma ovarii is a 
Select and explain. 
A. Metastatic tumor, B. Teratoma, C. Sex cord tumor, D. Surface epithelial tumor
B: Teratoma
Answer: B: Teratoma 
Explanation: Struma is a river in europe,along its banks endemic goitre was noted. Strauma is loosely used for goitre in europe. A Struma ovarii benign ovarian tumor is a form of teratoma that contains mostly thyroid tissue, which may develop thyrotoxicosis. Source : Bailey and love 26th edition Pg : 748