This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
All of the following ovarian tumours usually occur bilaterally, except : 
Select and explain. 
A. Metastatic mass, B. Dysgerminoma, C. Cyst adenoma of ovary, D. Dermoid cyst
D: Dermoid cyst
Answer: D: Dermoid cyst 
Explanation: Ans. is d i.e. Dermoid cyst "Dysgerminomas are the only germ cell malignancy with a significant rate of bilateral involvement 15 to 20%. Remember : A "Funda"-- Germ cell tumours are unilateral and maximum bilaterality is seen in dysgerminoma amongst germ cell tumour and that too only in 15 - 20% cases. So, the other germ cell tumor will obivously be less bilateral therefore our answer is dermoid cyst.