<prompt> All of the following ovarian tumours usually occur bilaterally, except :Metastatic massDysgerminomaCyst adenoma of ovaryDermoid cyst  <response>: 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. 