This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Medical, surgical and gynaecological illness complicating pregnancy, Subject name: Gynaecology & Obstetrics
Which of the following ovarian tumour is most prone to undergo torsion during pregnancy ? 
Select and explain. 
A. Serous cystadenoma, B. Mucinous cystadenoma, C. Dermoid cyst, D. Theca lutein cyst
C: Dermoid cyst
Answer: C: Dermoid cyst 
Explanation: Dermoid cyst is most prone to undergo tiorsion in pregnancy. Refer page no 224 for the question AIIMS 2006 , Text book of obsteritics,sheila balakrishnan,2 nd edition. Because ofmthe high incidence of mucinous cystadenomas, dermoid cyst torsion is most frequently seen with these tumours. There is no paicular age incidence. The right and left sides are involved with equal frequency. Usually, the tumour rotates so that its anterior surface turns towards the patient's right side. It is not uncommon for the tumour to be rotated through three or more complete circles. As a result of rotation, the veins in the pedicle become occluded, the tumour becomes congested, and there is interstitial haemorrhage in the wall of the tumour and into the loculi. The increased tension causes severe abdominal pain and the signs of peritoneal irritation. Reference: Shaw's Textbook of Gynaecology 16th edition page 445