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
Choriocarcinoma is differentiated from invasive mole (chorio-adenoma destruens) by: 
Select and explain. 
A. Presence of high titre of urinary chorionic gonadotrophin, B. Presence of cannon ball shadow in the lungs, C. Absence of villi structure on histological examination of the lesion, D. All of the above
C: Absence of villi structure on histological examination of the lesion
Answer: C: Absence of villi structure on histological examination of the lesion 
Explanation: Choriocarcinoma is characterised by absence of villi
High titre of urinary chorionic gonadotrophin and cannon ball shadow in the X-ray lungs are found in both choriocarcinoma and invasive mole.