malignancy          
noun  medical specialized uk/məˈlɪɡ.nən.si/ us/məˈlɪɡ.nən.si/
 [ U ]恶性;恶意 
the state of being malignant
  The malignancy of these tumours makes them difficult to treat. 这些肿瘤为恶性,很难治疗。 
  [ C ]恶性生长,恶性肿瘤 
a growth that is likely to get worse and lead to death
  Tests revealed a malignancy that had to be removed. 检查发现了一个恶性肿瘤,必须切除。