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: Pathology
What is Ranne complex? 
Select and explain. 
A. Necrotic material undergoing calciﬁcation, B. The stage is seen in the formation of granuloma, C. Central necrosis surrounded by lymphocytes, D. All of the above
A: Necrotic material undergoing calciﬁcation
Answer: A: Necrotic material undergoing calciﬁcation 
Explanation: The central part of the TB lesion contains caseous, soft, and cheesy necrotic material (caseous necrosis). This necrotic material may undergo calcification at a later stage called Ranne complex, in the lung parenchyma and hilar lymph nodes in few cases.
Key concept:
Necrotic material undergoing calciﬁcation which is seen in TB is known as Ranne complex.
Ref: Shafer's textbook of oral pathology 7th edition page 320