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: ENT
[{'content': 'Juvenile nasopharyngeal angiofibroma spreading to pterygomaxillary fossa is which stage? \nSelect and explain. \nA. Stage I, B. Stage II, C. Stage III, D. Stage IV', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is .b, i.e., Stage IIlRef: Neuroradiologlt by Zimmerman p. 455; CT and MRI of the Whole Boily Shle p' 6101IA -+ Tumor limited to posterior nares or nasopharyngeal vaultIB + Extension into one or more Paranasal sinusesIIA -+ Minimal lateral extension through sphenopalatine foramen into medial pterygomaxillary fossa.IIB + Full occupation of pterygomaxillary fossa, di-splacing posterior wall of antrum forward; superior extension eroding orbital bones.IIC + Extension tt roogi ptetygomoilary fossa into cheek and temporal fossaIII -+ Intracranial extension", 'role': 'assistant'}]