This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
A patient presents with pain and cold insensitivity at the fingertip. There is a bluish discoloration under the nail. The most likely diagnosis is? 
Select and explain. 
A. Neurofibroma, B. Glomus tumor, C. Turret tumor, D. Raynaud's disease
B: Glomus tumor
Answer: B: Glomus tumor 
Explanation: Ans. B. Glomus tumorThe giveaway is the bluish colour under the nail. This is typical for the glomus tumor; this is a rare benign neoplasm arising from the glomus body (a neuromyoarterial apparatus). It can be excised by lifting the nail up (if under the nail plate) with repair of the nail bed afterwards.