This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vascular surgery, Subject name: Surgery
A 36yr old lady presents with a 20 yrs duration fluctuant and translucent swelling on right side of her neck. No other history available. No other findings on examination of neck. What is the most probable diagnosis? 
Select and explain. 
A. Lymph cyst, B. Lymph node, C. Colloid nodule, D. Cold abscess
A: Lymph cyst
Answer: A: Lymph cyst 
Explanation: The only swelling of the 4 options which will show translucency is Lymph cyst.Lymph node - no fluctuationColloid nodule - no fluctuationCold abscess - 20-year history unlikely