A 35-year-old woman presents with a non-tender, smooth, fluctuant swelling in the anterior triangle of the neck that transilluminates brilliantly. The swelling has been present since childhood and increases in size during upper respiratory tract infections. The most likely diagnosis is:
- A Cystic hygroma (lymphatic malformation) ✓
- B Branchial cyst — 2nd branchial cleft origin
- C Thyroglossal duct cyst
- D Cervical dermoid cyst
Explanation
Brilliant transillumination is pathognomonic of a cystic hygroma (macrocystic lymphatic malformation), as the multilocular lymph-filled cysts transmit light freely. Characteristically these are congenital, soft, compressible, non-pulsatile, and enlarge dramatically during upper respiratory infections (increased lymphatic flow). Branchial cysts (2nd arch) typically appear in the 2nd–3rd decade along the anterior border of sternocleidomastoid; they do not transilluminate brilliantly. Thyroglossal cysts move on swallowing and tongue protrusion and are midline. Dermoid cysts are solid/doughy without transillumination.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.