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What is Brilliantly translucent swelling in the neck region in a 2 year old child, diagnosis is and explain in detail?
CYSTIC HYGROMA:
• Cystic hygromas are multiloculated cystic spaces lined by endothelial cells.
• It results due to sequestration of a portion of the jugular lymph sac from the lymphatic system.
• Cysts are filled with clear lymph and are lined by endothelium.
• Turner's syndrome is associated with cystic hygroma.
• Most cystic hygromas involve the lymphatic jugular sacs.
• MC site: Posterior neck region.
• Other common sites: Axilla, mediastinum, inguinal and retroperitoneal regions.
• Approximately 50% of them are present at birth.
• It may show spontaneous regression.
Clinical Features
• Usually present as soft cystic masses. that distort the surrounding anatomy, can result in acute airway obstruction.
• Usually manifests in the neonates or in early infancy (50% present at birth).
• Prone to infection and hemorrhage within the mass.
• Swelling is soft and partially compressible and invariably increases in size, when the child coughs or cries.
• Characteristic features: Brilliantly translucent.
Diagnosis 
• MRI play a crucial role in preoperative planning.
Treatment 
• Complete surgical excision is the preferred treatment.
• Injection of sclerosing agents, such as bleomycin or OK-432 (Picibanil), derived from Streptococcus pyogenes may eradicate the cystic hygroma.