Which is not true about cystic hygroma

Cystic hygroma Cystic hygroma is a swelling usually occurring in the lower third of the neck It is most commonly seen in the posterior triangle of the neck, but may also occur in axilla, groin & mediastinum It results due to sequestration of a poion of the jugular lymph sac from the lymphatic system. It usually manifests in the neonate or in early infancy (occasionally present at bih) The swelling is soft and paially compressible and invariably increases in size when the child coughs or cries. The characteristic that distinguishes it from all other neck swellings is that it is brilliantly translucent. The cysts are filled with clear lymph and are lined by endothelium. Mostly these are multiple cysts but occasionally they can be unilocular. It may show spontaneous regression. "Roughly 50% to 65% of hygromas prsent at bih, with most becoming apparent by the second year of life." Ref : Sabiston 18/e p2052