Currently, the medical field prefers to use the term lymphatic malformation, because the term cystic hygroma means water tumor. Lymphatic malformation is more commonly used now because it is a sponge-like collection of abnormal growth that contains clear lymphatic fluid. The fluid collects within the cysts or channels, usually in the soft tissue. Cystic hygromas occur when the lymphatic vessels that make up the lymphatic system are not formed properly. The two types of lymphatic malformations are macrocystic (large cysts) and microcystic (small cysts) lymphatic malformations. A person may have only one kind of the malformation or can have a mixture of both macro- and microcysts.