Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Fetal cystic hygroma ?
    ### Response:
    Fetal cystic hygroma is a congenital malformation of the lymphatic system. The lymphatic system is a network of vessels that maintains fluids in the blood, as well as transports fats and immune system cells. Cystic hygromas are single or multiple cysts found mostly in the neck region.
    