Cystic lymphatic malformation of bladder presenting as a pelvic mass.

We report a 5-year-old boy with a cystic lymphatic malformation (LM) of bladder, and the imaging characteristics of the lesion are reported. Cystic LM of the urinary system is rare, and a location in the bladder is extremely rare. The exact mechanism of the lesion that occurs in bladder is unknown. This case is different from the 3 cases reported before, for it is only presented with a palpable pelvic mass and the lesion did not penetrate full thickness of bladder. Although imaging examinations are helpful in the definition of cystic LMs, no characteristic findings are available to diagnose a cystic LM of the bladder before surgery. The diagnosis is always made after surgical intervention. Surgical excision is ideal, and an extensive operation is not warranted because the lesion is benign. Once excised completely, the prognosis of the disease is good.