Retroperitoneal lymphangioma. 

A lymphangioma is a benign proliferation of lymph vessels, producing fluid-filled cysts that result from a blockage of the lymphatic system. The incidence of abdominal lymphangiomas is unknown.

Retroperitoneal lymphangiomas account for nearly 1% of all lymphangiomas and are uncommon incidental findings usually at surgery, autopsy or lymphography. These may be capillary, cystic or cavernous, with a uniseptate or multiseptate appearance. Although retroperitoneal lymphangiomas may sometimes be asymptomatic, they usually present as a palpable abdominal mass and are easily confused with other retroperitoneal cystic tumors including those arising from the liver, kidney and pancreas. They may become symptomatic if they become large enough to impose on surrounding structures.

These rare tumors have an excellent prognosis, with symptomatic relief and cure achieved with complete surgical excision.

A cystic retroperitoneal lesion can carry a relatively broad differential which includes:

• cystic lymphangioma
• mucinous cystadenoma
• cystic teratoma
• cystic mesothelioma
• pseudomyxoma retroperitonei with cystic change
• perianal mucinous carcinoma with cystic change
• retroperitoneal hematoma with liquefaction
• retroperitoneal hydatid cyst.
• retroperitoneal bronchogenic cyst.