This case was diagnosed since 2 and half years of having a retroperitoneal abdominopelvic cystic lesion that was considered mostly lymphangioma based on imaging features and performed aspiration that partially decreased lesion size. Now, the size of the lesion progressed with preserved same radiological features.

The diagnosis of retroperitoneal lymphangioma was made upon the creeping behavior of the lesion that appears multicystic of homogenous density with no post-contrast enhancement. It smoothly wraps the left kidney and adrenal gland gently displaces bowel loops and other abdominal structures with a line of cleavage from all surroundings. It is abutting vascular structures with no vascular compromise. All these features are representative of a benign slowly growing retroperitoneal cystic mass lesion which makes lymphangioma the most likely diagnosis.

Retroperitoneal lymphangioma is a rare slowly growing benign proliferation of lymph vessels. It accounts for nearly 1% of all lymphangiomas, the majority are at the head and neck (>95%). It is uncommon incidental findings usually at surgery, autopsy or lymphography. They may sometimes be asymptomatic or 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. Complete surgical excision is the treatment of choice. Definitive diagnosis is only by pathological examination.