F-18 FDG uptake in a retroperitoneal cystic lymphangioma mimicking malignancy.

Retroperitoneal lymphangiomas are rare benign cystic tumors and occur because of failure of the developing lymphatic tissue to establish normal communication with the remainder of the lymphatic system. We present a case of retroperitoneal cystic lymphangioma that mimicked malignancy on FDG PET-CT. Inhomogeneous FDG accumulation was found in this multicystic tumor. Histopathologic findings suggested that lymphocytes in the fibrous septa may contribute to FDG uptake of this retroperitoneal cystic lymphangioma.