Renal splenic heterotopia, a rare mimic of renal neoplasia: case report of imaging and fine-needle aspiration biopsy.

Renal splenic heterotopia, a very rare benign occurrence of splenic tissue within the renal capsule, mimics organizing capsular hemorrhage, adenomyolipoma and renal cortical adenoma or carcinoma. It is found incidentally as a result of imaging asymptomatic kidneys for other reasons or may cause signs and symptoms due to mass effect and hypersplenism. When occurring in patients who had had splenectomy it has been classified as splenosis. When found in patients with intact spleens it is called splenorenal fusion and considered to be a developmental heterotopia. Renal splenic heterotopia can be diagnosed by 99mTc-sulfur colloid scan and confirmed with fine needle aspiration biopsy cell block preparations. Unnecessary nephrectomy can be avoided if splenic heterotopia is included in the differential diagnosis of renal lesions, particularly in splenectomized patients.