Cystic Nephroma of the Kidney

Abstract

A 65-year-old female presented to the emergency room with shortness of breath. Chest computerized tomography revealed a pulmonary embolus as well as, a large, complex cystic lesion of the left kidney. Followup imaging confirmed a 16 cm Bosniak III cystic lesion. After reviewing management options, the patient elected laparoscopic radical nephrectomy. Gross examination revealed a 13 cm complex, multiloculated cystic lesion. Microscopic examination showed a well circumscribed lesion composed of cysts of variable size. The cysts were separated by septae with variegated appearance containing fibrous areas, calcified material, ovarian like stroma and histiocytes (fig. 1). Immunostain for estrogen receptor (ER) was diffusely and strongly positive in the areas of ovarian like stroma (fig. 2). No solid areas or clusters of clear cells in the septae were seen. The final diagnosis was cystic nephroma (CN). The World Health Organization defines cystic nephroma as a benign cystic neoplasm of the kidney with cysts lined by a single layer of flattened, low cuboidal or hobnail epithelium and separated by fibrous septa with scant cellularity or cells