Adult Cystic Nephroma: Cyst De-roofing as a Parenchyma-sparing Alternative. A Case Report and Review of the Literature

Background. Cystic nephroma is a benign multilocular renal tumour with a bimodal age distribution and fewer than 200 reported cases. In adults it presents almost exclusively in women in the fourth decade, and imaging cannot separate it reliably from a malignant cystic mass, so the lesion is usually classified as Bosniak II or III and treated with total or partial nephrectomy. Case presentation. A 44-year-old woman had six months of colicky left upper quadrant pain with early satiety. Ultrasonography showed a septated cystic structure of 127 x 114 x 96 mm with ipsilateral renal atrophy, and contrast-enhanced computed tomography showed thickened irregular septa with apparent enhancement in a lesion of 92 x 95 x 97 mm (approximately 443 mL), classified as Bosniak IIF/III. At robot-assisted laparoscopy the mass had a high fluid content and few loculi, and the vascular anatomy put the remaining parenchyma at risk during a formal partial nephrectomy. We aspirated the cyst fluid and resected the cyst roof, together with the compartments that resembled intracystic cavities. She was discharged the following day. Histology showed a cyst wall of dense connective tissue with ovarian-type stroma lined by cuboidal epithelium; the stroma expressed oestrogen and progesterone receptors, the epithelium was PAX8-positive, and CAIX was negative, confirming cystic nephroma. Contrast-enhanced computed tomography six months after surgery showed no recurrence. Conclusions. Cyst de-roofing preserved the whole renal unit in a lesion that would conventionally have been treated by nephrectomy. The approach is defensible when imaging shows no solid enhancing component, the cyst is predominantly fluid-filled with few loculi, and the hilar anatomy makes parenchymal resection hazardous, provided histology is obtained and imaging follow-up continues.