Adult Cystic Nephroma Presenting with Situs Inversus and an Ipsilateral Staghorn Calculus: A Rare Case Report

Background: Adult cystic nephroma is a rare, benign, multiloculated cystic renal neoplasm that predominantly affects perimenopausal and middle-aged women; it belongs to the mixed epithelial and stromal tumor (MEST) family of renal neoplasms according to the World Health Organization classification. Total situs inversus, a congenital mirror-image transposition of the thoraco-abdominal viscera, is itself an uncommon finding, and its coexistence with a renal neoplasm has rarely been documented, with only a small number of comparable cases reported worldwide.

Case presentation: We report a 35-year-old woman with known total situs inversus who was found on cross-sectional imaging to have a large, predominantly cystic, multiloculated right lower-pole renal mass measuring approximately 86.5 × 75.7 × 97.7 mm, together with an ipsilateral staghorn calculus and moderate pelvicalyceal dilatation. Contrast-enhanced CT angiography excluded vascular invasion and confirmed patent, normally opacified renal vasculature with bilateral accessory renal arteries. The patient underwent an uneventful right radical nephrectomy. Gross examination revealed a 10 × 8 × 6 cm multilocular cystic lesion containing a staghorn stone within the renal pelvis. Histopathology showed multiloculated cysts lined by flattened to cuboidal epithelium with intervening fibrous septa composed of bland spindle cells resembling ovarian-type stroma. Immunohistochemistry demonstrated stromal positivity for CD10, estrogen receptor and progesterone receptor. Surgical margins were free of tumor. These findings were diagnostic of adult cystic nephroma, a benign, indolent neoplasm, with no evidence of malignancy.

Conclusion: This case highlights an unusual convergence of two independently rare conditions adult cystic nephroma and total situs inversus in the same patient, complicated further by a coexisting staghorn calculus. It underscores the importance of thorough preoperative vascular and anatomical mapping in patients with situs inversus undergoing renal surgery and adds to the sparse existing literature correlating these two rare entities.