Unicentric Castleman Disease (UCD) is a rare lymphoproliferative disorder typically presenting as a solitary mass, with retroperitoneal cases (<10%) posing diagnostic challenges due to overlap with vascular tumors like paraganglioma . The hyaline vascular (HV) subtype predominates in UCD, lacking the systemic symptoms of multicentric CD . This report details a retroperitoneal UCD near the renal hilum, introducing near-infrared fluorescence (NIRF) imaging with indocyanine green (ICG) as a novel surgical adjunct

A 34-year-old female with six-month right flank pain underwent ultrasound and contrast-enhanced CT (CECT), revealing a 4.8 x 3.3 x 4.8 cm hyperenhancing mass medial to the right kidney, supplied by the lumbar artery. Robot-assisted excision was performed using NIRF-ICG to map vascularity. The mass was dissected from the renal hilum, retrieved via Pfannenstiel incision, and analyzed histopathologically.

Intraoperative NIRF-ICG delineated the lumbar artery supply, enabling precise excision of a 5 x 6 cm mass with 100 mL blood loss over three hours. Histopathology confirmed HV-UCD, showing "onion-skin" follicles and hyalinized vessels. Recovery was uneventful, with discharge on day three and no recurrence at follow-up.

This rare retroperitoneal UCD case underscores diagnostic complexity, often misdiagnosed without histopathology. NIRF-ICG imaging, unreported in prior UCD studies , enhances surgical precision near vascular structures, offering a novel approach to optimize outcomes.