INTRODUCTION: Castleman's disease (CD) refers to scarce lymphovascular hyperplasia categorized as unicentric (UCD) or multicentric (MCD). Retroperitoneal UCD is uncommon (6.7 %) and frequently grows undetected, making diagnosis challenging. The hypervascular nature of hyaline-vascular variant and the average larger size of UCD may result in complete resection difficulty. We present a case of large pelvic UCD completely resected without previous prophylactic procedures or massive intraoperative bleeding with coexisting cholecystolithiasis, which follows the SCARE 2023 guidelines. CASE PRESENTATION: A 45-year-old male was accidentally observed with pelvic mass suppressing ureter and right internal iliac artery in preoperative MRI for cholecystolithiasis and cholecystitis. Epigastric pain, vomiting, and jaundice due to the inflamed gallbladder had resolved before mass removal. Biopsy and immunohistochemistry (IHC) tests confirmed the hyaline-vascular CD. Complete resection per laparotomy was done due to lesion adherence and identified a 7x5x2.5 cm solid mass with cystic degeneration suppressing the ureter. After five months, the patient fully recovered with no symptoms. DISCUSSION: Asymptomatic mass presented as lymphadenopathy on imaging should suggest CD. A prompt lymph node biopsy followed by a pre- or postoperative IHC test is important in diagnosing CD. Total pelvic mass excision with rectum preservation is feasible for larger (>
5 cm) hypervascularized masses without remarkable bleeding and promotes recovery without adjunctive treatments. CONCLUSION: Complete excision per laparotomy is accessible for the uncommon large pelvic retroperitoneal UCD-suppressing ureter.