Clinical Characteristics and Surgical Outcomes of Retroperitoneal Unicentric Castleman Disease: A Single-Center Retrospective Study

Objective: We aimed to characterize the inflammatory and complication profiles of patients with retroperitoneal unicentric Castleman disease (UCD), compare the clinical features of UCD with an MCD-like inflammatory state (UCD-MIS) and non-MIS cases, and describe treatment patterns and follow-up outcomes. Materials and methods: We retrospectively analyzed 75 patients with retroperitoneal UCD treated at our institution between 2000 and 2025, focusing on inflammatory phenotypes, severe complications, surgical extent, and follow-up outcomes. Results: UCD-MIS was identified in 20 patients (26.7%). Paraneoplastic pemphigus (PNP) occurred in 9 patients (12.0%), bronchiolitis obliterans (BO) in 8 (10.7%), and amyloid A (AA) amyloidosis in 2 (2.7%). Patients with UCD-MIS more frequently had PNP (35.0% vs. 3.6%; FDR-adjusted P = 0.004) and BO (25.0% vs. 5.5%; FDR-adjusted P = 0.042) than those without MIS. For treatment, 61 patients underwent surgery, including 57 complete resections. During a median follow-up of 60.8 months (range, 6.1-266.2 months), two deaths occurred. Both patients had PNP and met the criteria for UCD-MIS, and one also had BO. Neither patient had undergone surgical excision of the UCD lesion. The small number of deaths precluded between-group survival comparisons. Conclusion: Comprehensive screening for complications is essential in retroperitoneal UCD, and complete surgical excision remains the cornerstone of therapy when technically feasible.