Retroperitoneal Castleman disease masquerading as a pancreatic neoplasm: a case report and review of the literature

BACKGROUND: Castleman disease (CD) is a rare lymphoproliferative disorder of unclear etiology, often presenting as an asymptomatic, incidentally detected mass. The predominant pathological variants include hyaline vascular, plasma cell, and mixed types. Clinically, CD is classified into unicentric (UCD) and multicentric (MCD) forms. CASE PRESENTATION: Here we report the case of a 34-year-old Indian female with vague left-sided abdominal pain and bilateral lower limb pain, in whom contrast-enhanced CT revealed an incidental well-defined 5.7 × 3.8 × 3.8 cm mass in the gastrohepatic space, initially suggestive of a pancreatic neuroendocrine tumor or gastrointestinal stromal tumor. However, endoscopic ultrasound-guided biopsy indicated a lymphoproliferative neoplasm. Given the discordant imaging and biopsy findings, surgical resection of the mass was undertaken, and the final histopathology confirmed unicentric Castleman disease. No adjuvant therapy was required, and the patient remains disease-free at 2 years of follow-up. CONCLUSION: This case underscores the favorable prognosis of UCD-complete surgical resection is associated with near 100% long-term survival-and the importance of differentiating such lesions from other retroperitoneal tumors, which are usually malignant. A thorough preoperative evaluation, including an excisional lymph node biopsy or intraoperative frozen section, is recommended to establish the diagnosis and guide management.