Unicentric Castleman Disease Presenting with a Ruptured Pseudoaneurysm within the Tumor: A Case Report

INTRODUCTION: Castleman disease is a lymphoproliferative disorder of unknown etiology, typically reported as a hypervascular tumor. Here, we report the first known case of unicentric Castleman disease in which a pseudoaneurysm developed within the tumor and ruptured spontaneously. CASE PRESENTATION: A 55-year-old male was hospitalized due to the sudden onset of epigastric pain. Contrast-enhanced CT revealed a 60-mm hypovascular mass located on the dorsal side of the pancreas, with evidence of extravasation within the tumor. Emergency angiography was performed; nonetheless, the pseudoaneurysm was not clearly identified. The patient was administered antihypertensive therapy and discharged. He was subsequently referred to our hospital for further examination and treatment. Upon reviewing the angiographic images obtained at the previous hospital, a pseudoaneurysm was retrospectively identified in a small branch of the splenic artery. Follow-up contrast-enhanced CT at our hospital showed slight tumor shrinkage and resolution of the extravasation. Although the ventral region of the tumor showed marked enhancement, no noticeable enhancement was observed in the dorsal region. Based on imaging findings, a pancreatic neuroendocrine tumor was suspected. While endoscopic ultrasonography fine-needle tissue acquisition was performed twice, a definitive diagnosis could not be made. Suspecting a pancreatic neuroendocrine tumor, we recommended surgery. The patient underwent anterior radical antegrade modular pancreatosplenectomy. Histopathological findings showed that the tumor had no continuity with the pancreatic tissue and was composed of 2 lesions. The ventral portion of the tumor showed lymphoid tissue proliferation with follicular hyperplasia. Blood vessels traversed the lymphoid follicles, and blood vessel walls showed hyalinization and thickening. No atypical lymphocytes were observed. The dorsal portion of the tumor was necrotic. Based on these findings, the patient was diagnosed with unicentric Castleman disease (hyaline vascular type). At the time of writing, there was no recurrence of the disease 24 months after surgery. CONCLUSIONS: In Castleman disease, as demonstrated in this case, pseudoaneurysm formation may occur. In cases presenting with an intratumoral pseudoaneurysm, Castleman disease should be considered in the differential diagnosis, and angiography should be included for further evaluation and preoperative treatment.