A rare collision tumor of paraganglioma and intravascular large B-cell lymphoma: a case report and literature review.

Intravascular large B-cell lymphoma (IVLBCL) is a rare and aggressive subtype of extranodal diffuse large B-cell lymphoma. It is characterized by the selective proliferation of lymphoma cells within the lumina of small blood vessels. Collision tumors involving IVLBCL are exceedingly rare, and no cases involving paraganglioma as a collision component have been reported to date. We report the case of an 80-year-old man who presented with nonspecific gastrointestinal symptoms and intermittent fever. Imaging studies suggested biliary and intra-abdominal malignancies. Surgical resection revealed a mesenteric mass. Histopathological examination demonstrated features consistent with paraganglioma. Notably, numerous atypical lymphoid cells were identified within the lumina of small vessels in the tumor. Immunohistochemical analysis showed positivity for CD20, CD19, PAX5, MUM1, and BCL2, supporting a diagnosis of IVLBCL. Epstein-Barr virus-encoded RNA (EBER) in situ hybridization was negative. Systemic involvement was excluded based on clinical evaluation and imaging findings. The final diagnosis was IVLBCL in collision with paraganglioma. Given the patient's advanced age and poor performance status, intensive chemotherapy was considered unsuitable, and targeted therapy with 'Surufatinib' was initiated. During follow-up, no recurrence of the primary tumor was observed. However, the patient subsequently developed duodenal adenocarcinoma and received appropriate treatment. The patient died approximately two years after the initial diagnosis. To the best of our knowledge, based on a systematic literature search in PubMed up to April 2026, this is the first reported case of a collision tumor composed of paraganglioma and IVLBCL. This case underscores the diagnostic challenges of IVLBCL due to its nonspecific presentation and its potential to be overlooked when coexisting with other tumors. Careful histopathological evaluation, particularly of intravascular components, is essential for accurate diagnosis. Increased awareness may facilitate early detection and improve patient outcomes.