C51-22 A Fatal ‘Sepsis’: Intravascular Large B-cell Lymphoma in Disguise

Abstract Introduction Intravascular large B-cell lymphoma (IVLBCL) is a rare, aggressive subtype of non-Hodgkin lymphoma characterized by selective proliferation of neoplastic cells within small vessel lumina. Cases in Western countries more commonly involve the central nervous system or skin, whereas patients in Eastern regions often present with hemophagocytic syndrome or medullary disease. The absence of lymphadenopathy, low circulating tumor burden, and subtlety of morphologic clues contribute to delays in diagnosis. By presentation, most have advanced disease, and a substantial proportion are diagnosed only at autopsy. We report a unique case with mixed features who manifested respiratory involvement and ultimately suffered cardiovascular collapse. Case Presentation A 55-year-old man with six months of fatigue and unintentional weight loss presented with progressive dyspnea and cough. Laboratory results revealed mild thrombocytopenia with elevated D-dimer, but imaging was negative for pulmonary embolism. There were ground-glass opacities concerning for early pneumonia and splenomegaly up to 17 cm. He tested positive for COVID, received fluids, and was discharged from the Emergency Department. His symptoms worsened with associated fevers and altered mentation, prompting hospital admission two weeks later. He was treated for sepsis of unclear source with empiric antibiotics and steroids without improvement. Follow up imaging showed further enlargement of the spleen to 24 cm, now with wedge-shaped parenchymal hypodensity consistent with infarct, but no significant lymphadenopathy. He acutely decompensated with escalating oxygen needs and was transferred to the intensive care unit, where he suffered a PEA cardiac arrest. He died despite prolonged resuscitative efforts. Autopsy revealed a markedly enlarged spleen, weighing 3 kg, ten times the size of normal. Immunohistochemistry demonstrated diffuse large B-cell lymphoma with extensive intravascular involvement across sampled organs, presumably causing respiratory failure through pulmonary vascular infiltration. Discussion This case highlights how IVLBCL may mimic a routine infectious pulmonary process with unrevealing early diagnostics. Rapid clinical decline and lack of an optimal biopsy target make timely diagnosis and therapy difficult. Cutaneous variants grant an earlier opportunity for biopsy and therefore carry a better prognosis, but diagnosis can still often be delayed. Therefore, in patients with splenomegaly without localized lymphadenopathy and lack of response to standard infectious therapies, suspicion should be raised for an underlying hematologic malignancy. This abstract is funded by: None