An extremely rare case of Rosai-Dorfman disease in the spleen.

Background Rosai-Dorfman disease (RDD) is a rare, multisystemic histiocytic disorder, and commonly manifesting as lymphadenopathy in the young male. Abdominal manifestations of RDD are extremely rare. Case presentation In August 2018, a 42-year-old man underwent an abdominal ultrasonography examination due to his weight loss of 10 kg in only three months and found a giant solid tumor was found in his spleen. Then, he was admitted to our hospital and diagnosed as a splenic mass via abdominal enhanced CT and MRI. Laparoscopic splenectomy was administrated within six days of admission due to the clear surgical indications. The pathogenesis of RDD remained poorly understood and the disease should be diagnosed based on histopathology and immunohistochemistry (IHC). The mutations in ATM and NFKBIA were observed using next generation sequencing (NGS). Conclusion We reported a case of splenic involvement of RDD with NGS genetic testing, indicating the difficulty of making a diagnosis before surgery. This extremely rare case offers new references for the understanding of abdominal viscera RDD.