Localized lymphoid hyperplasia of the spleen: a rare benign condition grossly mimicking malignancy

Lymphoid hyperplasia of the splenic white pulp typically entails a diffuse expansion of white pulp throughout the spleen. However, rarely, lymphoid hyperplasia may manifest as one or more localized nodules. This localized form of lymphoid hyperplasia was first described in 1983, and since then, there have been no further reports in the literature. We report one additional case which was initially clinically suspected to represent metastatic malignancy. The patient was a healthy 53-year-old woman who presented with symptoms of biliary colic and underwent laparoscopic cholecystectomy. During surgery, several white-tan nodules were noted on the spleen. Diagnostic splenectomy was ultimately performed, and histologic examination and immunohistochemical characterization of the nodules revealed well-circumscribed aggregates of secondary lymphoid follicles embedded in a T cell-rich interfollicular zone, much like tertiary nodules seen in lymph nodes and unlike the normal microanatomy of the white pulp. Based on these findings, localized lymphoid hyperplasia (LLH) of the spleen was diagnosed. The aetiology of LLH is unknown, though it is speculated to represent a localized response to antigenic stimulation akin to florid reactive hyperplasia in a solitary lymph node. It is interesting that, despite the now widespread use of high-resolution abdominal imaging, LLH remains a rare diagnosis.