156 A Unique Case of Castleman Disease Involving a Retroperitoneal Accessory Spleen

Abstract Introduction Castleman disease is a lymphoproliferative process first described by Dr Benjamin Castleman in 1956. It has been reported to occur in various sites; however, accessory splenic involvement has only been reported once before. Clinically, it is divided into a solitary and a multicentric form. About 90% of the solitary forms are of the hyaline-vascular type, which shows enlarged follicles with tight concentric layering of lymphocytes, vascular proliferation within the follicles with central perivascular hyalinization. The interfollicular parenchymal usually shows prominent vascular proliferation admixed with a mixed inflammatory cell population. Our aim is to report a unique case of unicentric hyaline-vascular type Castleman disease involving a retroperitoneal accessory spleen that presented in an otherwise healthy woman. Method This is a retrospective review of a case of a 32-year-old woman who presented with a retroperitoneal mass incidentally discovered on an abdominal ultrasound. Results Radiographic studies showed a 6 cm contrast enhancing mass posterior to the pancreas clinically suspicious for malignancy. Fine needle aspirations failed to provide diagnostic material and the mass was surgically excised. The specimen showed a mixture of red and white pulp typical of splenic tissue. Enlarged follicles with concentric tight layering of small lymphocytes surrounding hyalinized central small blood vessels were present, as well as increased red pulp vascularity. Flow cytometry showed no evidence of a monoclonal lymphoid population. The findings were diagnostic of hyaline vascular type Castleman disease occurring in accessory splenic tissue. Conclusion Unicentric Castleman disease usually acts in a benign fashion but can present in a variety of unusual sites including accessory splenic tissue and can be clinically confused with malignancy. Excisional biopsy is the procedure of choice for accurate diagnosis.