Castleman's Disease Presenting as an Unusual Pelvic Retroperitoneal Mass.

Castleman's disease (CD) is characterised by benign lymphoepithelial proliferation and is a peculiar form of angiofollicular lymph node hyperplasia rather than a neoplasm or a hamartoma. CD is broadly classified as unicentric CD (UCD) and multicentric CD. In the unicentric variant, patients have localised disease affecting only a single lymph node or a group of adjacent nodes in a single region, which clinically presents as an enlarging mass without any other significant symptoms.