Primary systemic amyloidosis with a retroperitoneal mass.

A 73-year-old black woman presented with congestive heart failure, abdominal distension and ascites. A large retroperitoneal mass was demonstrated by gray-scale abdominal ultrasonography and confirmed by laparatomy and postmortem examination. This retroperitoneal mass consisted mainly of amyloid, as demonstrated by green birifringence with alkaline Congo red staining. Resistance of this staining pattern to permanganate treatment and the absence of inflammatory disease or malignancy at autopsy suggest the diagnosis of primary systemic amyloidosis. This is the first reported case of this disease manifesting as a retroperitoneal mass.