Giant bilateral perinephric tumour and overt proteinuria

Abstract

Keywords: angiomyolipoma; computed tomography;focal segmental glomerulosclerosis; kidney cancer;liposarcoma; proteinuriaA 63-year-old man with type 2 diabetes mellitus andhypertension presented with increasing abdominalgirth and foamy urine for the previous 2 years.Impaired renal function (BUN 33mg/dl, serum crea-tinine 2.3mg/dl), hypoalbuminaemia (2.3g/dl), overtproteinuria (11.2g/day), microscopic haematuria(RBC 21-35/HPF) and bilateral perinephric tumourwere noted at a local hospital. Non-contrast enhancedcomputed tomography of the abdomen confirmedgiant bilateral perinephric tumour with fat component(Figure 1). The differential diagnosis included retro-peritoneal liposarcomas or bilateral angiomyolipomaarising from renal capsule. After referral, physicalexamination revealed distended abdomen withoutpalpable mass. Magnetic resonance imaging(T1-weighted) demonstrated a lipomatous tumour ofabout 10cm in size, in the bilateral perinephric space(Figure 2). There was absence of radiological featuresof angiomyolipoma, including linear or branchingappearance of intra-tumoural vessels with evidentcontrast enhancement, aneurysmal dilatation of intra-tumoural vessels, haemorrhage within and outside thetumour, and the bridging vessel or beak signs [1].Hence, bilateral perinephric liposarcoma was favoured.However, a sonography-guided needle biopsy of theleft tumour showed only fibroadipose tissue, withoutidentification of malignant cells. The simultaneousneedle biopsy of left kidney revealed focal segmentalglomerulosclerosis (FSGS). Considering the invasiveclinical course of the tumours, bilateral radicalnephrectomy, with excision of the retroperitonealtumours, was performed. The pathology disclosedwell-differentiated liposarcomas with encasement ofbilateral kidney and involvement of the renal sinus,and further confirmed FSGS. The patient thereafterunderwent regular uneventful haemodialysis. TheFSGS and liposarcomas may just be coincidental inthis patient. However, the probability of bilateralperinephric liposarcoma with secondary FSGS stillcannot be completely excluded.Around 12–40% of liposarcomas occur in theretroperitoneum [2,3], and of these, 35% originate inthe perirenal fat [2]. Although liposarcoma is the mostcommon retroperitoneal soft tissues sarcoma, retro-peritoneal liposarcoma comprises only about 0.1% ofall cancers [2,3]. Liposarcomas tend to grow slowly in