Benign mesenchymal tumours and tumour-like lesions in end-stage renal disease.

AIMS: Mesenchymal neoplasms of the kidney are rare, and most represent sporadic angiomyolipomas. A few haemangiomas have been reported in end-stage renal disease (ESRD) but, to date, no study has focused on the frequency and morphological spectrum of mesenchymal lesions in ESRD. METHODS AND RESULTS: We evaluated retrospectively 90 nephrectomy specimens with ESRD. Haemangiomas were detected in eight cases (8.8%; six males and two females; mean age: 55 years); four were multifocal and four had concurrent renal epithelial neoplasms. Lesions involved the medulla (three), cortex (two) or both (three), and the size range was 1-25 mm (mean 4.8 mm). Histologically, all were capillary haemangiomas with an at least focally detectable spleen-like anastomosing pattern. All tumours stained positively for CD31 and FLI-1, but none expressed pankeratin (KL-1), podoplanin/D2-40, HHV8 or GLUT-1. Minute angiomyolipomas (mean size 2.3 mm) were detected in four patients (mean age 49.5 years). Tumour-like smooth muscle proliferations were seen surrounding muscular arteries (eight), occasionally admixed with fat extending from the renal sinus mimicking angiomyolipoma. No similar tumours were found in 105 control kidneys. CONCLUSIONS: Benign haemangiomas are not uncommon in ESRD, but may be under-recognized. They display distinctive morphology and should be distinguished from angiosarcomas and capillary-rich renal cell carcinomas.

Incidental monotypic (fat-poor) renal angiomyolipoma diagnosed by core needle biopsy.

We present the case of a 55-year-old patient with a history of chemotherapy and bone marrow transplantation because of acute myeloid leukaemia. An incidental 4 × 3 cm measuring renal mass was detected while performing a magnetic resonance imaging (MRI) for lumbago. The lesion was suspected to be either a renal cell carcinoma (RCC) or a leukemic infiltration. To decide about further treatment a percutaneous core needle biopsy was performed. Histology showed a monotypic angiomyolipoma, a relatively rare benign renal lesion. Interestingly, in cross-sectional imaging, angiomyolipoma was not taken into differential diagnostic account because of lack of a fatty component. Due to bleeding after biopsy the feeding artery of the tumor was occluded by microcoils. This case demonstrates the utility of biopsy of renal tumors, in particular when small tumor-like lesions are incidentally detected to decide about the right treatment and thereby avoiding nephrectomy.