An exceptional minute tumour incidentally found in a renal biopsy

Pathological analysis of renal biopsies performed to investigate a nephrological disease may exceptionally reveal incidental tumours, in addition to expected glomerular, tubulointerstitial or vascular pathology. We present the first case to date of a minute angiomyolipoma (AML), found incidentally in a renal biopsy specimen, performed in the assessment of proteinuria. AML is an uncommon kidney tumour, composed of a variable proportion of adipose tissue, spindle and epithelioid smooth muscle cells. Immunohistochemistry is mandatory for a definitive diagnosis, showing a specific perivascular epithelioid differentiation. The diagnosis of renal AML justifies the search for tuberous sclerosis-associated tumours.