Intraglomerular microlesions in renal angiomyolipoma

A unique case of bilateral multiple intrarenal angiomyolipomas in a 21-year-old woman with tuberous sclerosis is reported. The microscopic examination showed peculiar intraglomerular microlesions, epithelioid areas, microscopic foci of renal cell carcinoma and renal cysts, and the classical features of angiomyolipoma lesion. HMB-45 positivity was detected within some nodules and epithelioid areas. Intraglomerular microlesions were composed of adipose and smooth-muscle cells within the glomerular capillary tuft. These lesions, which were continuous with the capillary tuft, did not show any attachment to the Bowman's capsule. These findings suggest that these are not a consequence of an infiltration from the outside but were originated from inside the glomerulus. The simultaneous presence of multiple angiomyolipoma nodules either inside or outside the glomeruli, multifocality and bilaterality of these lesions, together with the HMB-45 positivity and the finding of scattered epithelioid areas supports the theory that there is a progenitor cell giving origin to all these lesions, the cell which has been named as perivascular epithelioid cell by most authors.