PMC3324151_01
(a-d) Axial MR images of the left kidney, T1-weighted in-phase (a) T1-weighted opposed phase (b) T2-weighted fat-saturated (c), and T1-weighted, contrast-enhanced fat-saturated (d). The left renal mass is isointense in T1-weighted imaging without evidence of fatty components (a, b); the small hypointense spots in fat-saturated T2-weighted imaging are vessels (c). The mass is hypointense in T1-weighted imaging after i.v. contrast media (d); solley centrally there are KM-enhancing foci representing vessels (d).
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fig1
As fatty tissue could not be identified, an angiomyolipoma was not included in the differential diagnosis (Figures 1(a)-1(d)).
Representative findings of the kidney biopsy (a) with the angiomyolipoma (b-e). (a) Light microscopy of the kidney, hematoxylin stain (magnification x4). (b) Light microscopy of the angiomyolipoma, hematoxylin stain (magnification x100). (c) Higher magnification of the tumor showed large spindled and epithelioid cells with clear and eosinophilic cytoplasm intimately associated with slit-like vascular channels, (magnification x400). (d) Immunohistochemistry using an antibody against actin (magnification x100) shows a strong positivity of the smooth muscle component of the tumor. (e) Immunohistochemistry using an antibody against HMB-45 (magnification x100) shows a few positive tumor cells.
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fig2
On histology renal parenchyma from the cortex showed 8 glomeruli with a slight increase of mesangial cells and matrix and ectatic tubuli (Figure 2(a)). Infiltration of acute myeloid leukaemia could be excluded histologically (Figures 2(b)-2(c)). The tumor cells were strongly positive for smooth muscle actin (Figure 2(d)). Scattered large tumor cells showed a strong granular cytoplasmic positivity for HMB-45 (Figure 2(e)).