Table 3.
Features to differentiate between fat-poor angiomyolipomas vs clear-cell renal cell carcinomas
| Fat-poor AML (hyperattenuating and isoattenuating) | Clear-cell RCC | |
| Tumour heterogeneity | Homogeneous | Heterogeneous |
| Calcification | Rare | Yes |
| Cystic/necrotic change | Rare | Yes |
| Enhancement pattern: early enhancement with subsequent washout | Yes | Yes |
| Enhancement pattern: gradually progressive enhancement | Possibly | Unlikely |
| Renal vein invasion | Rare | Yes |
| Signal drop on OP compared with IP | Possibly (from microscopic fat) | Possibly (from intracytoplasmic fat) |
| T2WI | Hypointense | Hyperintense |
| Co-existing classic AMLs | Common | Rare |
| Syndromic association | TS | VHL, Birt-Hogg-Dubé |
AML, angiomyolipoma; IP, in phase image; OP, opposed phase image; RCC, renal cell carcinoma; T2WI, T2 weighted MR image; TS, tuberous sclerosis; VHL, Von Hippel–Lindau syndrome.