Have a questionable 4mm angiomyolipoma in upper pole of right kidney. radiologist seemed unsure. what else could it be that resembles angiomyolipoma?

Small lesion: 4 mm is very small lesion and differentiation from cyst or other tumor difficult. Angiomyolipomas are benign and composed of variable amounts of three components; blood vessels (-angio), plump spindle cells (-myo) and adipose tissue (-lipo).If fat content recognized on ct or mr tumors likely to be angiomyoliipomas. Other tumors can have some fat content.

Too small right now: This is too small to worry about. Unless it becomes bigger with more time, you can ignore it. I would ask you to get it rechecked it in 6 to 12 months and look for any growth if it gets larger than it has to be removed which is the best way to manage it provided it is getting bigger in size.