Broccoli, Cauliflower, Kale, Cabbage, and Brussels sprouts all evolved from the same plant species: The Wild Mustard Plant. Farmers in different areas just chose to selectively breed different portions of the same plant. Broccoli was bred from choosing large buds and large stems. Cauliflower was just the flower bud. Brussels sprouts, Cabbage, and kale were all leaves from different portions of the plant.
So albino broccoli is really a pretty close description.