Cruciferous veggies are a category that has been relatively well studied for its link to cancer prevention. The four petal flowers resemble a cross or "crucifer" so in case you're interested in nerdy food and health trivia, that is how this class of veggies got their name! They are filled with therapeutic vitamins and minerals that promote good health in general, and also phytochemicals or phytonutrients (substances found in certain plants which are believed to be beneficial to human health and help prevent various diseases) known for detoxification and cancer fighting properties.
Here is a list of Cruciferous veggies:
Arugula
Bok Choy
Broccoli
Broccoli Raab or Rapini
Broccoli Sprouts
Brussels Sprouts
Cabbage
Cauliflower
Collard Greens
Horseradish
Kale
Radishes
Turnips
Watercress
Wasabi
Here is a list of some ways they could prevent cancer:
Protecting cells from DNA damage
Inactivating carcinogens
Inhibiting tumor blood vessel formation
Preventing tumor cell migration
Shifting estrogen to weaker form to reduce sex hormone related cancers
Protecting against viruses and bacteria
Preventing inflammation
Research is still being analyzed, and there is evidence that an individual's gene-diet interaction impacts how long the body retains and utilizes protective cruciferous nutrients in the body. This accounts for variation in research results. Since there are few down sides to consuming plenty of well prepared, lightly cooked cruciferous veggies for most individuals, I suggest increasing their daily presence in your diet!
NOTE: Copious amounts of raw cruciferous veggies may affect thyroid function, please consult your doctor if you have a thyroid condition.
Recipe Ideas:

Roasting: Brussels sprouts, Cauliflower or Broccoli with olive or coconut oil, garlic, sea salt and your favorite herbs or spices....try turmeric and black pepper to kick cancer and inflammation fighting up another notch!
Sautéing: greens lightly, like kale (Lacinato or dinosaur is my personal favorite) or collards using this flavor profile: salty, sweet, bitter, heat. An example is to use coconut oil for sweet, sea salt, your favorite vinegar for acid, Siracha or crushed red pepper flake for heat.
Bon Appetit and Salud!
http://www.aicr.org/foods-that-fight-cancer/broccoli-cruciferous.html
http://www.stopcoloncancernow.com/spread-awareness/news/cruciferous-vegetables-prevent-cancer
