How can I remove a spam page from my website index?

@Allan-EP noindex is more appropriate. Whether or not a result is returned, the page exists. 0 is just as valid a number as any. 0 doesn’t = page doesn’t exist. 0 = 0 vendors. The danger of 404ing is that you may have a store that fluctuates between having a result for the query and not having a result. If you flip back and forth telling Google the page exists one week and not the next, it reduces confidence and could result in lost page equity/history from Google’s side. By using noindex you remove the page from the index and keep its history in Google.