Fascism is basically a dictatorship that does whatever it can to remain in power.
Communism is just the grouping of blah blah and blah. Without limitations a single person(the person in charge of the thing overall) can easily take over it all and turn it into a "Fascist State".

Actually, if something was set up along the lines of a Representative Democracy based around a Communist economy/society you'd see it working quite nicely, so long as said limitations/checks and balances were in place.