In RoboHelp 7 breadcrumbs are all or nothing. Either off or on. In version 8 what you can do to have them appear only in selected topics is to define a Master Page. In the Master Page you may insert a Breadcrumb placeholder (or not) as desired. Then apply the Master Page to specific topics to influence the outcome. In this case you would want to turn off Breadcrumbs in the layout properties (I think) as that would govern whether you get the all or nothing. Then because the placeholder is in the topic via the Master Page, you get them only in the topics you want.
Thank you, Rick! It's much work, but the result is great and it works perfect!
Apart from MasterPage RH8 allows you to insert breadcrumbs placeholder directly in the topics also. This way you can have finer control over which all topics you want this in and you can control the location within the body of the topic.