Currently, the 2D image mapper performs the annotation for 2D images which have a volume property (e.g. a segmentation with the volume of "20 ml").
To achieve a clear software architecture, this should be done by an other class. This could be called mitkVolumeAnnotationVtkMapper2D or simply mitkVolumeAnnotationMapper. There are mappers in VTK especially for text rendering. I will specify this more soon.