The present invention is directed to an assembleable unit of cassettes for containing specimens for histological examination. The cassettes are each designed for stacking relation one to another by snap locking means which are preferably configured to provide an audible sound and “click” feeling when stacked. A cover is provided to complete a stack, thereby providing an integral unit for case management. The unit is so integrated that it can be handled and will not disengage the stacked cassettes in the usual handling process in the laboratory. It is also readily processed in a paraffin bath for preparing the contained specimens for microtomy. Thus, a stabilized unit is provided for multiple specimens from a single source and maintaining them in sequential order without individual handling.