For larger tissue specimens without complicated margins or stratified layers, the orientation is simply to find the cut surface. Most of these types of specimens will be embedded flat on this cut surface so that the cut surface is placed flat against the block face (bottom, most recessed surface of the mold). Your main concerns will be with getting the specimen as flat as possible and leaving a border of paraffin surrounding the outside edge of the tissue. For any tissue which is dense or rigid in the block face, it is helpful to place at a slight angle within the embedding mold. This will aid with microtomy. Examples of tissue types that might be easiest to cut at a slight angle are uterus body, thyroid, and prostate gland wedges. Large fatty pieces, such as large sections of breast tissue or lipomas, may not have a distinct cut edge, but should be embedded to show the greatest surface area. It is important to also be sure to leave a heavy border of paraffin to help contain the fatty tissue and hold the section together on the water bath during microtomy.
