Gross dissection covers a wide variety of tasks that are performed in medical labs which ranges from removal of surgical samples from a patient to slicing up a needle core biopsy. When I was working for an oncology lab, the dissection I routinely performed was on small surgical samples that arrived in formalin.
The lab I worked in received samples from all over the world. Sometimes they came from a hospital that had a tissue processor and an embedding station. These tissue samples were already in a paraffin cassette and required nothing further in preparation of microtomy. Some of the odder samples we received were processed tissue in a square block of paraffin, large pre-cut tissue (for larger plastic cassettes), and whole organs or huge amounts of fatty tissue in large formalin vials.
Gross dissection is really the first thing that needs to occur to a tissue sample before we can process it through the lab. Without the tissue going through a tissue processor, which removes most of the water out of the sample, we can not cut it up or run any tests on it. So, I volunteered to be the person that came in on the weekends to gross the surgical samples we received.
The first step is looking at the pathology report to determine what part of the body the tissue came from. This information may help us determine how to section the tissue if it is too large to fit in one of our paraffin molds. The next step is measuring the dimensions of the tissue and determining where the tumor is. The major idea behind gross dissection for our purposes, is to expose the largest area possible so we have a lot of tissue to look over during the immunohistochemical (IHC) tests. The last step is determining if it needs to be bisected, trisected, loafed, or many other forms of further cutting.
During the measuring and cutting process, we had to take extremely detailed notes on what color the tissue was, it’s dimensions, all the personal identifying writing on the formalin vial, and how it was cut and placed in x number of plastic cassettes. Once those notes were good, we would place all of our tissue cassettes into a tissue processor, dry out the tissue, and then embed it in paraffin using the right sized mold for the tissue. Most modern day labs all use formalin fixed paraffin embedded (FFPE) blocks for microtomy. It’s really the industry standard, and it is what I have the most experience with.
