• Jena Martin MD

Thinking Inside The Box

In computer science this is called Black-Box Testing and it closely mirrors most clinicians understanding of pathology. 

Hospital pathology work starts with a question – what is it?  These questions, understood as ‘tests’ in medical parlance, are put to the pathologist in the form of a specimen.   You might be most familiar with the laboratory from blood tests, and these specimens are also analyzed by pathologists.  But my work focuses on the hard parts of you, the 'something' you have had removed by a doctor in a clinic or operating room.

We call those ‘somethings’ tissue.  Everything removed from the body, from hip joints to breast specimens, is examined in the pathology laboratory.   After these things are removed, they are sent, either walked fresh from the operating room (O.R.) or placed in a formalin-filled jar, to the most important room in the hospital - the laboratory, also called the pathology department.   

Let's imagine you've had a skin biopsy *.   Taken from your Mid Upper Back, and deposited into a formalin containing jar, it was brought to the laboratory.

We describe the biopsy, measuring its length width and depth, and note any discoloration.   

We often apply ink to the bottom surface, so that we can easily track your biopsy as different from others.  For larger specimens, the ink helps us under the microscope to more easily determine the tissue edges (the margins).

We cut your biopsy twice, so that it is in three pieces (trisected).

These small chunks of your biopsy are placed into little plastic boxes we call cassettes (this one has a blue sponge inserted to keep the tissue smooth). 

Then this cassette containing your biopsy is put into a machine called a processor, where it is bathed in a sequence of dangerous and toxic chemicals.  The chemicals kill organisms, cross-link the DNA inside your cells, and preserve the structure of your skin biopsy.  

After your tissue is finished processing, around 4 am the following morning, histotechnologists remove the cassettes from the processor machine and set your tissue into wax - making it hard enough to cut.

We call this wax square containing your tissue  ''The Block". 

The histotechnologist cuts this block (your biopsy in wax) into tissue paper-thin slices , floats each in a dish of water, and lays each piece carefully onto a glass slide.

Note that these thin slices of tissue have no color - without blood we are translucent.  To help us see the biopsy, these slides are then stained with a combination of pink and purple dyes and covered with a thin glass top (the coverslip).  This all happens inside an automated machine.

The slides are sorted and matched to the paperwork your doctor sent to the lab and all of this is delivered to a pathologist by 8 am.

And that's when I get to work.

* If you have questions about your skin biopsy, I'd recommend this overview from Mayo Clinic.  https://www.mayoclinic.org/tests-procedures/skin-biopsy