When a doctor takes a blood sample or a surgeon collects a tissue biopsy, it's sent to "the lab" for analysis by a pathologist. The pathologist's job is to assist in diagnosis and treatment by analyzing tissues, fluids, and cells. They are responsible for performing blood tests as well as autopsies (dissections that identify deceased patients' cause of death). A pathologist was kind enough to spend a morning showing me around "the lab."
When a surgeon removes, say, cancerous breast tissue, the tissue is sent to the pathology department. There, the tissue is immersed in a series of chemicals that render the tissue stable and that halt the reactions (including decay) that cells undergo. The tissue is mounted onto microscope slides and then stained in special dyes that colorfully render the features of cells. Sometimes, the pathologist will order special tests that test for the presence of a certain protein on the cell's surface. For example, a breast cancer drug called trastuzumab works by acting on a protein called "HER2." HER2 is expressed on the surface of tumor cells in only some types of breast cancer. By testing for the presence of HER2 on the cell surface, the pathologist establishes whether the drug can be used. In nearly all aspects of medicine, pathology findings are a valuable tool in deciding on treatment.
One of the most interesting parts of the tour was the frozen section room. A neurosurgeon operating on a patient removed some brain tissue and submitted it to the frozen section room, which is strategically placed near the operating rooms. A team prepared the sample and a pathologist put it under the microscope. Tragically, he determined that the tissue was a highly malignant form of brain cancer. Using this information, the neurosurgeon could modify his procedure to make sure that he removed all of the cancerous tissue.
Pathology is a very intellectual field that requires knowledge of rare diseases and very obscure parts of medicine. Most pathologists do not interact with patients, but they are in constant touch with doctors across all specialties. I enjoyed my inside look at this behind-the-scenes aspect of clinical medicine.
