The Fascinating World of the Pathologist

A pathologist is a physician who examines tissues and fluids from the body and renders a diagnosis based on his/her findings. Pathologists participate in a 5 year residency program and then are eligible to sit for the examination given by the American Board of Pathology for certification.

First the pathologist processes the specimen in either or both of the following ways: a permanent section and/or a smear. A permanent section places the fresh specimen in a fixative (fluid) for several hours, depending on the size of the specimen. Formalin is the general fixative of choice - a combination of formaldehyde gas and buffered water. This process makes the cells harden and become "fixed". This fixed specimen is then placed in a machine which removes all the water from the specimen and replaces it with paraffin wax. This occurs overnight. The next day the histologic technician embeds the specimen in a large bloc of molten paraffin. It is solidified by chilling and then is cut into thin slices by a microtome. These sections then float out of a water bath and are placed onto glass slides.

The paraffin is dissolved and with the help of solvents, water is added back in. The slides are then stained. The dyes used commonly include hematoxylin (H) and eosin (E). These yield colors of pink, orange and blue and make it easier to identify different cells. The nucleus of a cell is usually stained blue, with the cytoplasm is pink or orange.

Another type of specimen is the frozen section. This section can be looked at within a few minutes of removal. These sections are not as good as permanent sections and are not as durable. Their immediate assessment though can be of great importance to the patient and surgeon in certain circumstances.

The other type of specimen is the smear. This is a liquid or small particles in liquid. The sample is "smeared" on a slide and air-dryed or set with a fixative spray. The smears are then stained, covered and examined under a microscope. Smears can be examined almost immediately.

The pathologist does two types of examinations: the gross description and the microscopic examination. "Gross" really means how it appears to the naked eye. This dictated description usually includes the exact way it was labeled, a description of what it looks like and includes measurements. The slide or cassette is identified (Cassette A) and how it was cut, if at all, is noted. Sometimes the gross description includes weight, a description of the texture of the surface and the coloration. Certain diagnoses can be ruled out at this point. All slides are identified as to which section of the specimen is included.

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