The processing of tissue from a mesothelioma biopsy

How a Tissue Sample is Processed

Although the surgeon conducting a biopsy procedure may have some opinion as to a possible mesothelioma diagnosis based on the visual appearance of the tumor and the surrounding area, it is necessary for a pathologist to process the sample before a definitive diagnosis can be made.

Once the specimen is removed, it is labeled with the patient's name along with any other information necessary to identify it. It is then examined by a pathologist who makes note of how it appears to the naked eye, including its color, weight and size. This is referred to as a "gross" description. These visual findings are then dictated and become part of the patient's medical record.

The next step is for the tissue to be reviewed under the microscope to determine how it compares with normal cells, however, before this can be done, it must be prepared in one of two ways. In a "frozen" section, the doctor removes the tissue and it is immediately frozen, then cut into thin layers, mounted on a slide and stained with dyes that will show parts of the cells such as the cytoplasm and nucleus. This method has the advantage of yielding quick results, and is useful if further surgery may be done in conjunction with the biopsy.

In a "permanent" section, the tissue is placed in formalin for several hours, ensuring that proteins in the cells become preserved, and will not change. A special machine is then used to remove water from the tissue, and the tissue is then embedded in a paraffin block. When the block has hardened, thin slices of the tissue are cut and are carefully placed on a slide. Once on the slide, the paraffin is dissolved and the water is restored. The specimen is then stained with dyes. This process usually takes several days. In additional to routine stains such as hematoxylin and eosin, more in depth immunochemical stains may be used to help distinguish one type of cancer from another.

When one or more slides have been made, the pathologist evaluates them under the microscope, and describes the type of cell and how they are arranged as well as noting any other characteristics or irregularities seen in the sample. These findings are then dictated and included in the pathology report. The final diagnosis is the end result of the process that includes biopsy, gross examination, processing and microscopic evaluation. Pathology reports may contain technical and medical terminology meaningful mostly to other medical professionals. Patients should feel free to review their reports with their doctor, and should request a copy for their own records.

Although most cancers can be easily diagnosed, mesothelioma is a rare cancer that can sometimes present a challenge. If the pathology report is in any way inconclusive, a second opinion may be necessary. There are expert pathologists available at some of the National Cancer Institute-designated cancer centers, and the Armed Forces Institute of Pathology (AFIP) can also provide a second opinion. The facility should be contacted in advance to confirm availability of service, cost and shipping instructions. Slides and/or the paraffin block from the original pathologist who examined the sample, or from the hospital where the biopsy procedure was conducted need to be obtained. Patients interested in a second opinion should discuss the possibility with their doctors.

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