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Skin Cancer and the Frozen Section Histology Procedure
Common Skin Cancers
Skin cancer is reportedly on the rise in the United States. The two types of skin cancer which are most predominant are basal cell carcinoma and squamous cell carcinoma. Basal cell accounts for 90% of all skin cancer. These two types of skin cancer, while serious, are very treatable when discovered and treated early. A third type of skin cancer, and by far the most deadly, is melanoma. Basal cell carcinomas can appear anywhere on the body, but typically they show up in one or more of the following places:
Cryostat, used for frozen sections
The Frozen Section Histology Procedure
I have worked in a histology laboratory for twelve years as a histology technician. This is the department which performs a procedure called the frozen section or cryosection. When a person comes to the hospital to have a lesion removed, the surgeon quite often will send the specimen to the laboratory for immediate analysis during the surgical procedure. Here is a step by step description of the frozen section procedure that occurs as the surgeon, surgical staff and patient wait in the procedure room.
- The specimen is delivered to the histopathology department.
- The specimen is properly identified and the patient information is entered into the patient’s computer file.
- The specimen is given to a pathologist or pathology assistant.
- The tumor is located in the specimen.
- Piece(s) of the specimen suspected of containing tumor are cut to be used for obtaining frozen sections.
- The histology technician places the tissue onto a small metal disc with a viscous medium.
- The tissue and metal disc are placed in a cryostat to freeze at -20 to -30 degrees Celsius (-4 to -22F).
- The frozen tissue is placed on a cutting instrument in the cryostat called a microtome.
- A five micrometer thin cross section or frozen section of tissue is cut and placed onto a glass slide.
- The slide is dipped into various reagents including eosin dye which stains the cell cytoplasm pink and hematoxylin which stains the nucleus deep blue.
- A cover slip is placed on the slide, over the tissue.
- The pathologist looks at the tissue under a microscope to determine malignancy and to see if the margins of the tissue are clear of cancer cells.
- The p[athologist reports findings to the surgeon in the operating room via phone and intercom.
- If margins are not clear, the frozen section procedure is repeated on new tissue provided by the surgeon.
Cutting a frozen section of tissue in the cryostat
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The Mohs Procedure
A more intense and extremely effective basal cell skin cancer treatment is called the Mohs Procedure, named after surgeon Frederic E. Mohs in the 1930s. In this procedure, every piece of skin removed from the patient is cut as a frozen section (see above) and examined microscopically. If any cancer is seen extending to the margins, the surgeon goes back and removes more skin. This procedure is the best at removing as little healthy skin as possible while removing all of the cancerous tissue. the Mohs procedure cure rate is between 97% and 98.7%. This is different from the technique used in the routine frozen section procedure. Using that technique, only skin in which tumor can be seen with the naked eye is examined microscopically.
Frozen section procedures, especially the Mohs procedure are the most effective treatment for basal cell and squamous cell skin cancers at the present time. Because of these techniques, basal cell and squamous cell skin cancers can, in the vast majority of cases, be cured.