Mohs micrographic surgery is the most effective way of removing certain skin cancers, particularly those that spread deep and wide with little finger-like or root-like projections. This kind of tumor spread is called contiguous or direct spread and differs from metastatic spread by invading only local tissues and not distant sites such as lungs and liver. Contiguous spread pushes normal tissue out of the way or simply destroys it. Tumors that spread this way include skin cancers such as basal cell and squamous cell carcinoma. There are also a large variety of related skin tumors called appendageal tumors which can spread contiguously. These types of tumors are all capable of being treated by Mohs Micrographic Surgery.
Mohs Micrographic Surgery, or simply Mohs Surgery, is named for Frederick Mohs, the surgeon who developed the technique. Mohs Surgery differs from conventional surgery in the way the tumor is removed and in the examination of the removed tissue sspecimen. In skin cancer treatment, the skin tumor is initially debulked. After debulking, the area involved with visible tumor is removed surgically in a thin beveled disc. A diagram of the involved area is constructed, and the skin and the specimen are scored to help maintain proper orientation and positioning.
Once removed, the disc-shaped specimen is cut into smaller pie-shaped pieces. Each piece is numbered and color-coded with several dyes so that the surgeon can identify the original position of each piece and the correct orientation on the skin. All of this information is transferred to the diagram which was originally created. The tissue is taken for immediate processing. While the tissue is being processed, a dressing is placed on the patient's wound. Processing can take about thirty minutes for an average amount of tissue but may take longer for larger amounts of tissue.
Tissue processing is an important step in helping to identify any areas of residual tumor. During the processing, the tissue is compressed and frozen rapidly with liquid nitrogen. The tumor is then cut into extremely thin sheets from the bottom surface up, with a machine called a cryostat. These thin sheets of tissue are then put on a microscope slide and stained. Once the staining is completed,the tissue is ready for microscopic examination.
If tumor is present, the location and orientation may be deterimined because of the color-coding which was completed immediately after the tissue was surgically removed. The information is transferred to the diagram which will then serve as a map. The map helps locate the position any residual tumor that must be subsequently removed.
If a second stage of Mohs Surgery is necessary, only those areas where for residual tumor is identified will be removed. This preserves as much normal tissue as possible. All other surgical steps, including color-coding, processing and microscopic evaluation are repeated. Stages are repeated as many times as necessary to completely remove the skin cancer.
Once the Mohs portion of the surgery is completed, a defect or hole will remain where the skin cancer was removed. The complexity of the repair will depend on the size and location of the defect. The most complex repairs involve reconstruction of defects involving the face. At Harmonie Medical, facial reconstructions are completed by board certified facial plastic surgeon, Dr. Achih H. Chen.
Not all skin cancers require Mohs surgery. The procedure is usually selected for tumors growing in high-risk areas of the face such as the nose, eyes, mouth, ears and surrounding tissue. It is also selected for all recurrent tumors (those reappearing after having been removed), all large tumors and all tumors which look aggressive under the microscope.
Dr. Daniel Sheehan, Mohs Surgeon and Board Certified Dermatopathologist
Dr. Daniel J. Sheehan, Director of Harmonie Medical and formerly Director of Mohs Micrographic Surgery and Director of Dermatopathology at the Medical College of Georgia is a very experienced Mohs Surgeon who is not only board certified in Dermatology, but is also board certified in Dermatopathology. Dermatopathology is the medical specialty of microscopically examining skin specimens. This is the most critical portion of Mohs surgery as microscopically examining tissue specimens is vitally important in determining the complete removal of skin cancer. Dr. Sheehan's additional level of expertise in Dermatopathology helps give patients the skill they want and need in state-of-the-art skin cancer care.
More Information on MOHS Surgery from American Society for MOHS Surgery