It may not be possible to excise some MCCs on the face with a margin margin The edge or perimeter of the tissue removed in cancer surgery. The margin is described as "clear" or "negative" when the pathologist sees no sign of cancer cells under the microscope, suggesting that all of the cancer has been removed. The margin is described as "positive" or "involved" when the pathologist finds cancer cells in the edge of the tissue. This suggests that not all of the cancer has been removed. Certain cancers such as Merkel cell carcinoma can have negative microscopic margins despite residual cancer cells being left behind because MCC often "skips" via local lymphatics to adjacent areas and does not grow a single continuous mass. of more than 1 cm. For these reasons, a doctor may refer a patient to Mohs micrographic surgery. Mohs micrographic surgery allows for conservation of skin to maintain function and appearance of sensitive areas of the body (such as the face). Local Local Affecting only the site of origin, without evidence of spreading. Compare to systemic. removal of the MCC is evaluated under the microscope during surgery. Our analysis of published studies on the treatment of MCC suggests that radiation therapy radiation therapy The use of radiation to kill cancer cells and shrink tumors. Merkel cell carcinoma is a highly radiation sensitive cancer in most cases. needs to be added to Mohs micrographic surgery to optimize control of the disease, as MCC often “jumps” several centimeters to nearby skin. Addition of radiation therapy to Mohs micrographic surgery appears to cut recurrence by roughly one-half (see table below, adapted from Longo & Nghiem, 2003). A challenge of using Mohs micrographic surgery for MCC is that a sentinel lymph node biopsy sentinel lymph node biopsy Removal and examination of the "sentinel" lymph node(s). Sentinel nodes are the first lymph nodes to which cancer cells spread from a primary lesion. To identify the sentinel lymph node(s), a radioactive substance and/or dye is injected near the primary lesion. The surgeon uses a Geiger counter to find the lymph node(s) containing the radioactive substance or looks for the lymph node(s) stained by the dye. The surgeon then removes the sentinel lymph node(s) and sends them to a pathologist to check for the presence of cancer. almost always needs to be done at a separate appointment (prior to having the cancer cancer A term used to describe diseases in which abnormal cells continually divide without normal regulation. Cancerous cells may invade surrounding tissues and may spread to other regions of the body via blood and the lymphatic system. fully removed by Mohs surgery Mohs surgery Also called "Mohs micrographic surgery". A surgical procedure used to treat some skin cancers. Circumferential (like an onion) tissue layers are removed and examined under a microscope one at a time until all cancerous tissues appear to have been removed. While it is occasionally an appropriate therapy for Merkel cell carcinoma, Mohs surgery is an optimal therapy for tumors such as basal cell carcinoma on locations for which minimizing surgical margins is important (face, etc.). Mohs surgery usually cannot be performed at the same time as a sentinel lymph node biopsy, which may be very important for MCC management. ), so this makes scheduling inconvenient.
In most skin cancer types, Mohs micrographic surgery yields local “cure” rates that are close to 100%. The risk of recurrence after Mohs surgery for MCC is far higher (probably around 20% if no radiation is given), in part because MCC is much more likely than other skin cancer types to “jump” by several centimeters in the skin, even after a microscopic examination of the tumor margins is negative.
Mohs micrographic surgery might make sense for MCC patients that have local disease presenting on the face, who have already had a sentinel lymph node lymph node A rounded mass of lymphatic tissue that is usually surrounded by connective tissue and about the size of a green pea. Lymph nodes filter lymphatic fluid, also know as lymph, which is fluid that drains from the tissues of the body and contains immune cells. Cancer cells often travel through lymph vessels and lodge and grow in lymph nodes, sometimes causing the nodes to markedly increase in size. biopsy biopsy The removal of cells or tissue in order to determine the presence, characteristics, or extent of a disease by a pathologist usually using microscopic analysis. .
Patients that have disease beyond their primary tumor (lymph nodes, metastatic metastatic Having to do with the spread of cancer from a primary site of origin to distant areas beyond the draining lymph nodes. sites) and those that are at high risk of recurrence may want to have a wide local excision excision The removal of tissue of interest by surgery. instead of Mohs surgery. Because radiation often needs to be given anyway to lower recurrence rates, some of the benefits of Mohs surgery that are important in other cancer types like basal cell carcinoma basal cell carcinoma Skin cancer that arises from basal cells, a cell type found in the innermost layer of the epidermis. Compared to other skin cancers, basal cell carcinoma is rarely lethal. Less than 1 in 50,000 patients with basal cell carcinoma will die from this disease. are lost when treating MCC with this special surgical technique.
Minimal side effects from the surgery, but may have slightly higher chance of recurrence, as compared to a wide excision, unless radiation is given after surgery.
Typically not. Mohs surgery is typically done in a dermatologist’s office. A sentinel lymph node biopsy is typically done in an operating room by a surgical oncologist, using general anesthesia. If a patient needs a node biopsy, it typically needs to be done in advance of Mohs surgery, by a different physician.
The authoritative source on Merkel cell carcinoma.
September 13, 2019