Merkel Cell Carcinoma

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The subject of today’s column was suggested by a reader. To that person, I say thank you. I realize your request was several months ago but please understand that my columns are written well in advance, often two to three months before they run. I hate being under a deadline.

Skin cancers are among the most common types of cancer. Skin cancers are usually linked to sun exposure, even childhood sun exposure, as sun exposure is cumulative. The most common skin cancer is basal cell carcinoma. This cancer does not spread and is removed by skin surgery. Melanoma is much less common thankfully, however melanoma can spread, and treatment often includes surgical removal, sentinel node biopsy, and chemotherapy and/or radiation. Sentinel node biopsy is a procedure to determine whether the tumor has spread to the lymph nodes. In this procedure, dye is injected near the cancer. The dye then flows through the lymph system. The first lymph node the dye reaches is called the sentinel node. This node is removed and examined for cancer cells.

Much rarer than melanoma is Merkel cell carcinoma (MCC), also known as neuroendocrine carcinoma of the skin. Merkel cells are found at the base of the outermost skin layer (the epidermis). Merkel cells are connected to nerve endings and are responsible for the sense of touch. MCC usually appears as a flesh-colored or bluish-red nodule, often on the face, head, or neck. It is most commonly seen in older individuals with long-term sun exposure. The first sign of an MCC is usually a fast-growing, painless nodule on the skin. Although they are most commonly seen above the base of the neck, they may appear anywhere on the body, even in areas with little to no history of sun exposure. Like melanomas, MCCs grow rapidly and spread to other parts of the body. Although it is linked to sun exposure, recent research has linked MCC to a common skin virus called Merkel cell polyomavirus. How the virus causes MCC is not well understood yet. In addition, although the presence of this skin virus is very common, MCC is quite rare. This discrepancy has yet to be explained. Risk factors for MCC include exposure to sunlight and UV light (tanning beds), a weakened immune system (infections like HIV and medications used to treat cancers like leukemia), history of other skin cancers, older age (over 50), and light skin color.

Because it grows rapidly and spreads, MCC must be diagnosed and treated quickly. Once MCC is diagnosed by skin biopsy, like melanoma, the lesion is removed, usually by using the Mohs technique which ensures that the tumor is fully removed. Also, like melanoma, a sentinel node biopsy is then performed to see if it has spread. Imaging tests like CAT scans, MRIs, or PET scans are helpful to determine whether the tumor has spread. If the tumor has spread, chemotherapy and radiation therapy are employed to fight the disease. To prevent the development of these skin cancers, it is important to avoid unprotected sun exposure and never, ever, use a tanning bed.

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