Merkel Cell Cancer: Rare, but Deadly

On the opposite end of the skin cancer spectrum from basal-cell carcinoma is Merkel cell cancer. While basal-cell is the most common type of skin cancer, Merkel cell is extremely rare. Basal-cell tumors grow slowly and hardly ever metastasize, while Merkel cell is more aggressive than melanoma and has a higher mortality rate.

“Merkel cell was always the orphan disease,” says Christopher Bichakjian, M.D. (Residency 2001), an assistant professor of dermatology and founder of the U-M Cancer Center’s Multidisciplinary Merkel Cell Carcinoma Program. The U-M Health System is one of just three medical centers in the country with a treatment and research program devoted to Merkel cell cancer. “It’s so rare that no one sees enough patients to develop expertise in how to treat it. Many physicians see just one or two patients with Merkel cell cancer in their entire careers.”

Because the disease is so rare and no one specialty treats patients with this type of skin cancer, treatment is inconsistent. Head and neck surgeons have one protocol; surgical oncologists have another. It is often misdiagnosed as basal-cell cancer and long delays before diagnosis are common as patients are passed from physician to physician.

“Another difficulty with Merkel cell cancer is that it doesn’t look like anything in particular,” says Bichakjian. “It has no characteristic features, so the patient thinks it’s just a little red bump and it’s not growing or hurting. When they eventually see a physician, the doctor says it looks like a little cyst or basal-cell cancer. Eventually, it gets biopsied, but there’s often a delay. That’s a problem, because Merkel cell carcinoma is an aggressive disease that spreads from skin to lymph nodes. If you can catch it in a lymph node before it goes anywhere else, you have a chance of containing it.”

Merkel cells in skin are connected to peripheral nerves that transmit touch, temperature and pain signals to the brain. Researchers don’t understand exactly how Merkel cells work or what causes them to become malignant, but they know the cancer is most common in elderly people or those without a healthy immune system. One intriguing clue was the discovery in 2008 that genes from many Merkel cell carcinomas contained DNA from a type of virus known to cause tumors in mice. This led some researchers to speculate that Merkel cell cancers could be caused by infection with the virus.

“You find the virus in about 80 percent of Merkel cell tumors,” says Bichakjian. “But whether the cancer is caused by the virus is not yet proven. We know that 60 percent to 70 percent of the population has been exposed to this virus and the vast majority of these people are not going to get Merkel cell cancer. Plus, 20 percent of tumors don’t have the virus at all.”

Early in 2006, Bichakjian established the Merkel Cell Program, which is modeled after the Health System’s 20-year-old Multidisciplinary Melanoma Program. In the last four years, the program has treated 160 patients from Michigan and surrounding Midwest states and Bichakjian gets weekly calls from patients or family members in other areas.

“When we started the program, one of our first goals was to develop a treatment algorithm based on our experience and the literature that’s out there,” says Bichakjian. “We don’t have a miracle drug for Merkel cells. Our scalpels are no different from other surgeons’. But what we can offer is a multidisciplinary, consistent approach to treatment with detailed data on how our patients respond. After four years, we feel comfortable that we own Merkel cell and its management.” —SP

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