The Rise of a ‘Rare But Increasingly Common’ Skin Cancer

Merkel cell carcinoma (MCC) is a rare form of skin cancer that is currently on the rise in the U.S. According to the Skin Cancer Foundation, an estimated 3,000 new cases of MCC are diagnosed per year in the U.S., and it is expected to increase to 3,250 cases per year by 2025.

Although not as common as other forms of skin cancer, it is still important to know the risk factors and signs of MCC. CURE® spoke with Dr. Brent Moody, of the Skin Cancer Surgery Center in Nashville, Tennessee, to learn more about major takeaways from his presentation at the recent CURE® Educated Patient® Skin Cancer Summit and why it’s so important to visit experts of the cancer, the need for more robust data in this area and how a common virus may play a role in this disease.

CURE®: Why is it so important to discuss MCC and why don’t we hear about it as often as other skin cancer types?

Moody: (MCC) is becoming a more important skin cancer. There's really no question that the incidence of (MCC) is rising. We don't fully know why that is, but it's something that we're observing. Also, (MCC) really requires a multidisciplinary team approach for optimal management. I think it's really important that more people know about (MCC) so they can understand how it is different than the other skin cancers and how we like to approach it.

We don't hear as much about (MCC) as we do about the more common skin cancers such as basal cell carcinoma, squamous cell carcinoma and melanoma simply because (MCC) is much less common than the other skin cancers.

What is the incidence rate of MCC?

One of the challenges we face with (MCC) is a lack of great data, so the statistics are not as precise as we have for other skin cancers. I've seen some estimates that there may be only a few thousand (cases) of these every year in the United States. But again, we don't have as great a handle on statistics with (MCC) as we do (with) some of the other cancers.

Do we know what causes MCC? What are the risk factors that patients should be aware of?

We do know some risk factors. We know that the older a person is, the more likely they are to have (MCC). The vast majority of (MCCs) occur in folks over the age of 65, with the typical age being around 74, so in the mid-70s. We believe that ultraviolet light — sunlight —plays a causative role as well. And we also believe that the immune system plays an important role. As we age and our immune system ages with us, it could be that there's simply less immune surveillance going on as well.

One thing that's very interesting about (MCC) that is still being worked out is an association with a certain virus — Merkel cell polyomavirus — that we have discovered in about 80% of (MCCs). But what's interesting about this particular virus is that it's everywhere. Almost everybody has been exposed to this virus, so we don't know why it is that some people, when exposed to this virus, will develop (MCC), whereas the vast majority of people do not. It's like many viruses that we get exposed to in everyday life. Most of us have been exposed to the human papilloma virus, which causes warts. It's just one of those viruses that's it's ubiquitous. It’s just everywhere.

How can patients be aware that they might have MCC? Are there certain lesion characteristics that they should look out for?

That's one of the more frustrating things about (MCC), is that it can look like any of the other skin cancers. It's very common for a dermatologist to see a lesion on the skin and understand that there's something abnormal here. We need to biopsy this lesion and figure out what it is. More likely than not, we're going to think that it's one of the other more common types of skin cancer, and usually we just get back a pathologic diagnosis.

(MCC) doesn't have a typical appearance, per se, but generally, they're going to be pinkish red bumps, more common in sun-exposed areas. The head and neck are the most common areas, but they can be anywhere head to toe. My general rule of thumb, as a dermatologist specializing in skin cancer, is that if you have a new skin lesion, you need to see your dermatologist to have that evaluated.

Is there any chance for it to be misdiagnosed for a different type of skin cancer?

The most important part of the biopsy is making sure you get a good representative sample, make sure the biopsy is large enough so when the pathologist analyzes it, they have sufficient material to make a diagnosis. I also recommend that, whenever possible, the specimen be examined by a specially trained pathologist called a dermatopathologist. And so dermatopathologists are individuals who have undergone additional training in pathology of the skin, so they're well equipped to recognize these rare skin tumors.

How is MCC treated?

Of course, every patient is unique with unique circumstances and unique problems. As a general rule for (MCC), there are several steps we like to take. The first is … make the diagnosis, make sure we have a correct diagnosis. And that's where both the dermatologist and the dermatopathologist play an important role.

Then the next step is we need to assess is this particular (MCC) isolated to the skin or has it gone somewhere else in the body? One of the steps that we almost always take with this disease is what's called a sentinel lymph node biopsy. And that's where a surgical oncologist will map the lymphatics and remove lymph nodes for testing. So that's the next thing we need to figure out.

And then treatment there really depends upon what we find in the lymph nodes. In general, all patients need to have the primary tumor surgically resected. As a general rule, we also like to have adjuvant radiation, so surgical removal of the tumor followed by radiation. Of course, there's always exceptions. One nice thing about (MCC) is that it does respond to radiation therapy. It's called radiosensitive. And so I've had instances where surgery was not feasible, and we've had good results with radiation alone.

As a general rule, we do sentinel lymph node biopsy, surgery and radiation. Those are the three cornerstones of treatment. If, unfortunately, the cancer has spread, then we're looking at systemic therapy, and immunotherapy is the current standard of care for (MCC) that has spread.

What type of outcomes can we expect with patients who do develop this type of skin cancer?

We have some reasonable staging data. Again, the datasets not huge because there's not tens of thousands of datapoints that we can rely upon. But generally speaking, patients are staged either clinically or pathologically. We call them pathologically staged if they've had a lymph node biopsy and we know the status of their lymph nodes. If they have not had a lymph node biopsy or no pathology done on the lymph node, then they're clinically staged. And that may just be what we see, and then we try to feel lymph nodes.

So staging is based on the size of the primary tumor. Two centimeters appears to be an important breakpoint, and then the status of their lymph nodes, or certainly once it becomes metastatic, then the prognosis is much worse.

The risk of recurrence really depends upon the size of the tumor and also the status of their lymph nodes. Those are two really important things.

Earlier we talked about the (Merkel cell polyomavirus). This is still preliminary, but it appears that people who have an antibody response to the virus — that is, their body recognizes that the virus is present and mounts a response to that — may do better than patients who do not have an antibody response to this particular virus. It plays into … the importance of the immune system in this disease.

What’s some advice you would give to patients and their caregivers?

The best piece of advice for someone with (MCC) is, if you can, try to find a group of physicians that have treated (MCC) with some frequency and understand the basic care pathway, the sentinel lymph node biopsy, followed by surgery, followed by radiation. For the vast majority of patients, that's where they need to be.

The other thing is, I would encourage them to go to a really wonderful website called MerkelCell.org. It's (managed) by some clinicians and researchers at the University of Washington. And it gives very unbiased, high-quality advice both for physicians looking to learn more about (MCC), but it's also really geared toward the (MCC) patient.

I hope everyone gets a chance to think about (MCC). I hope no one … ever gets one, but there is a chance that you or someone you know could develop one of these rare but increasingly common tumors, and having some baseline knowledge will really help you.

For more news on cancer updates, research and education, don’t forget to subscribe to CURE®’s newsletters here.