Merkel Cell Carcinoma: Explaining the Rare and Dangerous Skin Cancer

Receiving a diagnosis of Merkel cell carcinoma (MCC) can feel overwhelming, but understanding the roadmap ahead is the first step in managing this disease. This overview is designed to help you navigate your journey and prepare for meaningful conversations with your oncology team.

Overview: A Rare but Rising Concern

Merkel cell carcinoma is a rare and aggressive form of neuroendocrine skin cancer. While it accounts for a small fraction of all skin cancer cases, its impact is significant. According to recent data, the incidence of MCC is rising sharply in the United States, growing nearly twice as fast as melanoma and six times faster than most other solid tumors.

“This is a cancer of older adults,” Dr. Manisha Thakuria, director of the Merkel cell carcinoma clinic at the Dana-Farber Cancer Institute and assistant professor of dermatology at Harvard Medical School, told CURE in 2023. “So, the average age of a person with Merkel cell carcinoma is probably about 74, 75, depending on what study you look at. And we also have, increasingly, a population where patients are immunosuppressed for various reasons.

“So, although the majority of patients with Merkel cell carcinoma are not actually immunosuppressed — only about 10% of patients with Merkel cell carcinoma are classically immunosuppressed in a way that we can measure, like they take medications that bring down their immune system for common diseases like rheumatoid arthritis or psoriatic arthritis, or they might be immunosuppressed because of (being) post-transplant so they take medicines again to suppress their immune system for that, and then certain blood cancers can also immunosuppress a patient. And so, certainly there they are over-represented, that group is over-represented, in Merkel cell carcinoma patients versus the normal population.”

The cancer typically develops in the epidermis — the top layer of the skin — appearing as a firm, painless, flesh-colored or bluish-red nodule. Unlike more common skin cancers like basal cell or squamous cell carcinoma, MCC grows with startling speed and has a high propensity for metastasis, or spreading to other parts of the body, particularly the lymph nodes.

Risk factors include long-term ultraviolet (UV) exposure, fair skin and a weakened immune system. Additionally, about 80% of MCC tumors are linked to the Merkel cell polyomavirus (MCPyV), a common virus that usually remains dormant but can trigger cancer in certain individuals as their immune surveillance naturally declines with age.

Diagnosis and Staging

Because MCC can be two to three times more likely to recur than melanoma, a timely and accurate diagnosis is critical. Your medical team will likely use a combination of the following:

• Physical Exam: A thorough skin check and palpation of your lymph nodes to look for swelling or firm bumps.
• Skin Biopsy: A sample of the growth is examined by a pathologist. MCC can be difficult to diagnose because its cells resemble other "small blue cell" tumors, making specialized pathology essential.
• Sentinel Lymph Node Biopsy (SLNB): This is considered a vital step for nearly all patients. Because MCC spreads early, the SLNB identifies the first lymph node(s) where cancer cells might travel. Finding microscopic spread here can change your treatment plan significantly.
• Imaging Tests: CT, PET/CT or MRI scans are used to determine if the cancer has spread beyond the primary site to distant organs like the liver or lungs.

Treatment Options

The treatment landscape for MCC has evolved rapidly in the last decade, shifting from a reliance on chemotherapy to more effective, targeted approaches. Your plan will typically involve a multidisciplinary team:

• Surgery: The primary tumor is removed along with a "safety margin" of healthy tissue. For early-stage cases, surgery may be the first and most important step.
• Radiation Therapy: MCC is highly "radiosensitive." Radiation is often used after surgery to kill any microscopic cells left behind, or as a primary treatment for patients who cannot undergo surgery.
• Immunotherapy: This is now the standard of care for advanced or metastatic MCC. Drugs known as checkpoint inhibitors (such as avelumab or pembrolizumab) help the immune system recognize and destroy cancer cells. This therapy has significantly improved survival rates in recent years.
• Chemotherapy: While once the go-to for advanced MCC, chemotherapy is now often reserved for cases where immunotherapy isn't an option. It can shrink tumors quickly but rarely provides long-term control.

Side Effects to Watch For

Understanding potential side effects is key to maintaining your quality of life. Common effects include:

• Surgical Effects: Swelling (lymphedema), particularly if lymph nodes were removed, and localized pain or scarring.
• Radiation Effects: Skin redness (similar to a severe sunburn), fatigue, and changes in skin texture.
• Immunotherapy Effects: These drugs can cause the immune system to attack healthy tissue, leading to inflammation in the lungs, thyroid, or bowels. It is vital to report any new fatigue, cough, or digestive changes to your team immediately.
• Chemotherapy Effects: Typical issues include hair loss, nausea, and a temporary drop in white blood cell counts, which increases your risk of infection.

Conclusion

While the rising incidence of Merkel cell carcinoma is a concern for public health, the outlook for individual patients has never been better. Advances in immunotherapy have stabilized mortality rates and provided new hope for those with advanced disease.

The key to a successful journey is early detection and a proactive partnership with a specialized care team. Stay curious and vocal; your oncologists are there to translate complex data into a personalized plan that honors your health goals. By understanding the aggressive nature of this cancer and the modern tools available to fight it, you can take control of your care from day one.

References

“Cases of Merkel Cell Carcinoma, ‘a Cancer of Older Adults’ are Rising,” by Alex Biese. CURE; https://www.curetoday.com/view/cases-of-merkel-cell-carcinoma-a-cancer-of-older-adults-are-rising

Editor's note: This article is for informational purposes only and is not a substitute for professional medical advice, as your own experience will be unique. Use this article to guide discussions with your oncologist. Content was generated with AI and reviewed by a human editor.

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