Home/Rare Diseases/Merkel Cell Carcinoma
Rare Cancers

Merkel Cell Carcinoma

Affects approximately
About 3,000 new cases per year in the U.S.; incidence has tripled over the past 2 decades

Also known as: MCC, neuroendocrine carcinoma of the skin, trabecular carcinoma

Merkel Cell Carcinoma

About Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare neuroendocrine skin cancer with aggressive behavior and high recurrence rates. It arises from Merkel cells, specialized mechanoreceptors in the basal layer of the epidermis. MCC is associated with two distinct etiologic pathways: Merkel cell polyomavirus (MCPyV) integration (80% of cases) and ultraviolet radiation-induced DNA damage (virus-negative MCC, which typically has very high mutational burden). MCC typically presents as a rapidly growing, painless, dome-shaped nodule on sun-exposed skin. The mnemonic AEIOU describes its features: Asymptomatic, Expanding rapidly, Immune suppression, Older age, UV-exposed skin. Despite its small primary tumor size, MCC has a high propensity for lymph node metastasis and distant spread. Treatment involves wide surgical excision with sentinel lymph node biopsy, often followed by radiation therapy. For advanced or metastatic MCC, checkpoint immunotherapy (avelumab or pembrolizumab) has shown remarkable response rates, transforming outcomes for this disease.

Common Symptoms

  • A firm, painless, dome-shaped nodule on the skin
  • Rapidly growing skin lesion, often red, blue, or purple
  • Usually appears on sun-exposed areas (head, neck, arms)
  • Nodule may be shiny and flesh-colored to red
  • Rarely causes pain or itching in early stages
  • May be mistaken for a cyst or other benign skin growth

Who It Affects

Primarily affects older adults (median age at diagnosis ~75-80 years), with strong association with chronic sun exposure and fair skin. Significantly more common in immunosuppressed individuals (organ transplant recipients, HIV patients, chronic lymphocytic leukemia patients). About 3-5 times more common in men than women. Merkel cell polyomavirus (MCPyV) is found in ~80% of tumors.

Getting Involved in Clinical Trials

Clinical trials are evaluating novel immunotherapy combinations, intralesional therapies, and targeted agents for MCC. The checkpoint inhibitor avelumab was the first FDA-approved treatment specifically for metastatic MCC. For localized disease, trials are exploring whether neoadjuvant immunotherapy before surgery improves outcomes. Given MCC's rarity, referral to a cancer center experienced in treating MCC is highly recommended. Ask about PD-L1 testing and MCPyV status of your tumor, as these may influence prognosis and treatment decisions. The MCC Patient Registry and patient advocacy groups can connect you to specialists and trials.

Trusted Sources

Active Clinical Trials for Merkel Cell Carcinoma

Finding trials for Merkel Cell Carcinoma...

Related Rare Cancers Conditions

Rare Cancers

NTRK Fusion Cancer

NTRK fusion cancers are a group of rare tumors driven by gene fusions involving 1 of 3 NTRK genes (NTRK1, NTRK2, or NTRK...

Rare Cancers

Cholangiocarcinoma

Cholangiocarcinoma is a rare and aggressive cancer that forms in the bile ducts, the thin tubes that carry digestive flu...

Rare Cancers

Mesothelioma

Mesothelioma is a rare, aggressive cancer that develops in the mesothelium, the thin layer of tissue covering most inter...