Merkel Cell Carcinoma

A rare but aggressive skin cancer that needs prompt, specialized care

Medically reviewed by Dr. Steven Q. Wang, MDLast reviewed

Bring a printable list of questions to your appointment, or share this page with someone who needs it.

Download discussion guide (PDF)

What is Merkel Cell Carcinoma?

Merkel cell carcinoma (MCC) is a rare neuroendocrine skin cancer that arises near the nerve endings at the base of the outer skin layer. Only about 3,000 cases are diagnosed in the United States each year, but the number is rising — and MCC is far more likely than basal cell or squamous cell carcinoma to spread to lymph nodes and distant organs.

Two main factors drive it: the Merkel cell polyomavirus, found in roughly 80% of tumors, and long-term ultraviolet (UV) damage. It is strongly linked to being over age 50, having fair skin, and having a weakened immune system.

MCC often looks deceptively harmless — a painless, firm, fast-growing, shiny bump that may be skin-colored, red, or bluish-purple, usually on sun-exposed skin of the head, neck, or arms. Because it can move quickly, early detection and treatment by a coordinated team of specialists make a real difference in outcomes.

Need More Information?

Ask questions and get clear, trusted answers — instantly.

Chat with the Navigator

Key Topics

In-depth guides on these topics are being prepared to help you understand a Merkel cell carcinoma diagnosis and its treatment:

How is Merkel cell carcinoma diagnosed and staged?
Biopsy, immunostains, imaging, and what the stage means for your plan
What the AEIOU warning signs mean
The five features that help doctors spot MCC early
Merkel cell polyomavirus and immune suppression — why MCC develops
How a common virus and a weakened immune system contribute to the disease
Treatment options: surgery, radiation, and immunotherapy
How the main treatments are combined and sequenced
Why sentinel lymph node biopsy is routine for MCC
Checking the lymph nodes even when they feel normal
Follow-up care and monitoring for recurrence
Visit schedules, scans, and what to watch for after treatment
Advanced or metastatic MCC and checkpoint immunotherapy
Options when MCC has spread, including avelumab and pembrolizumab

Warning Signs

Doctors use the mnemonic AEIOU to describe the features that most often accompany Merkel cell carcinoma:

  • •Asymptomatic — a lump that does not hurt or itch
  • •Expanding rapidly — noticeably larger over a few weeks
  • •Immune suppression — organ transplant, chronic leukemia or lymphoma, or HIV
  • •Older than 50 years of age
  • •UV-exposed site on a person with fair skin
  • •A firm, dome-shaped, shiny nodule — red, pink, violet, or skin-colored — most often on the head, neck, or forearms

Any new bump that grows quickly, or a spot your dermatologist cannot readily explain, should be biopsied without delay.

Risk Factors

  • •Age over 50, with risk rising sharply after 70
  • •Fair skin with heavy lifetime sun exposure
  • •A weakened immune system — organ transplant, chronic lymphocytic leukemia or lymphoma, HIV
  • •Prior exposure to the Merkel cell polyomavirus
  • •A history of other skin cancers
  • •Past PUVA (psoralen plus UVA) light therapy
  • •Male sex

Prevention & Early Detection

  • •Apply broad-spectrum SPF 30+ sunscreen daily and reapply every 2 hours outdoors
  • •Wear sun-protective clothing and a wide-brimmed hat
  • •Avoid peak sun hours (10am–4pm) and never use tanning beds
  • •Examine your skin monthly and have any new or fast-growing bump checked promptly
  • •See a dermatologist for a full skin exam at least yearly
  • •If your immune system is suppressed, ask about more frequent skin checks

Treatment Options

Merkel cell carcinoma is usually treated by a team that includes dermatology and surgical, radiation, and medical oncology. The plan depends on the size and location of the tumor and whether it has reached the lymph nodes or beyond:

  • •Wide local excision: Surgically removing the tumor with a margin of healthy skin; Mohs surgery is sometimes used in cosmetically sensitive areas
  • •Sentinel lymph node biopsy: A standard part of MCC staging, done even when the lymph nodes feel normal, because microscopic spread is common
  • •Radiation therapy: MCC is very sensitive to radiation; it is often given to the tumor site and nearby lymph nodes after surgery, and can be the main treatment when surgery is not possible
  • •Lymph node treatment: Surgical removal of the lymph nodes and/or radiation to that area if cancer is found there
  • •Immunotherapy: Immune checkpoint inhibitors such as avelumab, pembrolizumab, or nivolumab for advanced, recurrent, or metastatic disease
  • •Chemotherapy: Once the mainstay for metastatic MCC, now largely replaced by immunotherapy but still an option in select cases
  • •Clinical trials: Studies of new drugs and combinations are an important option worth asking about at every stage

Printable Discussion Guide

Every question from the topics above, collected into one printable checklist — with a checkbox and space for notes beside each, and header fields for your appointment date and doctor's name.

Download the complete Merkel cell carcinoma discussion guide (PDF)

Need More Information?

Chat with our AI guide for personalized information about Merkel cell carcinoma

Chat with the Navigator