- What is Merkel cell carcinoma?
Merkel cell carcinoma (MCC) is a rare, aggressive type of skin cancer that
forms on or just under the skin. It is also called primary small cell
carcinoma
of the skin, trabecular carcinoma, APUDoma, neuroendocrine
carcinoma, endocrine
carcinoma, or primary undifferentiated
tumor
of the skin (1). MCC is believed to start in neuroendocrine
cells called Merkel cells. These cells release hormones
into the blood
when stimulated by the nervous
system. They migrate from part of the nervous system called the neural
crest to the skin (2). Merkel cells are believed to play
a role in making the skin sensitive to touch (3).
- How often does Merkel cell carcinoma occur?
Approximately 1,200 new cases of MCC are diagnosed
in the United States each year (4), compared with almost
60,000 new cases of melanoma
and more than 1 million new cases of nonmelanoma
skin cancer. The incidence
of MCC has been rising, with a 3-fold increase between 1986 and 2001 (4).
Most patients diagnosed with MCC are over age 50 at diagnosis (the average
age is 69), with only 5 percent of cases diagnosed in those under age 50 (5).
MCC is more common in white people than in other racial/ethnic groups. Some
cases have been reported in Japanese people, but very few have been seen in
black people (6).
- What are the possible causes of Merkel cell carcinoma?
The exact cause of MCC is unknown, but it appears to be linked to sun exposure
and immunosuppression (suppression of the body's immune
system and its ability to fight infections
or disease) (2). Sun exposure as a risk
factor for MCC is supported by data that show a rise in incidence corresponding
with the solar UVB index (scale indicating the intensity of solar ultraviolet-B
(UVB) radiation at noon for a particular location) (6).
MCC has been linked to conditions such as HIV
infection, chronic
lymphocytic leukemia, Hodgkin
lymphoma (cancer of the lymph
system), ectodermal dysplasia
(a disease involving abnormal
tissue
development), and Cowden disease (a disease in which masses of abnormal but
benign
tissues grow in multiple sites in the body). Other possible causes include
exposure to arsenic
and treatment for psoriasis
that uses psoralens (a medication that causes the skin to become sensitive
to light) and ultraviolet-A light (PUVA) (2).
- What are the symptoms
of Merkel cell carcinoma?
The most common symptom of any skin cancer, including MCC, is a change in
the skin, especially a change in an existing mole
or a new growth. MCC appears as a firm, painless lump within the skin that
may resemble a cyst
but is fixed; i.e., cannot be moved. The lump is usually less than 2 cm (about
¾ inch) in size and can be red, pink, or blue-violet. MCC is different
from other skin cancers in that it grows rapidly over a few weeks or months
(5).
- Where does Merkel cell carcinoma develop?
MCC is usually found on sun-exposed areas of the body. Fifty percent of
cases occur on the head and neck, especially around the eye and on the eyelid
(1). Forty percent of cases occur on the arms and legs (2).
MCC has also been found on the trunk and other areas of the skin that are
not usually exposed to the sun (1).
- How is Merkel cell carcinoma diagnosed and staged?
The doctor may use the following procedures and tests to diagnose MCC. Some
of these tests are also used to help determine the stage
of the disease. Stage is a description of the extent of cancer.
- A biopsy
is the removal of cells or tissue from a tumor for examination
by a pathologist.
The pathologist may study tissue samples under a microscope or perform other
tests on the cells or tissue. Biopsies are used for both diagnosis and staging.
The surgeon
may also remove lymph
nodes (small, round organs
that trap cancer cells, bacteria,
or other harmful substances) to help determine the stage of the disease.
- Sentinel
lymph node (SLN) biopsy is a procedure in which the sentinel
lymph node is removed and examined under a microscope to determine whether
cancer cells are present. The sentinel lymph node is the first lymph node
to which cancer is likely to spread from the primary
tumor. SLN biopsy is used to help determine the stage of the disease.
SLN biopsy may cause fewer side
effects than standard lymph node removal because fewer lymph nodes are
taken out.
- Immunohistochemistry (staining of cells with agents
that react with antibodies
on the surface of cancer cells) is a laboratory technique used to tell the
difference between MCC and other types of cancer (2).
- Computed
tomography (CT), a procedure that uses special x-ray
equipment to obtain cross-sectional pictures of the body, can distinguish
MCC from small
cell lung cancer and show whether the disease has metastasized
(spread) to other parts of the body (5).
- In an octreotide
scan (sometimes called Somatostatin
Receptor Scintigraphy or SRS), the doctor injects
a small amount of a radioactive
drug into a vein. The drug travels through the bloodstream and attaches
to tumor cells. A machine called a scanner
detects the radioactive material and creates scans
(pictures) showing where the tumor cells are located in the body. For MCC,
this test can be used for both diagnosis and staging (5).
- A PET
scan uses radioactive sugar, which is absorbed by cancer cells
and appears as dark areas on the scan. It can be used for both diagnosis
and staging of MCC.
- How is Merkel cell carcinoma treated?
Surgery is the most common treatment for MCC. Surgery with wide margins
(a large border of healthy tissue removed with the tumor) is the recommended
treatment for MCC. Mohs
micrographic surgery, a technique in which individual layers of tissue
are removed and examined under a microscope until all cancerous tissue has
been removed, may be used instead of traditional surgery with wide margins.
Mohs micrographic surgery may be a good alternative for MCC tumors on highly
visible areas such as the face, and in areas where the surgeon would not be
able to obtain wide margins (5).
The surgeon may remove lymph nodes to help stage the disease or to prevent
recurrence
(cancer coming back). The patient may also receive adjuvant radiation
therapy (treatment given after the primary therapy) to decrease the chance
of recurrence. Chemotherapy
is the usual treatment if the disease has spread beyond the lymph nodes to
areas that are not treatable by radiation therapy.
Supportive
care is treatment given to improve the quality
of life of patients who have a serious or life-threatening disease, such
as cancer. It prevents or treats as early as possible the symptoms of the
disease, side effects caused by treatment of the disease, and psychological,
social, and spiritual
problems related to the disease or its treatment. For example, anticancer
drugs such as carboplatin
and etoposide
may be given to relieve symptoms in some patients with MCC. Radiation may
be used to relieve pain from MCC that has metastasized to the brain or bones,
and to reduce discomfort from skin problems associated with MCC (2).
Additionally, meeting with a social
worker, counselor, or member of the clergy
can be helpful to those who want to talk about their feelings or discuss their
concerns. A social worker can often suggest resources for help with recovery,
emotional support, financial aid, transportation, or home care.
- Are clinical trials (research studies) available? Where
can people get more information about clinical trials?
Yes. The National
Cancer Institute (NCI), a component of the National
Institutes of Health, is sponsoring clinical trials that are designed
to find new treatments and better ways to use current treatments. Before any
new treatment can be recommended for general use, doctors conduct clinical
trials to find out whether the treatment is safe for patients and effective
against the disease. Participation in clinical trials may be a treatment option
for patients with MCC.
People interested in taking part in a clinical trial should talk with their
doctor. Information about clinical trials is available from the NCI's Cancer
Information Service (CIS) (see below) at 1– 800– 4–
CANCER and in the NCI booklet Taking Part in Cancer Treatment Research
Studies , which can be found at http://www.cancer.gov/publications
on the Internet. This booklet describes how research studies are carried out
and explains their possible benefits and risks. Further information about
clinical trials is available at http://www.cancer.gov/clinicaltrials
on the NCI's Web site. The Web site offers detailed information about specific
ongoing studies by linking to PDQ®,
the NCI's comprehensive cancer information database. The CIS also provides
information from PDQ.
- What is the prognosis
for patients with Merkel cell carcinoma?
Prognosis describes the likely course and outcome of a disease—that
is, the chance that a patient will recover or have a recurrence. The prognosis
for MCC patients depends greatly on the stage of the disease at the time of
diagnosis. If the tumor is small (less than 2 cm or about ¾ inch) and
cancer cells have not spread to the lymph nodes, the 5-year survival
rate is more than 90 percent. Patients with MCC that has spread to the
lymph nodes have a 5-year survival rate of about 50 percent. Overall 5-year
survival for patients diagnosed with MCC is 64 percent (7),
but half of patients with advanced MCC will live only 9 months (2).
The disease recurs in about 50 percent of patients (7).
It is important to keep in mind, however, that these statistics are averages
based on large numbers of patients. Statistics cannot be used to predict what
will happen to a particular patient because each person's situation is unique.
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