Merkel cell carcinoma (MCC) is a rare form of cancer that develops on, or just beneath, the skin and in hair follicles.
Description
Merkel cells are cells that lie in the middle layers of the skin. These cells are organized around hair follicles and are believed to act as some type of touch receptors. MCC begins in these cells.
MCC usually appears as firm shiny skin lumps, or tumors. These tumors are painless and can range in size from less than a quarter of an inch (0.6 cm) to over two inches (5.1 cm) in diameter. They may be red, pink, or blue. Tumors generally first appear on the head and neck and less frequently on other sun-exposed parts of the body.
MCC is very aggressive, it spreads very rapidly, and it often invades other tissues and organs (metastasizes). The most common sites of metastasis of MCC are the lymph nodes, liver, bones, lungs, and brain. Metastasis to the lymph nodes generally occurs within seven to eight months after the first skin tumors appear. Nearly half of all people affected with MCC will develop systemic metastases within 24 months, and 67% to 74% of these people will die within five years.
Local recurrence of MCC after the removal of the primary tumor occurs in approximately one-third of all patients and is usually apparent within four months.
Several other names have been used to describe MCC, among these are: anaplastic carcinoma of the skin, apudoma, endocrine carcinoma of the skin, neuroendocrine carcinoma of the skin (NEC), primary small-cell
carcinoma of the skin, primary undifferentiated carcinoma of the skin, and trabecular cell carcinoma. The two most commonly used names are MCC and NEC.
Demographics
MCC is seen almost exclusively in Caucasians. It affects males and females equally. It generally develops between the ages of 60 and 80, but it has been seen in a child as young as seven and a woman of 97.
By early 2001, only approximately 600 cases of MCC had been described in the medical literature. The number of new cases of MCC is expected to rise as the average life span continues to increase, exposure to the sun remains high, and MCC becomes more recognized by medical practitioners.
Causes and symptoms
The cause of MCC has not been positively identified. But, in early 2001, it is believed to be caused by the skin damage associated with exposure to ultraviolet light from the sun.
The only symptom of primary MCC is the appearance of the characteristic tumors in the skin. Lymph node metastases show enlarged, firm, lymph nodes in the region of the primary tumor. Other systemic metastases show as masses in the affected organs. The location of the primary tumor is not related to the location of these systemic metastases.
Diagnosis
The diagnosis of MCC is performed by examining and testing a biopsy of the tumor. MCC is difficult to differentiate from several other forms of abnormal tissue growth (neoplasms). This diagnosis cannot be made just
by examining the tumor cells under a microscope. It is done by performing a variety of chemical tests on these cells. Testing must be performed to make sure this is not metastatic oat-cell (lung) cancer.
Treatment team
MCC is generally first identified by a microbiologist who examines a biopsy sample. Most MCC tumor removals are performed by dermatologists. Post-operative radiation treatments are generally ordered by the dermatologist and performed by a radiation therapist under the direction of a radiologist and/or a radiation physicist.
Because of the rapid and possibly invasive nature of MCC, patients are generally referred to a physician specializing in cancer (oncologist) to ensure that the disease has not spread to other parts of the body.
Clinical staging, treatments, and prognosis
MCC is classified into three clinical stages. Stage I MCC is defined as a disease that is localized to the skin. Stage II MCC is characterized by a spreading of the disease to the lymph nodes that are near the primary skin tumor or tumors. Stage III MCC is characterized by systemic metastases.
Treatment of stage I MCC involves wide local excision and follow-up radiation therapy. Wide local excision is a procedure in which the tumor and a small area of the surrounding healthy tissue are surgically removed. Since MCC is so aggressive, all patients are considered to be at high risk for recurrence and metastasis. For this reason, all patients will undergo radiation therapy of the lymph nodes near the site of the primary tumor that was removed. A technique called lymphoscintigraphy is used to determine the precise location of the lymph nodes that are most likely to be affected.
Treatment of stage II MCC is the same as for stage I MCC with the additional removal of the affected lymph nodes.
Treatment of stage III MCC is generally chemo-therapy. But, because the number of known cases of MCC is relatively small, there is no generally prescribed chemotherapy regimen. It has been treated with etopo-side, cisplatin, and fluorouracil with varying degrees of success.
The prognosis for patients affected with MCC is generally poor. Half will have a recurrence within two years and one-third will develop systemic involvement (stage III). The average time span from diagnosis of stage III MCC to death is eight months. The two-year survival rate for people affected with MCC is approximately 50%. Women appear to have a better survival rate than men.
Alternative and complementary therapies
Naturopathic remedies believed by some to be beneficial in the prevention of skin cancers include regular cleansing by fasting, enema, or herbal supplements. Many naturopaths also recommend a daily scrubbing of the skin with a sauna brush prior to bathing to increase circulation. Vitamins A, C, and E, as well as zinc, are believed by some to be essential supplements to a high fiber diet in the prevention of skin damage. However, these remedies have not been proven effective in treating Merkel cell tumors. Traditional medical treatments which have succeeded include surgery, radiation therapy, chemotherapy, and rare success with stem cell transplant.
Coping with cancer treatment
The radiation therapy necessary for follow-up treatment after MCC tumor removal can become stressful for some patients. Additionally, most of these cancers occur in the head and neck region, and their removal can be very disfiguring. It is important that all patients receive adequate counseling and other psychological support prior to and during such treatments.
Clinical trials
In early 2001, there were three clinical studies enrolling patients in the United States. One was a phase I dosage tolerance test of the chemotherapy drug indium in 111 pentetreotide. The other two were phase II studies on the effectiveness of the chemotherapy drugs irinotecan and antineoplastons A10 and AS2-1. All three of these studies are aimed primarily at patients with stage III MCC or other inoperable neuroendocrine tumors.
Prevention
Because MCC is believed, at least in some cases, to be caused by long-term exposure to ultraviolet light, it may possibly prevented by avoiding sun exposure when possible and by wearing a PABA containing sunscreen daily.
Special concerns
MCC is very aggressive and can metastasize quickly. For these reasons, medical treatment needs to be sought quickly when MCC is suspected. Recurrence of MCC, either on the skin or in the lymph nodes or other bodily organs, is quite common. Therefore, it is extremely important that all MCC patients, even if they believe that they have no symptoms, have follow-up examinations monthly for at least two years after they have finished their initial radiation treatments.
Resources
BOOKS
Kenet, Barney J., and Patricia Lawler. Saving Your Skin: Pre vention, Early Detection, and Treatment of Melanoma and Other Skin Cancers. New York: Four Walls Eight Win dows, 1998.
ORGANIZATIONS
The Skin Cancer Foundation. 245 Fifth Ave., Suite #1403, New York, NY 10016. (800) SKIN-490. <http://www.skincancer.org>.
