About one third of cases of Merkel cell carcinoma occur in patients with CLL. Although second cancers reputedly occur more commonly in patients with CLL, it is remarkably difficult to demonstrate the fact in epidemiological studies. It is only very obvious in tumors where the immune system plays a large part in the control of the tumor, like in melanoma or Kaposi's sarcoma. So the betting was always that Merkel cell carcinoma was one of those rare human tumors caused by a virus. Research published this year suggests that this guess was right.
Merkel Cell Carcinoma, also known as trabecular cancer, Apudoma of skin, or Small cell neuroepithelial tumor of the skin, is a rare and highly aggressive cancer where malignant cancer cells develop on or just beneath the skin and in hair follicles. This cancer is a type of neuroendocrine tumor, like small cell lung cancer. Once it has metastasized to the lymph nodes, the 5-year survival rate for a patient is about 50 percent. Small tumors (less than 2 cm) that have not metastasized to the lymph nodes have a 5-year survival rate of more than 90 percent, however.
It occurs most often on the face, head, and neck. It usually appears as firm, painless nodules. These flesh-colored, red, or blue tumors vary in size from 5 mm (less than a quarter of an inch) to more than 5cm (2 inches). The tumor grows rapidly. About half of all Merkel cell cancers occur on the sun-exposed areas of the head and neck, while one-third begin on the legs, and 15% occur on the arms. The cancer may also begin on other parts of the body, such as the trunk.
From initial onset, Merkel cell cancer metastasizes quickly and spreads to other parts of the body, tending towards the regional lymph nodes. The tumor tends to invade underlying subcutaneous fat, fascia, and muscle. It can also metastasize to the liver, lungs, brain or bones.
This type of cancer occurs mostly in white Caucasians between 60 and 80 years of age. It occurs about twice as often in males as in females. There are roughly 1200 new cases diagnosed a year in the United States, compared to 60,000 new cases of melanoma and over 1 million new cases of nonmelanoma skin cancer. Merkel cell cancer can be mistaken for another cancer like basal cell carcinoma, squamous cell carcinoma, malignant melanoma, lymphoma, or small cell carcinoma, or may appear to be a benign cyst. Researchers believe that exposure to sunlight or ultraviolet light may increase a person’s risk of this disease.
Immune suppression can profoundly increase one's risk of developing Merkel cell cancer. Merkel cell carcinoma occurs 13.4 times more often in people with advanced HIV as compared to the general population. Solid organ transplant recipients have similarly increased risk and so do those taking immunosuppressive drugs such as fludarabine and Campath.
A newly discovered virus called Merkel cell polyomavirus (MCV) is suspected to contribute to the development of the majority of MCC. Approximately 80% of MCC tumors have this virus integrated in a monoclonal pattern, indicating that the infection was present in a precursor cell before it became cancerous. Polyomaviruses have been known to be cancer viruses in animals since the 1950s, but this is the first polyomavirus strongly suspected to cause tumors in humans. Like other tumor viruses, most people who are infected with MCV probably do not develop MCC; it is unknown what other steps are required for the development of MCC. Ultraviolet light (sun) exposure probably contributes to MCC development in a large number of cases. MCC also occurs more frequently than expected among immunosuppressed patients, such as transplant patients, AIDS patients, those on immunosuppressive drugs and the very old.
Surgery is the usual treatment for Merkel cell cancer. The tumor is removed along with a border of healthy tissue surrounding it. Nearby, or regional, lymph nodes are often removed because they may contain cancer cells. Sometimes the doctor performs a sentinel lymph node biopsy. In this procedure, the doctor injects a dye or radioactive substance near the tumor. This material flows into the first lymph nodes where cancer is likely to spread (the sentinel nodes). These nodes are then removed and checked for cancer cells. This procedure has been demonstrated to be an important prognostic indicator. Results help dictate the use of appropriate adjuvant therapy, if necessary.
Adjuvant radiotherapy has been shown to be effective in reducing recurrence and increasing five year survival of patients with Merkel Cell Carcinoma. Patients who present with no metastases and a negative sentinel lymph node biopsy have a good prognosis when treated with surgery and radiotherapy - approximately 90% survival at five years.
Merkel cell cancer that has metastasized may respond to treatment with chemotherapy and/or radiation. This therapy usually does not cure the disease, but can be effective in shrinking the tumor if the tumor is too large to be removed, or is located in a place where removal would be difficult or dangerous.