Merkel Cell Carcinoma Health Article

Definition

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.