Merkel cell carcinoma is a rare but serious type of skin cancer, which is also called neuroendocrine tumor of the skin. The cancer tends to growon the surface of the skin or just below and in the hair follicles. It is considered as a cutaneous (skin) neuroendocrine tumor becauseitoriginates in the hormone-producing cells that resemble nerve cells (neuroendocrine cells).
Although Merkel cell carcinoma can appear anywhere, it is mostfrequently observed in the head, neck and arms. The cancer usually develops quickly and often spreads to other parts of the body to form other cancers (metastasis).
Merkel Cell CarcinomaFrequency
About 95% Merkel cell carcinoma cases primarily affects elderly individuals aged 50 years or older. People with light skin are more affected, with an equal distribution in both sexes. Its frequency is less than 1/200 000.
Although Merkel cell carcinoma was described since 1972 by researcher Cyril Toker, studies have been conducted on it until this day. In 2008, a team of researchers has identified the existence of viral sequences within cells of this cancer (Merkel cell polyomavirus). In other subsequent studies, other scientists have confirmed this finding.
Merkel Cell Carcinoma Causes and Risk Factors
The following risk factors may increase the likelihood that a person will be diagnosed with Merkel cellcarcinoma:
- Prolonged or regular sun exposure
- Weakened immune system
- Previous administration of PUVA (psoralen + UVA)
Skin color– Merkel cell carcinoma is most commonly diagnosed in light or clear skin people agedover 50.
Another risk factor is immunosuppression (suppression of the immune system and its ability to fight infection) in organ transplant recipients or secondary to HIV infection.
Professor Paul Nghiem of the University of Washington created an acronym to allow doctors to remember Merkel cell carcinoma characteristics, and to help patients recognize risk factors associated with it, AEIOU: A because it is an asymptomatic lesion, E because it expands rapidly (spreads quickly), I for immunocompromised, O for older than 50 years old (individuals aged older than 50 years) and finally U to UV exposure and light skin.
Merkel Cell CarcinomaPrognosis
Merkel cell carcinoma is a dangerous form of cancer; the prognosis is gloomy and sombermost of the times. It is now considered more reserved than in the case of melanoma. However, the survival depends greatly on the stage of the cancer at diagnosis.
There are 4 stages in the evolution of Merkel cell carcinoma
Stage I: primary lesion is less than 2 cm,
Stage II: the primary lesion is greater than 2 cm,
Stage III: the tumor has spread to the nearby lymph node (non-aggressive metastasis),
Stage IV: the tumor has spread to distant tissue or organs (aggressive or distant metastasis).
Patients whose lymph nodes are uninfected have a survival rate at five years more than 80%, but the rate is less than 50% in case the cancer has spread to lymph node. The technique of sentinel lymphnode biopsy has clouded this prognosis; the risk of relapse is about 60% in the three years in case ofpresence of lymphatic metastases, while it is only 20% in the absence of metastasis. Although rare, some cases of spontaneous regression due to apoptosis of tumor cells have been observed.