Merkel cell carcinoma

Alternate names '

Merkel cell cancer; Merkle tumors; Carcinoma, merkel cell; Cutaneous neuroendocrine carcinoma

Carcinome à cellules de Merkel

Definition

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer. It usually develops as a single, painless, bump on sun-exposed skin. The bump may be skin-colored or red-violet, and tends to grow rapidly over weeks to months. It may spread quickly to surrounding tissues, nearby lymph nodes, or more distant parts of the body.

Small spot on the left arm is Merkel-cell cancer

Merkel-cell carcinoma. Gross pathology specimen

Risk factors

Increased incidence of MCC has also been seen in people treated heavily with methoxsalen (psoralen) and ultraviolet A (PUVA) for psoriasis (3 of 1,380 patients, 0.2%), and those with chronic immune suppression, especially from chronic lymphocytic leukemia, human immunodeficiency virus, and previous solid organ transplant.

Merkel cell cancer

Other risk factors that have been associated with MCC include:

• being older than age 50
• having fair skin
• having a history of extensive sun exposure
• having chronic immune suppression (e.g. organ transplantation or HIV)

Cause

Cancer is caused by changes (mutations) in the DNA inside of cells. These mutations cause the cells to grow and divide into new cells, when they should not. The mutations that cause MCC are not inherited from a parent, but occur by chance during a person's lifetime (they are acquired, or somatic mutations). In many cases, it is not known what directly causes these mutations to occur. However, several factors are thought to increase the risk for mutations to occur - such as exposure to sunlight. Merkel cell polyomavirus is frequently involved in the development of MCC and is present in about 80% of MCC tumors tested. While the majority of people have been exposed to this virus by adulthood, it appears that the virus does not cause any symptoms except in the very rare situations in which it leads to MCC.

Inheritance

MCC does not seem to run in families.While DNA changes (mutations) found in the cells of MCC tumors can lead to MCC, these types of mutations are not inherited from a person's parents. They are referred to as somatic mutations and occur during a person's lifetime, often as random events.

Symptoms

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed

100% of people have these symptoms

• Merkel cell skin cancer

30%-79% of people have these symptoms

• Cellular immunodeficiency
• Chronic noninfectious lymphadenopathy
• Cutaneous photosensitivity(Photosensitive skin)
• Erythematous macule
• Erythematous plaque
• Regional abnormality of skin
• Skin nodule

5%-29% of people have these symptoms

• Basal cell carcinoma
• Carcinoid tumor
• Lymphoid leukemia
• Multiple myeloma
• Squamous cell carcinoma of the skin

1%-4% of people have these symptoms

• Abnormal brain FDG positron emission tomography
• Brain neoplasm
• Neoplasm of the outer ear(Outer ear tumor)

Diagnosis

Diagnosis of MCC begins with a clinical examination of the skin and lymph nodes.Following clinical exam, definitive diagnosis of Merkel cell carcinoma (MCC) requires examination of biopsy tissue to identify its histopathologic features. An ideal biopsy specimen is either a punch biopsy or a full-thickness incisional biopsy of the skin including full-thickness dermis and subcutaneous fat. On light microscopy, MCC shows basaloid tumor nests with neuroendocrine features ("salt and pepper" chromatin, scarce cytoplasm, and brisk mitotic activity).

Differential diagnosis

In addition to standard examination under light microscopy, immunohistochemistry (IHC) is also generally required to differentiate MCC from other morphologically similar tumors such as small cell lung cancer, the small cell variant of melanoma, various cutaneous leukemic/lymphoid neoplasms, and Ewing's sarcoma. Neuroendocrine molecular markers such as synaptophysin or chromogranin A are characteristic of MCC and other neuroendocrine tumors, while other markers such as PAX5 or cytokeratin 20 can distinguish MCC from these tumors.

Treatment

Treatment may include surgery, radiation therapy, and/or chemotherapy. Treatment options and prognosis depend on the location(s) and size of the cancer, whether it has just been diagnosed or has come back (recurred), and how deeply it has grown into the skin. The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Avelumab (Brand name: Bavencio): Treatment of adults and pediatric patients 12 years and older with metastatic Merkel cell carcinoma.
• Pembrolizumab (Brand name: Keytruda)pembrolizumab (Keytruda) was approved for the treatment of adult and pediatric patients with recurrent locally advanced or metastatic Merkel cell carcinoma.

Epidemiology/Etiology

In Surveillance, Epidemiology, and End Results (SEER) Program data from 1986 to 2001, the age-adjusted U.S. annual incidence of MCC tripled from 0.15 to 0.44 per 100,000, an increase of 8.08% per year. Although this rate of increase is faster than any other skin cancer including melanoma, the absolute number of U.S. cases per year is small. About 1,500 new cases of MCC were expected in the United States in 2007.

Gallery

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  Chang & Moore (2017)

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  Merkel cell carcinoma on arm

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  Merkel cell carcinoma

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  Merkelcellskarcinom

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