Carcinoma, merkel cell

= =Carcinoma, Merkel Cell== Carcinoma, Merkel Cell, also known as Merkel Cell Carcinoma (MCC), is a rare and aggressive form of skin cancer. It originates from the Merkel cells, which are found at the base of the epidermis and are associated with the sense of touch. This type of cancer is known for its rapid growth and potential to metastasize.

Epidemiology

Merkel Cell Carcinoma is a rare disease, with an incidence of approximately 0.7 cases per 100,000 people per year in the United States. It predominantly affects older adults, with the majority of cases occurring in individuals over the age of 65. There is a higher prevalence in Caucasian populations, and it is slightly more common in males than females.

Etiology

The exact cause of MCC is not fully understood, but several risk factors have been identified:

• Ultraviolet (UV) Exposure: Prolonged exposure to UV radiation from the sun or tanning beds is a significant risk factor.
• Merkel Cell Polyomavirus (MCPyV): This virus is found in approximately 80% of MCC tumors, suggesting a strong association.
• Immunosuppression: Individuals with weakened immune systems, such as organ transplant recipients or those with HIV/AIDS, are at increased risk.

Pathophysiology

Merkel Cell Carcinoma arises from the uncontrolled proliferation of Merkel cells. These cells are neuroendocrine in nature and are located in the basal layer of the epidermis. The cancer is characterized by small, round, blue cells on histological examination, and it often expresses neuroendocrine markers such as chromogranin and synaptophysin.

Clinical Presentation

MCC typically presents as a painless, firm, red or violet nodule on sun-exposed areas of the skin, such as the face, neck, or arms. The lesion may grow rapidly over weeks to months. Due to its aggressive nature, early detection and treatment are crucial.

Diagnosis

Diagnosis of Merkel Cell Carcinoma involves:

• Biopsy: A skin biopsy is performed to obtain a tissue sample for histological examination.
• Immunohistochemistry: Staining for markers such as cytokeratin 20 (CK20) in a perinuclear dot pattern helps confirm the diagnosis.
• Imaging: CT or PET scans may be used to assess the extent of the disease and detect metastasis.

Treatment

The treatment of MCC depends on the stage of the disease and may include:

• Surgery: Wide local excision with sentinel lymph node biopsy is the primary treatment for localized MCC.
• Radiation Therapy: Often used as an adjuvant treatment to reduce the risk of recurrence.
• Chemotherapy: Used in cases of advanced or metastatic MCC, although its effectiveness is limited.
• Immunotherapy: Agents such as avelumab and pembrolizumab have shown promise in treating advanced MCC by targeting the PD-1/PD-L1 pathway.

Prognosis

The prognosis for Merkel Cell Carcinoma varies based on the stage at diagnosis. Early-stage MCC has a better prognosis, with a 5-year survival rate of approximately 60-70%. However, advanced or metastatic MCC has a poorer prognosis, with a 5-year survival rate of less than 20%.

Prevention

Preventive measures include minimizing UV exposure by wearing protective clothing and using sunscreen, as well as regular skin examinations for early detection of suspicious lesions.

See Also

• Skin Cancer
• Neuroendocrine Tumors
• Immunotherapy

NIH genetic and rare disease info

• NIH info on Carcinoma, merkel cell

Carcinoma, merkel cell is a rare disease.