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    Diseases
    Medically Reviewed

    Merkel Cell Carcinoma

    Overview

    Merkel cell carcinoma (MCC) is a rare but highly aggressive form of skin cancer that originates from Merkel cells, which are found in the upper layers of the skin and play a role in the sensation of touch. MCC is known for its rapid growth and high risk of spreading (metastasizing) to other parts of the body, including lymph nodes and distant organs. This cancer most commonly appears as a painless, firm, flesh-colored or bluish-red nodule on sun-exposed areas of the skin, such as the face, neck, and arms. Early detection and treatment are crucial due to its aggressive nature.

    Causes

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

    • Merkel cell polyomavirus (MCV): A common virus found in the skin is present in the majority of MCC cases. Although many people have MCV, only a few develop cancer.
    • Ultraviolet (UV) radiation: Extensive exposure to sunlight or tanning beds increases the risk of MCC, particularly in fair-skinned individuals.
    • Weakened immune system: People with weakened immunity, such as organ transplant recipients or those with HIV/AIDS, have a higher risk.
    • Older age: MCC primarily affects older adults, typically those over 65 years of age.
    • Light skin complexion: Caucasian individuals are at higher risk compared to those with darker skin tones.
    • Previous history of skin cancer: Individuals with a history of other skin cancers have a higher likelihood of developing MCC.

    Symptoms

    Merkel cell carcinoma typically presents with the following signs and symptoms:

    • Fast-growing skin nodule: A painless, rapidly enlarging lump on the skin, usually on sun-exposed areas.
    • Firm and shiny appearance: The nodule often feels firm or rubbery and has a smooth, shiny surface.
    • Color changes: Lesions may be red, pink, blue, or skin-colored.
    • No associated pain or itching: MCC lesions are typically not painful or itchy, which can delay diagnosis.
    • Lymph node swelling: In some cases, nearby lymph nodes may become enlarged due to cancer spread.

    Diagnosis

    Diagnosing Merkel cell carcinoma involves several steps:

    • Physical examination: A dermatologist or physician examines the suspicious skin lesion and evaluates for lymph node involvement.
    • Skin biopsy: A sample of the skin lesion is taken and examined under a microscope to confirm the diagnosis.
    • Immunohistochemistry: Special staining techniques help identify Merkel cell markers (e.g., cytokeratin 20).
    • Imaging tests: CT scans, MRI, or PET scans may be performed to determine if cancer has spread to lymph nodes or distant organs.
    • Sentinel lymph node biopsy: A procedure to check for cancer spread to the nearest lymph nodes.

    Treatment

    The treatment approach for Merkel cell carcinoma depends on the stage and spread of the disease:

    • Surgery: Wide local excision is often performed to remove the tumor with clear margins. Lymph node dissection may also be necessary if there is nodal involvement.
    • Radiation therapy: Frequently used after surgery to reduce the risk of local recurrence, especially in high-risk cases.
    • Immunotherapy: Immune checkpoint inhibitors (e.g., avelumab, pembrolizumab) are now standard treatments for advanced or metastatic MCC.
    • Chemotherapy: May be considered for metastatic disease, although its role is decreasing due to the success of immunotherapy.
    • Regular follow-up: Continuous monitoring for recurrence or metastasis is crucial due to the high rate of recurrence.

    Prognosis

    The prognosis for Merkel cell carcinoma depends on the stage at diagnosis and response to treatment:

    • Early-stage detection: When diagnosed early and treated promptly, the five-year survival rate is significantly better, ranging from 60% to 70%.
    • Advanced disease: MCC that has spread to lymph nodes or distant organs has a poorer prognosis, with lower survival rates.
    • High recurrence risk: MCC is known for its high likelihood of returning, particularly within the first two years after treatment.
    • Improved outcomes with immunotherapy: Recent advances in immunotherapy have improved survival rates in patients with advanced disease.

    Regular follow-ups, early diagnosis, and advancements in treatment options have improved outcomes, but Merkel cell carcinoma remains a serious condition requiring aggressive management.