Merkel cell tumor


Merkel cell tumor

Description, Causes and Risk Factors:

Alternative Name: Merkel cell carcinoma (MCC), primary neuroendocrine carcinoma of the skin, trabecular carcinoma.

Merkel cell carcinoma is an aggressive neuroendocrine cutaneous neoplasm with a propensity to spread to regional lymph nodes. This aggressive skin cancer is uncommon but increasing in frequency. During 1986-2001, incidence rate tripled; average annual increase was 8%.

    MCC shares epidemiologic features with Kaposi sarcoma, a malignant tumor associated with human herpesvirus 8 infection.

  • In particular, MCC affects predominantly immunocompromised patients such as organ transplant recipients patients with B-cell lymphoid tumors and patients with AIDS. This similarity between MCC and Kaposi sarcoma may support the hypothesis of an infectious origin of MCC.

  • Sun exposure and immunodepression are the most significant risk factors. The high incidence in whites compared with blacks and the typical presence in sun damaged skin supports this theory. The co-existence of this skin tumour with other dermal neoplasia related with ultraviolet radiation has been reported. This suggests the appearance of genetic mutations that could lead to these lesions.

  • A new polyomavirus, provisionally named merkel cell polyomavirus (MCPyV), has been recently identi?ed in tumor tissue from patients with MCC. Furthermore, clonal integration of viral DNA within the tumor genome was observed in most other cases.

These tumours appear in the 7th and 8th decade of life. There is almost no gender difference. Nevertheless there is a marked difference between races. Incidence is twenty times greater in whites compared to blacks.

Management of MCC is challenging, as therapy is different in nature than for other skin malignancies and is controversial within the literature. Proper care requires coordination between dermatologists, radiation and medical oncologists, and surgeons.

Symptoms:

Symptoms of Merkel Cell Carcinoma may include:

    Growth of painless lumps in the skin.

  • Change of skin locally.

  • Mole changes their appearance.

  • There are abnormal skin growths similar to signs of other skin cancer types.

  • Lymph nodes of groin, axillae and neck being affected.

  • Solitary red nodules.

Diagnosis:

Initial diagnosis of MCC in the primary lesionby hematoxylin and eosin staining (H&E) should befurther confirmed by performing immunohistochemical(IHC) staining.The histologic diagnosis can be difficult, because with the conventional light microscopy merkel cell carcinoma can be misdiagnosed as any other poorly differentiated small cell neoplasm. Electron microscopy plays a significant role in the diagnosis of MCC for some authors, because of the possibility of recognize peripheral neurosecretory granules andneurofilaments.

Treatment:

No single standard of care exists for the treatment of this aggressive tumour. However it's accepted that the basis is surgery, completed if necessary with other therapies. Wide local excision is very important, with large free-margin recommended (2-3 cm.). Mohs micrographic surgery could be useful, because of the better local control, avoiding in some cases postexcision irradiation.

Sentinel lymph node biopsy may provide an accurate and less morbidity alternative to neck dissection for the treatment and staging of regional occult neck disease in merkel cell carcinoma. Ultraviolet radiation is the main risk factor described so the only known prophylaxis is photoprotection.

Chemotherapy is reserved for systemic disease, though the success of this treatment is limited and no chemotherapy protocol has been shown to improve survival. Chemotherapeutic regimens most often used for the treatment of merkel cell carcinoma are similar to those performed for the small cell carcinoma of the lung.

Radiotherapy alone can be used as palliative treatment with good control of primary and lymph node metastases.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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