Merkel cell cancer overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmad Al Maradni, M.D. [2]
Overview
Merkel cell cancer is a rare and highly aggressive cancer where malignant cancer cells develop on or just beneath the skin and in hair follicles. This cancer is a type of neuroendocrine tumor, like small cell lung cancer. Merkel cell carcinoma is the most serious form of skin cancer. Once it has metastasized to the lymph nodes, the 5-year survival rate for a patient is about 50 percent. A small tumor (less than 2 cm) that has not metastasized to the lymph nodes reported a 5-year survival rate of more than 90 percent; however, at the time of diagnosis of MCC the 5-year survival was 64 percent. Recurrence can occur in up to half of all patients. [1]
It occurs most often on the face, head, and neck. It usually appears as firm, painless, nodules, or tumors. These flesh-colored, red, or blue tumors vary in size from 5 mm (less than a quarter of an inch) to more than 5cm (2 inches). The tumor grows rapidly. About half of all Merkel cell cancers occur on the sun-exposed areas of the head and neck, while one-third begin on the legs, and 15% occur on the arms. The cancer may also begin on other parts of the body, such as the trunk.
From initial onset, Merkel cell cancer metastasizes quickly and spreads to other parts of the body, tending towards the regional lymph nodes. The tumor tends to invade underlying subcutaneous fat, fascia, and muscle. It can also metastasize to the liver, lungs, brain or bones.
Historical Perspective
Merkel cell polyomavirus, the pathogen responsible for Merkel cell cancer, was first discovered in 2008.[2]
Classification
Mercell cell carcinoma is classified into 3 subgroups: trabecular, intermediate, and small cell.
Pathophysiology
Causes
Merkel cell cancer is caused by Merkel cell polyomavirus (MCV) infection.
Differential Diagnosis
Merkel cell cancer must be differentiated from other skin lesions, such as basal cell carcinoma, squamous cell carcinoma, malignant melanoma, lymphoma, vascular tumors, and other benign skin tumors.
Epidemiology and Demographics
The incidence of Merkel cell carcinoma ranges from 0.15 to 0.44 per 100,000 individuals. The median age at diagnosis is approximately 65 years. Merkel cell carcinoma is more common among males and individuals of Caucasian race.
Risk Factors
Risk factors for the development of Merkel cell cancer include old age, male gender, Caucasian race, chronic exposure to sunlight, immunodeficiency, and personal history of cancer.
Screening
Screening for Merkel cell cancer is not recommended.
Natural History, Complications and Prognosis
Merkel cell carcinoma is a highly aggressive tumor with a mortality rate that approaches 30% to 40% within 3 years of diagnosis. If diagnosed early, Merkel cell cancer has a good prognosis with a 5-year survival rate of approximately 90%.
Diagnosis
Staging
The staging of Merkel cell cancer is based on the TNM staging system.
History and Symptoms
Patients with Merkel cell carcinoma usually present with a rapid growing, painless, small mass that is typically located on sun exposed area of the body.
Physical Examination
Physical exam findings of Merkel cell cancer include a firm, dome-shaped or raised, red/violaceous skin mass that appear in sun exposed areas.
Laboratory Findings
CT
CT scan is useful in detecting metastasis to organs and regional lymph nodes.
Other Imaging Findings
Positron emission tomography maybe used in staging of Merkel cell cancer.
Other Diagnostic Studies
On biopsy, Merkel cell cancer is characterized by positivity on cytokeratin-20 immunohistochemical staining. On electron microscopy, the presence of neurosecretory granules within cytoplasmic extensions is characteristics.
Treatment
Medical Therapy
The predominant therapy for Merkel cell cancer is surgical resection. Adjunctive chemotherapy and radiation may be required.
Surgery
The majority of cases of Merkel cell cancer are treated with Surgery.
Primary Prevention
Primary prevention of Merkel cell cancer includes avoidance of excessive sun exposure and use of sunscreen.
Secondary Prevention
Primary prevention of Merkel cell cancer includes avoidance of excessive sun exposure and use of sunscreen.
References
- ↑ Allen PJ, Browne WB, Jaques DP; et al. (2005). "Merkel cell carcinoma: Prognosis and treatment of patients from a single institution". Journal of Clinical Oncology. 23 (10): 2300–2309.
- ↑ Spurgeon ME, Lambert PF (2013). "Merkel cell polyomavirus: a newly discovered human virus with oncogenic potential". Virology. 435 (1): 118–30. doi:10.1016/j.virol.2012.09.029. PMC 3522868. PMID 23217622.