Merkel cell carcinoma is an uncommon highly aggressive skin cancer with neuroendocrine properties. The cancer is highly fatal with approximately 33% of patients dying of it and about 33% having loco-regional metastases at the time of diagnosis. It is more common in elders with a median age of 76 years and only 12% of people affected <60 years of age. It is also more common in white people as compared to black, Asian or Hispanic people. Merkel cell carcinoma is frequently seen in elders with chronically sun-exposed skin and patients often have a history of other skin cancers (basal cell carcinoma, squamous cell carcinoma) with associated sun exposure. It is also associated with viral etiology (human polyomavirus 5) and is frequently seen in patients with immunosuppression (leukemia, lymphoma, HIV infection, organ transplantation).(1)
The staging of Merkel cell carcinoma is done based on the clinical presentation. It includes:
Stage 0: in situ
Stage I: a localized disease with primary lesion ≤2 cm
Stage II: a localized disease with primary lesion >2cm
Stage III: nodal spread
Stage IV: metastatic disease beyond the local nodes
The survival of the patient is dependent on the stage of the initial diagnosis. The 5-year survival of stage I Merkel cell carcinoma is 62.8%, 34.8-54.6% for stage II, 26.8-40.3% for stage III, and 13.5% for stage IV. The local or distant recurrence is most common within the first 2-3 years of initial diagnosis and patients whose recurrence has not occurred within 3 years are at reduced risk of recurrence.(1)
Is There A Surgery For Merkel Cell Carcinoma?
The primary step in the treatment of Merkel cell carcinoma is surgical excision of the localized lesion. Since the recurrence rate of Merkel cell carcinoma is very high, it is also important to have an optimal surgical margin that ranges from 1-3 cm whenever feasible. Even after wide local excision, the rate of local recurrence for the cancer is around 25-40%. Another surgical option is Mohs micrographic surgery (MMS) that provides an advantage of complete peripheral and deep histologic margin control along with sparing the healthy tissue margin. The reported local recurrence after MMS is around 5-22%. It is also important to perform a sentinel lymph node biopsy before surgical excision of cancer, either with wide local excision or MMS.(2)
Sentinel lymph node biopsy should be considered for all the patients with Merkel cell carcinoma as about 25-30% of patients with negative clinical lymphadenopathy have positive lymph node pathology. It is also an important prognostic indicator with about 50-62% having 5-year survival rate who are positive for sentinel lymph node biopsy and 60-80% for negative sentinel lymph node biopsy.(2)
Radiation monotherapy is an option for patients who are not good surgical candidates; however, the results with radiation monotherapy are inferior to complete surgical excision of the lesion as the chances of distant recurrence increases and the overall survival rates decrease. Adjuvant radiotherapy also improves the overall survival of patients with localized tumor.(2)
Chemotherapy (cisplatin, etoposide, cyclophosphamide, and doxorubicin) is associated with a high risk of toxicity and adjuvant chemotherapy has not shown any improvement in survivals of patients with Merkel cell carcinoma. However, immunotherapy (pembrolizumab, avelumab, ipilimumab) has shown positive results in patients with Merkel cell carcinoma.(2)
Signs And Symptoms Of Merkel Cell Carcinoma
Merkel cell carcinoma is a fast-growing, solitary, cutaneous or subcutaneous mass that is mostly found on sun-exposed areas (head and neck region). It is mostly asymptomatic and red-to-violet colored nodule and is confused with benign lesions as ulceration is not common. The tumor can also present as multiple growths at different sites of the body. Since the presentation of cancer is not specific, the diagnosis is usually delayed; therefore, the acronym AEIOU for asymptomatic, expanding rapidly, immunosuppressed, >50 years of age, and UV-exposed is quite relevant for initial diagnosis. However, the confirmatory diagnosis is done through biopsy.(1)
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