MCC is a rare cutaneous neoplasm of the elderly population with estimated 470 new cases in the United States each year; this incidence figure compares with 31,000 new cases of melanoma annually. Although most studies show a male predominance, with SEER data suggesting a ratio of 2.3:1, other case series demonstrate a slightly higher incidence in women.MCC is a disease of the elderly with an average age at the time of diagnosis of 69 years; only 5% of all reported patients have been diagnosed below the age of 50 years.

Clinical Presentation
At the time of diagnosis, patients typically present with a flesh-colored, red, or blue, firm, nontender intracutaneous mass that has grown rapidly over a few weeks to months and may ulcerate.Most commonly, the tumor is nodular but may also have a plaque-like appearance . Tumor size ranges from 2 to 200 mm but is most commonly less than 20 mm. It affects primarily the sun exposed areas of the skin, with approximately 50% of all tumors occurring in the face and neck; 40% appear on the extremities, and 10% on the trunk and genitals.In the face, the eyelids are involved frequently. Rare occurrences in sun-protected areas, such as oral mucosa,vulva, and penis have been described. The tumor spreads frequently; common secondary sites include the skin (28%), lymph nodes (27%), liver (13%), lung (10%), bones (10%), and brain (6%).Symptoms are typically local and related to tumor growth or lymph node involvement. Superior vena cava syndrome secondary to obstruction by tumor mass as well as paraneoplastic neurologic complications have been reported.

Most patients with MCC present with localized disease (70% to 80%); 10% to 30% of patients have regional lymph node involvement, and 1% to 4% have distant metastases at the time of initial presentation There is no accepted staging system for MCC, but several investigators have adopted a simple system proposed by Yiengpruksawan et al:stage I, localized skin disease (stage IA  2 cm, IB > 2 cm); stage II, regional lymph node disease; and stage III, metastatic disease. Purported favorable prognostic factors include primary tumor location in the head and neck region and without involvement of regional lymph nodes, tumors  2 cm in size (stage IA), and female sex.

Initially, MCC was thought to be a cancer with a good prognosis, as only one out of the first five patients described by Tokersuccumbed to the disease, and only three deaths occurred in the first 24 reported cases. However, MCC has subsequently been shown to be a highly aggressive and lethal tumor, comparable with small-cell lung cancer and melanoma in its behavior with regards to recurrence, metastatic spread, and mortality. The overall recurrence rate ranges from 55% to 79%, occurring most often locally or in regional lymph nodes, with the majority of recurrences appearing within the first 6 to 12 months after initial diagnosis.