Basal cell carcinoma (BCC) is the most common malignancy afflicting mankind. Sometimes referred to as a rodent ulcer, the tumor was recognized by the Egyptians, Greeks, and Romans in ancient times.1 In 1827, Arthur Jacob provided the first detailed clinical definition of BCC in a publication titled "Observations respecting an ulcer of peculiar character, which attacks the eye-lids and other parts of the face."2
Basal cell carcinoma usually occurs in fair-skinned individuals with sun-damaged skin.3 It is three to four times more common than squamous cell carcinoma (SCC) and its incidence varies dramatically across various regions of the world reflecting the ethnic mix, ambient ultraviolet (UV) light exposure, and sun behavior habits of the population.3 The highest rates of BCC occur in Australia where national studies have documented a rate of 884/100,000 person-years, with an even higher incidence rate in some regions.3,4 The lowest recorded rates of BCC are in parts of Africa, with rates of less than 1/100,000 person-years.3 Globally, the incidence of BCC is increasing and European studies indicate that rates of BCC in Europe have been increasing on average by 5.5% each year.3 This increase in incidence is particularly dramatic in older age groups, with the greatest increase occurring in people aged 60 years and older.5 Less than 1% of all BCCs occur in individuals less than 25 years of age and there is a gender disparity in incidence with males affected more commonly than females; however, the extent of the disparity varies depending on the subtype of BCC.6 Anatomically, BCCs are most commonly identified on the face, followed by the neck, shoulders, back, and upper limbs.7 The relative density of BCCs is low in body sites that receive little sun exposure, namely the buttocks, thighs, feet, and in women, the scalp.7
BCCs rarely metastasize, with only approximately 300 to 400 cases reported in the literature.8,9 The rate of metastasis is reported to be between 0.0028% and 0.55%, but it is likely to be closer to 0.0028%, as noted in a survey of Australian dermatologists.8,9 A number of tumor characteristics have been identified that are associated with an increased risk of developing metastases. These include male gender, lesions on the head and neck, lesion size (with larger and locally invasive (T4) lesions being at higher risk), and recurrence after surgery or radiotherapy.9,10 The most common site for metastatic spread is to regional lymph nodes; however, hematogenous spread occurs very occasionally, with involvement of lung, bone, and to a lesser extent other internal organs.10
As well as skin phototype, risk factors for the development of BCC include cumulative and sun-burning UV radiation, immunosuppression, genetic disorders, HIV/AIDS, ionizing radiation, photosensitizing medications, and arsenic and occupational ...