An overview of where nonmelanoma cancers appear in the hierarchy of cancers is succinctly presented, as well as their incidence, etiology, and costs. The examination and treatment of these cancers are summarized.
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Skin cancers, mainly classified as melanoma and nonmelanoma skin cancers (NMSCs), are the most common cancers in humans.
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The most common types of NMSCs are basal cell carcinoma and squamous cell carcinoma.
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Nonmelanoma skin cancers are generally considered as a neglected health problem owing to their low morbidity and mortality; however, the economic burden of health interventions in NMSC is on the increase.
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Patients with a NMSC are generally complained of a nonhealing, ulcerative, and bleeding lesion.
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A dermoscopic examination of a suspicious lesion is helpful for differential diagnosis; and excision or biopsy is generally recommended for histopathological evaluation.
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The gold standard treatment modality for NMSCs is surgical resection.
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Surgical margin control has a paramount importance for decreasing the rate of tumor recurrence.
Skin cancer incidence
Skin cancers are the most common cancers in humans, especially in the white population. They are mainly classified as melanoma and nonmelanoma skin cancers (NMSCs). Unfortunately, the worldwide incidence of NMSCs is not known exactly; they are generally considered a neglected health problem owing to their low morbidity and mortality. Therefore, the cancer registration databases are unreliable even in most of the developed countries; however, evidence demonstrates that the incidence of NMSC has continually and dramatically increased over the past decades in the western world. A recent systematic review that evaluated the global incidence for NMSCs determined that Australia has the highest incidence in the world. In 2002, the reported incidence for NMSCs in Australia was 1170/100,000 and the estimated number of patients with NMSCs was 374,000. In addition, the economic burden spent on the care settings and treatment modalities of NMSCs was more than $264 million. Meanwhile, the incidence for NMSCs in the United States cannot be regarded as too low to overlook. In the United States, the estimated total number of new NMSCs was 3,507,693 in 2006, and approximately 3.69 million in 2008. The estimated total cost of NMSCs was approximately $426 million per year in the Medicare population. In addition, Guy and Ekwueme reported the years of potential life lost and indirect expenditures of skin cancers (including melanoma and NMSCs), which ranged from $28.9 to $39.2 million for morbidity, and $1.0 to $3.3 billion for mortality. Epidemiologic studies and health economic analysis highlight that the incidence of NMSCs is increasing and it is becoming an important public health problem worldwide with an increasing economic impact. Therefore, several countries and the World Health Organization (INTERSUN program) recommend and encourage preventive strategies (eg, sun-protective behaviors and attitudes, topical sunscreens) against skin cancers. In addition, skin cancer screening programs have been implemented recently with promising results in certain countries, such as Germany.
Common types of nonmelanoma skin cancers
The most common types of NMSCs are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), although several other rare types, such as Merkel cell carcinoma and sebaceous gland carcinoma are also present.
The major etiologic factor for the development of NMSCs is overexposure to solar ultraviolet (UV) radiation, especially UVB (ranging 320 to 290 nm). Therefore, the sun-exposed skin regions, such as the head, neck, and extremities, are at higher risk for the development of NMSCs. The development of BCC is associated with intermittent exposure to the sun. The development of actinic keratosis (precancerous progenitor of SCC) and/or invasive SCC is associated with continual, chronic sun exposure . UV radiation-induced carcinogenesis in NMSCs is basically related to a defect in the repair of UV radiation-induced DNA damage. In BCC, mutations in Hedgehog signaling pathway–related genes, and in SCC, mutations in p53 tumor suppressor genes play a key role.
Basal Cell Carcinoma
Basal cell carcinoma, the most frequent subtype of NMSCs, originates from the basal cells of the epidermis. It almost always invades the local structures; however, it rarely metastasizes. It has various subtypes, which are mainly classified according to their clinical and histopathological characteristics: noduloulcerative, superficial, morpheaform, infiltrative, basosquamous, cystic, and fibroepithelioma of Pinkus. Noduloulcerative and superficial BCC are the most common subtypes and generally involve the head and neck regions. Morpheaform, infiltrative, and basosquamous subtypes of BCC are less commonly detected; however, they have a more aggressive behavior.
Squamous Cell Carcinoma
Squamous cell carcinoma originates from epidermal keratinocytes. It is a locally aggressive skin cancer, which also has the potential to metastasize to regional lymph nodes and distant structures. The incidence of regional lymph node involvement in cutaneous SCC of the head and neck is approximately 5%; and the lymph nodes in the parotid gland are a metastatic basin for cutaneous SCC of the head and neck. Unfortunately, the survival of patients with metastatic cutaneous SCC decreases dramatically (overall 5-year survival rate of 34.4%).
Common types of nonmelanoma skin cancers
The most common types of NMSCs are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), although several other rare types, such as Merkel cell carcinoma and sebaceous gland carcinoma are also present.
The major etiologic factor for the development of NMSCs is overexposure to solar ultraviolet (UV) radiation, especially UVB (ranging 320 to 290 nm). Therefore, the sun-exposed skin regions, such as the head, neck, and extremities, are at higher risk for the development of NMSCs. The development of BCC is associated with intermittent exposure to the sun. The development of actinic keratosis (precancerous progenitor of SCC) and/or invasive SCC is associated with continual, chronic sun exposure . UV radiation-induced carcinogenesis in NMSCs is basically related to a defect in the repair of UV radiation-induced DNA damage. In BCC, mutations in Hedgehog signaling pathway–related genes, and in SCC, mutations in p53 tumor suppressor genes play a key role.
Basal Cell Carcinoma
Basal cell carcinoma, the most frequent subtype of NMSCs, originates from the basal cells of the epidermis. It almost always invades the local structures; however, it rarely metastasizes. It has various subtypes, which are mainly classified according to their clinical and histopathological characteristics: noduloulcerative, superficial, morpheaform, infiltrative, basosquamous, cystic, and fibroepithelioma of Pinkus. Noduloulcerative and superficial BCC are the most common subtypes and generally involve the head and neck regions. Morpheaform, infiltrative, and basosquamous subtypes of BCC are less commonly detected; however, they have a more aggressive behavior.
Squamous Cell Carcinoma
Squamous cell carcinoma originates from epidermal keratinocytes. It is a locally aggressive skin cancer, which also has the potential to metastasize to regional lymph nodes and distant structures. The incidence of regional lymph node involvement in cutaneous SCC of the head and neck is approximately 5%; and the lymph nodes in the parotid gland are a metastatic basin for cutaneous SCC of the head and neck. Unfortunately, the survival of patients with metastatic cutaneous SCC decreases dramatically (overall 5-year survival rate of 34.4%).
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