Sunlight, particularly long-term exposure, is the most frequent association with development of BCC; risk correlates with the amount and nature of accumulated exposure, especially during childhood. Patient geographic location affects the risk of developing skin cancer. A latency period of 20-50 years is typical between the time of ultraviolet (UV) damage and BCC clinical onset.
The prevalence of BCC increases in areas of higher altitude and in areas of lower latitude. The incidence of BCC is rising, potentially because of atmospheric changes and the increased popularity of sunbathing.
Radiation exposure that contributes to BCC development may also include tanning booths and UV light therapy. Both short-wavelength UVB radiation (290-320 nm, sunburn rays) and longer wavelength UVA radiation (320-400 nm, tanning rays) contribute to the formation of BCC. UVB is believed to play a greater role in the development of BCC than UVA, however, and is the primary agent responsible for most skin cancer. [31]
UVB and UVC can modify unsaturated chemical bonds of nucleic acids, which may lead to mutations. UVC does not penetrate the atmospheric ozone layer. The UVA spectrum is absorbed by melanin and, through free-radical transfer, affects cellular deoxyribonucleic acid (DNA). Mutations caused by UV radiation typically include cytosine (C) to thymine (T), or CC to TT, translocation. This process can cause activation of oncogenes or inactivation of tumor suppressor genes, leading to tumor initiation and progression. [32]
The skin can repair superficial damage, but the underlying cumulative damage remains, including DNA damage. The damage worsens with each successive sun exposure, causing a lifetime progression. [33]
In a 2012 systematic review and meta-analysis of 12 studies with 9328 cases of non-melanoma skin cancer, Wehner et al found that indoor tanning was associated with a significantly increased risk of both basal and squamous cell skin cancer. The risk was highest among users of indoor tanning before age 25. The authors estimate that the population attributable risk fraction in the United States is 8.2% for squamous cell carcinoma and 3.7% for basal cell carcinoma, corresponding to more than 170,000 cases of non-melanoma skin cancer annually caused by indoor tanning. [34] In another 2012 study of 376 patients with basal cell carcinoma and 390 control patients with minor benign skin conditions, indoor tanning was strongly associated with early-onset basal cell carcinoma, particularly in women. [35]
X-ray and Grenz-ray exposure are also associated with basal cell carcinoma formation.
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A pink, scaly lesion on the skin. Superficial basal cell carcinoma (BCC) is often misdiagnosed as eczematous dermatitis or guttate psoriasis and is often difficult to distinguish clinically from Bowen disease (squamous cell carcinoma in situ). Features that suggest the diagnosis of superficial BCC are the absence of significant white, adherent scale and a history of the lesion remaining unchanged for several months or years. Treatment options for this tumor include electrodesiccation and curettage, surgical excision, cryosurgery, 5-fluorouracil, 5% imiquimod cream, and superficial radiotherapy. Electrodesiccation and curettage is the modality most commonly used, with a cure rate of approximately 95%.
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Basal cell carcinoma.
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A 68-year-old patient presenting with an advanced basal cell carcinoma (BCC) of the right periorbital region, frontal view. Courtesy of M Abraham Kuriakose, DDS, MD.
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Lateral view of face showing extent of tumor. Courtesy of M Abraham Kuriakose, DDS, MD.
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Basal cell carcinoma of the right lower lid.
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Biopsy-proven basal cell carcinoma of the upper lid margin. Note the loss of cilia (madarosis) in the area of the tumor.
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Medial canthal/lower lid basal cell. Note the pearly nodular surface with characteristic telangiectatic vessels. Proximity to the lacrimal system will impact its treatment and reconstruction.
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Nodular basal cell carcinoma.
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Nodular basal cell carcinoma appearing as a waxy, translucent papule with central depression and a few small erosions.
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Scale, erythema, and a threadlike raised border are present in this superficial basal cell carcinoma on the trunk.
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Large, superficial basal cell carcinoma.
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Basal cell carcinoma. Courtesy of Hon Pak, MD.
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Pigmented basal cell carcinoma.
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Pigmented basal cell carcinoma.
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Pigmented basal cell carcinoma has features of nodular basal cell carcinoma with the addition of dark pigmentation from melanin deposition. The pigmentation often has the appearance of dark droplets in the lesion, as shown here.
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This infiltrating basal cell cancer has ill-defined borders and telangiectases.
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This translucent pink papule has telangiectases and a crusted erosion, characteristic of nodular basal cell carcinoma.
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Large, scarlike morpheaform basal cell cancer.
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Nodular basal cell carcinoma. Nodular aggregates of basalioma cells are present in the dermis and exhibit peripheral palisading and retraction artifact. Melanin is also present within the tumor and in the surrounding stroma, as seen in pigmented basal cell carcinoma.
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Histologic pattern of a well-differentiated basal cell carcinoma (original magnification X140). Courtesy of Prof Pantaleo Bufo, University of Foggia, Italy.
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Histologic pattern of a well-differentiated basal cell carcinoma (original magnification X250). Courtesy of Prof Pantaleo Bufo, University of Foggia, Italy.
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Micronodular basal cell carcinoma often has an absence of retraction artifact. The characteristic histology is small size and uniformity of the tumor nodules. Courtesy of Shang I Brian Jiang, MD.
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Infiltrative basal cell carcinoma. Tumor cells are arranged in narrow strands, and mucin-rich stroma is often present. Courtesy of Shang I Brian Jiang, MD.
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Keratotic basal cell carcinoma. Rare type characterized by keratocysts. Courtesy of Shang I Brian Jiang, MD.
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Basosquamous basal cell carcinoma. Foci of neoplastic cells with squamous differentiation are present. Courtesy of Shang I Brian Jiang, MD.
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Histology of superficial basal cell carcinoma. Nests of basaloid cells are seen budding from the undersurface of the epidermis. Courtesy of Michael L Ramsey, MD.
