Basal cell carcinoma (BCC) is the most frequently diagnosed form of skin cancer, originating within the skin’s basal cells. This cancer typically grows slowly and rarely spreads to distant body parts. While it seldom metastasizes, early detection and treatment are important to prevent localized tissue damage.
Where Basal Cell Cancer Begins
Basal cell carcinoma begins in basal cells, specialized cells located in the deepest layer of the epidermis, the skin’s outermost layer. These cells continuously produce new skin cells to replace older ones that are shed from the surface. As new cells form, they push older cells upward, where they eventually die and are sloughed off.
BCC arises when DNA within these basal cells incurs damage. This damage disrupts their normal regulatory processes, leading to uncontrolled cellular growth. BCC typically arises from the basal layer of the interfollicular epidermis, the part of the epidermis between hair follicles.
Key Contributing Factors
Ultraviolet (UV) radiation is a primary factor contributing to BCC development. Both chronic and intense exposure to UV rays, from natural sunlight or artificial sources like tanning beds, can damage skin cells. While both UVA and UVB rays contribute, short-wavelength UVB radiation, known for causing sunburn, plays a greater role in BCC formation.
Genetic predisposition also influences risk, particularly for individuals with fair skin, light hair, and blue or green eyes who tend to sunburn easily. These individuals have lower levels of melanin, which provides natural protection against UV radiation. Rare inherited syndromes, such as Gorlin syndrome, increase the likelihood of developing multiple BCCs, often at an earlier age.
Age is another factor, as BCC risk increases with cumulative UV exposure over a lifetime, often manifesting in older adults. However, BCC incidence is also rising in younger individuals, particularly those in their 20s and 30s, likely due to increased recreational sun exposure and tanning bed use. A history of previous skin cancers, including BCC itself, elevates the risk of developing new lesions.
A weakened immune system, often due to medications after organ transplant surgery or certain medical conditions, can increase susceptibility. Immunosuppression reduces the body’s ability to repair UV-damaged skin cells, raising the risk. Exposure to certain environmental toxins, such as arsenic, can also contribute to BCC formation.
The Cellular Development Process
BCC begins with DNA damage within basal cells, most often induced by UV radiation. This radiation can directly alter DNA structure or generate reactive oxygen species that cause secondary damage. Cells typically have repair mechanisms, but if the damage is too extensive or repair is faulty, these alterations become permanent.
Unrepaired DNA damages can lead to mutations in critical genes that regulate cell growth and division. For instance, mutations in genes of the Hedgehog signaling pathway, such as PTCH1 and SMO, are frequently observed in BCC. Mutations in tumor suppressor genes like TP53 also commonly occur, affecting the cell’s ability to control its growth.
As mutations accumulate, they disrupt the normal cell cycle, leading to uncontrolled proliferation of the damaged basal cells. These cells ignore the body’s natural signals to stop dividing, resulting in an abnormal accumulation of cells that form a tumor. This unchecked growth is a hallmark of cancer development.
Another aspect of this cellular malfunction is the failure of these damaged cells to undergo programmed cell death, known as apoptosis. Normally, cells with significant DNA damage are triggered to self-destruct, preventing them from becoming cancerous. In BCC, mutations can interfere with this protective mechanism, allowing defective cells to survive and multiply, contributing to tumor formation.
Recognizing Early Signs
Basal cell carcinoma often first appears as a new growth or a change in the skin on sun-exposed areas like the face, neck, ears, and hands.
One common presentation is a pearly or waxy bump that may appear translucent, sometimes with tiny visible blood vessels on its surface. This bump might be skin-colored, pink, or on darker skin tones, brown or glossy black.
Another sign can be a flat, flesh-colored or brown lesion that might resemble a scar. Some BCCs manifest as a bleeding or oozing sore that heals temporarily and then returns, indicating persistent skin damage. A reddish patch or an irritated area, particularly on the chest or back, could also signify an early BCC.
Other appearances include a shiny bump or nodule with a slightly raised, rolled edge and a central indentation. BCC can present in various ways and might sometimes be mistaken for non-cancerous skin conditions like eczema or psoriasis.