Melanoma may be the most aggressive type of skin cancer, but it is not the most common. Basal cell carcinoma and squamous cell carcinoma are the most frequently occurring types.
Different types of skin cancers originate from specific cells in the epidermis. For example, melanoma develops from melanocytes, the cells responsible for producing melanin, that is the pigment that gives color to the skin and protects it from sunlight. W
Basal Cell Carcinoma
Basal cell carcinomas, sometimes informally referred to as basaliomas, consist of cells that resemble those in the basal layer of the epidermis. It is not only the most common skin cancer but also the most common cancer overall.
It receives less attention because it rarely metastasizes (spreads to other body parts). This carcinoma typically appears after the age of 50. Still, its occurrence is becoming increasingly common in younger age groups due to sun exposure.
Basal cell carcinomas often develop on the face (especially the nose), neck, and trunk—areas most exposed to sunlight.
Risk factors for basal cell carcinoma include:
- Phenotypic factors: fair skin, light-colored eyes, and hair, which increase the risk.
- Environmental risk factors: prolonged unprotected exposure to ultraviolet (UV) radiation. It’s important to note that UV radiation from tanning lamps and beds also harms the skin.
- UV radiation causing DNA mutations in epidermal cells: Tumors can develop when these mutations occur in genes critical for controlling cell growth. Therefore, individuals with basal cell carcinoma risk developing additional basaliomas or skin cancer caused by UV exposure.
- Gorlin-Goltz syndrome: a rare genetic predisposition. Individuals with this syndrome may develop basal cell carcinomas as early as 20 to 25 years of age, along with skeletal malformations, brain tumors, and depressions on the palms of the hands and soles of the feet.
Treatment of Basal Cell Carcinoma:
Basal cell carcinoma is a slow-growing tumor that rarely spreads to other organs. It has a favorable prognosis, and surgical removal is typically the chosen treatment.
Non-surgical therapies, such as imiquimod 5% cream (which activates the immune system) or photodynamic treatment (using aminolevulinate to sensitize cells to light), may be considered for superficial basal cell carcinomas.
In cases of locally advanced basal cell carcinoma where surgery is not feasible, radiation therapy or systemic therapy with hedgehog inhibitors may be used.
Squamous Cell Carcinoma
Squamous cell carcinoma can also originate from keratinocytes undergoing abnormal growth. This tumor has a more variable clinical course, ranging from noninvasive forms to those with the potential to spread.
Like basal cell carcinoma, squamous cell carcinoma develops primarily in sun-exposed areas of the skin. However, UV rays are not the sole cause; this tumor can originate in any area of the skin surface or mucous membranes.
Risk factors for squamous cell carcinoma include:
– Light phototype: Individuals with blond or red hair, fair skin, and blue or green eyes are at higher risk.
– UV exposure: Prolonged exposure to UV radiation, including using tanning beds and lamps, increases the risk.
– Immunosuppressive therapies: Squamous cell carcinoma is the most common type of cancer in transplant patients undergoing immunosuppressive treatment.
– Infection with papillomavirus (HPV): In some cases, HPV infection can facilitate the development of squamous cell carcinomas.
– Chronic skin ulcers: Although rare, long-lasting skin ulcers can promote the development of squamous cell carcinoma at the affected site.
– Genetic predisposing factors: These rare conditions include oculocutaneous albinism, xeroderma pigmentosum, and dystrophic epidermolysis bullosa.
Treatment of Squamous Cell Carcinoma:
Surgery is the primary treatment option for this tumor. However, in situ forms (such as Bowen’s disease) that have not yet invaded deeper layers of the skin may benefit from photodynamic therapy.
Radiotherapy and systemic drug therapies (such as cemiplimab) are available for locally advanced or metastatic forms of cutaneous squamous cell carcinoma. These therapies “activate” the immune system, specifically targeting cancer cells.
Actinic keratoses are superficial, noninvasive precancerous lesions caused by exposure to UV radiation. Identifying actinic keratoses is crucial, as they can develop into invasive squamous cell carcinomas if left untreated.
Characteristics of actinic keratoses:
– Small, rough pink or red patches that may merge.
– Commonly found on the face, back of the hands, and scalp of bald individuals. When found on the lower lip, they are called actinic cheilitis.
Treatment of Actinic Keratoses:
Isolated lesions can be treated with cryotherapy, curettage, or diathermocoagulation.
Extensive or confluent lesions may require photodynamic therapy or topical therapies, such as diclofenac, imiquimod, or 5-fluorouracil. These locally applied drugs work in different ways to target the “field of cancerization,” the area of skin exposed to UV radiation that changes not always visible to the naked eye. If left untreated, these changes increase the risk of developing squamous cell carcinoma.