What is skin cancer?
There are several types of skin cancer, including basal cell carcinoma, squamous cell carcinoma, melanoma (malignant melanoma), cutaneous lymphomas, and other rarer types.
In this overview, we focus on the most common types, collectively called keratinocyte carcinoma. Previously, these were referred to as nonmelanoma skin cancer. This group includes the precancerous lesions actinic keratosis and Bowen’s disease, as well as squamous cell carcinoma and basal cell carcinoma.
Remember: Although these types of skin cancer generally have an excellent prognosis, early detection is essential to reduce scarring and tissue loss. See a doctor if you notice new spots, growths, or sores that do not heal. Early diagnosis can make an important difference.
Actinic keratosis
Other terms: solar keratosis, precancerous sun damage
Actinic keratosis is a precancerous skin lesion that, in some cases, can develop into squamous cell carcinoma.
In brief:
- Caused by many years of exposure to ultraviolet (UV) radiation from the sun
- Appears as rough, red, thickened, or scaly patches on skin that has been exposed to the sun - typically on the face, scalp, chest, or arms
- Occurs most often in older adults with fair skin
- May cause itching or irritation and can be cosmetically bothersome
Is it dangerous?
Most actinic keratoses are not dangerous, but some can develop into squamous cell carcinoma over time, especially those on the lips. The risk of a single lesion progressing to skin cancer is low, but the total risk increases with the number of lesions present. Even when they do not progress, actinic keratoses are considered a warning sign of chronic sun damage and an increased risk of skin cancer.
Bowen’s disease
Other terms: squamous cell carcinoma in situ
Bowen’s disease is considered a precancerous condition or an early form of squamous cell carcinoma, in which cancer cells are confined to the superficial layer of the skin (the epidermis) and have not yet grown into deeper tissue.
In brief:
- Considered a precursor to invasive squamous cell carcinoma
- Mostly caused by long-term sun exposure but may also be associated with human papillomavirus (HPV), especially in the genital area
- Most commonly appears on the lower legs, arms, and torso, but can also occur on the genitals, around the nails or on mucous membranes
- Appears as a red, flat, slightly scaly patch that grows slowly
May resemble other skin conditions such as eczema or psoriasis or a sore that does not heal
Is it dangerous?
Bowen’s disease itself is not invasive cancer, but without treatment it can develop into invasive squamous cell carcinoma. The prognosis is excellent when detected and treated early.
Squamous cell carcinoma
Other terms: cutaneous squamous cell carcinoma, SCC
Squamous cell carcinoma typically grows faster than basal cell carcinoma and, in some cases, can spread (metastasize) to lymph nodes or internal organs.
In brief:
- Develops on sun-damaged skin, especially in older adults. Common locations include the face, scalp, ears, lips, and backs of the hands.
- Risk increases with fair skin, weakened immune system, and long-term UV exposure.
- May develop from precancerous lesions such as actinic keratosis or Bowen’s disease.
- Often appears as a firm growth that may become crusted, ulcerated, or bleed. Some people experience tenderness, swelling, or pain in the affected area.
Is it dangerous?
Squamous cell carcinoma is the second most common type of skin cancer and can be serious, especially when located on the lips, ears, or mucous membranes. In approximately 1.2-5% of cases, it spreads to other parts of the body. However, most patients are completely cured when the cancer is detected and treated early.
Basal cell carcinoma
Other terms: basal cell skin cancer, BCC
Basal cell carcinoma is the most common type of skin cancer.
In brief:
- Grows slowly and rarely spreads (metastasizes), but can grow into surrounding tissue and cause local damage if not treated early.
- Most often develops on sun-exposed areas such as the face, head, and upper body, especially in people with fair skin and significant sun exposure.
- May appear as a sore that does not heal, a reddish patch, a shiny bump, or a growth that may crust or bleed.
Is it dangerous?
Basal cell carcinoma is rarely life-threatening, but it can be locally destructive if left untreated. It almost never spreads to other parts of the body, and death from basal cell carcinoma is extremely rare. However, larger or deeper tumors can cause scarring, disfigurement, or tissue loss, particularly when located on the face.