Basal cell carcinoma (BCC) is the most common type of skin cancer, accounting for approximately 80-85% of all skin cancers. It is a type of non-melanoma skin cancer that originates in the basal cell layer of the skin.

**Causes and Risk Factors:**

1. **Ultraviolet (UV) radiation**: Exposure to UV radiation from the sun or tanning beds is the primary cause of BCC.
2. **Fair skin**: People with fair skin, light hair, and light eyes are more susceptible to BCC.
3. **Age**: BCC is more common in people over 50 years old.
4. **Genetics**: Family history and genetic predisposition can increase the risk of developing BCC.
5. **Previous skin cancer**: People who have had previous skin cancers, including BCC, are at increased risk of developing another BCC.

**Symptoms:**

1. **Appearance**: BCC typically appears as a small, shiny, pink or red bump on the skin.
2. **Location**: BCC often occurs on sun-exposed areas, such as the face, ears, neck, and hands.
3. **Size**: BCC can range in size from a few millimeters to several centimeters in diameter.
4. **Bleeding**: BCC may bleed easily, especially when injured.

**Types of Basal Cell Carcinoma:**

1. **Nodular BCC**: The most common type, characterized by a small, shiny bump.
2. **Superficial BCC**: A flat, reddish-pink patch on the skin.
3. **Sclerosing BCC**: A firm, waxy lesion that can be difficult to distinguish from a scar.
4. **Pigmented BCC**: A BCC with melanin, which can resemble a melanoma.

**Diagnosis:**

1. **Visual examination**: A dermatologist will examine the skin lesion visually.
2. **Biopsy**: A skin biopsy may be performed to confirm the diagnosis.

**Treatment:**

1. **Surgical excision**: The most common treatment, where the tumor is surgically removed.
2. **Mohs surgery**: A specialized surgical technique that removes the tumor layer by layer.
3. **Cryotherapy**: Freezing the tumor with liquid nitrogen.
4. **Topical treatments**: Applying creams or gels that contain medications, such as imiquimod or fluorouracil.
5. **Radiation therapy**: May be used in some cases, especially if the tumor is large or in a sensitive area.

**Prevention:**

1. **Sun protection**: Use sunscreen with at least SPF 30, wear protective clothing, and seek shade.
2. **Avoid tanning beds**: Tanning beds emit UV radiation, which increases the risk of BCC.
3. **Regular skin checks**: Perform regular self-examinations and consult a dermatologist if you notice any suspicious skin lesions.

**Prognosis:**

Basal cell carcinoma is generally a treatable and curable form of skin cancer. If left untreated, BCC can cause local destruction of tissue and potentially lead to disfigurement. However, it is rare for BCC to metastasize (spread) to other parts of the body.