Basal-Cell Carcinoma

Basal-cell carcinoma (BCC), also known as basal-cell cancer, basalioma, or rodent ulcer, is the most common type of skin cancer. It often presents as a painless raised area of skin, which may be shiny with small blood vessels running over it or may present as an ulcerated area.

Unlike other skin cancers, BCC grows slowly and typically does not spread to distant parts of the body or result in death.

Signs and Symptoms

Individuals with BCC often present with a shiny, pearly skin nodule. Superficial BCC can appear as a red patch similar to eczema, while infiltrative or morpheaform BCCs might look like skin thickening or scar tissue, making diagnosis difficult without tactile sensation and a skin biopsy.

Cause

The majority of BCCs occur on sun-exposed areas of the body. Overexposure to ultraviolet (UV) light leads to DNA damage, which may not be fully repaired, leading to mutations. UV exposure during childhood is particularly harmful and tanning beds are a common source of UV radiation. Other risk factors include having lighter skin, previous radiation therapy, long-term exposure to arsenic, and poor immune function.

Pathophysiology

BCC is named after the basal cells that form the lowest layer of the epidermis, although it is thought to develop from folliculo–sebaceous–apocrine germinative cells known as trichoblasts. Overexposure to sunlight leads to the formation of thymine dimers, a form of DNA damage that may lead to mutations if not repaired.

Diagnosis

Diagnosis is typically made through skin examination and confirmed by a skin biopsy. A shave biopsy under local anaesthesia is the most common method. Nodular BCCs can often be diagnosed clinically, while other variants may require immunohistochemistry using markers like BerEP4 for confirmation.

Treatment

Standard Surgical Excision

Surgery to remove the affected area along with the surrounding skin is considered the most effective treatment. However, recurrence rates can be higher for facial BCCs.

Mohs Surgery

Mohs surgery involves the excision of the tumour followed by immediate microscopic examination of the margins. This process is repeated until no cancer cells are detected, making it highly effective for recurrent and facial BCCs.

Cryosurgery

Cryosurgery involves freezing the tumour with liquid nitrogen, but it lacks the margin control of other methods and may lead to tissue necrosis.

Electrodesiccation and Curettage (EDC)

This method involves scraping away the cancer with a curette followed by burning the area with an electric current. It's often used for tumours on cosmetically unimportant areas like the trunk.

Chemotherapy

Topical chemotherapeutic agents such as 5-fluorouracil are used for superficial BCCs. New drugs like vismodegib and sonidegib are used for advanced cases but are expensive and have specific contraindications.

Immunotherapy

Topical treatments like 5% Imiquimod cream have shown success rates in reducing or removing BCCs. Imiquimod is FDA-approved and can be used before surgery to reduce tumour size.

Radiation

Radiation therapy is generally reserved for older patients or cases where surgical excision would be disfiguring. It is also used post-surgery if high recurrence risk is indicated.

Photodynamic Therapy (PDT)

PDT uses photosensitizers that become toxic when activated by light to destroy cancer cells. It is effective for primary superficial and low-risk nodular BCCs.

Prognosis

Prognosis is generally excellent if BCC is treated early. Recurrent cancers are more challenging to cure. Although BCC rarely metastasizes, it can grow locally, invading and destroying adjacent tissues.

Epidemiology

BCC is particularly common in fair-skinned individuals and those with a family history of the disease. Sun exposure and age are significant risk factors. In the UK and other regions, BCC accounts for a large proportion of non-melanoma skin cancers, with higher incidences in elderly populations.

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Self-assessment MCQs (single best answer)

What is the most common type of skin cancer?

Which of the following is NOT a common presentation of basal-cell carcinoma?

What is the primary cause of basal-cell carcinoma?

Which surgical procedure involves the excision of the tumour followed by immediate microscopic examination of the margins?

Which topical treatment is FDA-approved for reducing or removing basal-cell carcinomas?

Basal-cell carcinoma is thought to develop from which type of cells?

What is a common risk factor for developing basal-cell carcinoma?

Which diagnostic marker is often used in immunohistochemistry for confirming BCC?

What is the most common method of biopsy for diagnosing basal-cell carcinoma?

Which treatment method uses photosensitizers activated by light to destroy cancer cells?