Basal cell carcinoma

Basal cell carcinoma (BCC) is the most common form of skin cancer. It can be destructive and disfiguring. The risk of developing BCC is increased for individuals with a family history of the disease and a high cumulative exposure to UV light via sunlight or, in the past, carcinogenic chemicals especially arsenic. Treatment is with surgery, topical chemotherapy, x-ray, cryosurgery, photodynamic therapy. It is rarely life-threatening but if left untreated can be disfiguring, cause bleeding and produce local destruction (eg., eye, ear, nose, lip).

Forms

Various forms are recognised:

    * Nodular: flesh-colored papule with telangiectasis. If it ulcerates, it becomes a "rodent ulcer" (ulcus rodens), an ulcerating nodule with (often) a pearly border.

    * Cystic: rarer and hard to distinguish from the nodular form. It has a central cavity with fluid.

    * Pigmented: a variant of the nodular form that may be confused with melanoma.

    * Sclerosing/cicratising: a scar-like lesion.

    * Superficial: a red scaling patch

About two-thirds of basal cell carcinomas occur on sun-exposed areas of the body. One-third occur on areas of the body that are not exposed to sunlight, emphasizing the genetic susceptibility of the basal cell cancer patients.

Presentation

Presents as a firm nodule, clearly growing within the skin and below it, rather than on the surface.

Color varies from that of normal skin to dark brown or black, but there is a characteristic "pearly white" translucent quality on the periphery.

Characteristic "rolled edge". Once the basal cells have invaded the deeper tissues the rolled edge disappears.

When BCCs occur at sites other than the face and neck they are usually just red, flat, scaling areas. Thus superficial BCCs can often be confused with a patch of eczema.

Diagnosis

To diagnose, a biopsy (where tissue is taken for pathological study) is done using local anesthesia. In small lesions, the tumor is generally removed in its entiriety, while larger ones are biopsied first and surgically removed later if it is confirmed that it is malignant.

Histopathology: Basal cell carcinoma is a malignant epithelial tumor arising only in skin, from the basal layer of the epidermis or of the pilosebaceous adnexa. Tumor is represented by compact areas, well delineated and invading the dermis, apparent with no connection with the epidermis. Tumor cells resemble normal basal cells (small, monomorphous) are disposed in palisade at the periphery of the tumor nests, but are spindle-shaped and irregular in the middle. Tumor clusters are separated by a reduced stroma with inflammatory infiltrate.

Pathophysiology

Basal cell carcinomas develop in the basal cell layer of the skin. Sunlight exposure leads to the formation of thymine dimers, a form of DNA damage. While DNA repair removes most UV-induced damage, not all crosslinks are excised. There is, therefore, cumulative DNA damage leading to mutations. Apart from the mutagenesis, sunlight depresses the local immune system, possibly decreasing immune surveillance for new tumor cells.

Prevention and Early Diagnosis

Basal cell carcinoma is the most common skin cancer. It occurs mainly in fair-skinned patients with a family history of this cancer. Sunlight is a factor in about two thirds of these cancers, but one third occur in non sun-exposed areas. Therefore, dermatologists recommend sun screens and annual skin cancer exams to prevent or provide early detection of this common tumor.

Treatment

Most basal cell carcinomas are removed surgically. A common method is "electrodessication and curettage" (ED&C). This is done by scraping the tumor out with a curette and cauterizing the base and margins. The wound is left to heal by itself (secondary intention healing). The cure rate and cosmetic result are excellent, especially in concave areas. It is also the most cost effective treatment. Surgical excision by the dermasurgeon is another option with the margins of excised tissue examined under the microscope. Certain types, like the sclerosing basal cell cancers may need a wider margin, as they develop subtle processes that project outside the visible part of the tumor. Although BCCs are termed carcinomas, they are not invasive cancers - and are therefore not included in national cancer statistics.

Some superficial cancers respond to local therapy with 5-fluorouracil, a chemotherapy agent. Topical treatment with 5% IMIQUIMOD cream (see below also), with 5 applications per week for six weeks has a reported 70 - 90% success rate at reducing, even removing the BCC [basal cell carcinoma]. Imiquimod may be used prior to surgery to reduce the size of the carcinoma. See Chemotherapy. One can expect a great deal of inflammation with this treatment.

Mohs micrographic surgery has the highest cure rate and is especially indicated for recurrent tumors or tumors in areas (eg. eyelid or nose) where minimal amounts of tissue removal are important. Mohs surgery involves checking the base and edges under a microscope before the surgical repair of the site. Specially trained dermasurgeons do this procedure, usually in-office.

A new immune enhancement agent (topical imiquimod, "Aldara") is effective for the treatment of superficial skin cancers (basal cell and squamous cell cancer, and even malignant melanoma in-situ). It is also used pre-operatively to shrink nodular basal cell cancers, thus allowing a smaller surgical excision.

X-ray is still appropriate in older patients who are not candidates for surgery. Cryosurgery is another option, particularly for basal cell cancer invading cartilage, as the healthy cartilage is cryo-resistant.

Treating surgeons (dermasurgeons, plastic surgeons, or other specialists) will recommend one of these modalities as appropriate treatment depending on the tumor size, location, patient age and other variables.

There is also a new treatment using Euphorbia peplus a common garden weed.

Prognosis