(See also Overview of Skin Cancer.)
Basal cell carcinoma is the most common type of skin cancer, with > 4 million new cases yearly in the United States. It is most common among fair-skinned people with a history of sun exposure and is very rare in darkly pigmented people.
Basal cell carcinomas are also associated with genetic syndromes and may arise in a nevus sebaceous. Xeroderma pigmentosum represents an inherited defect in DNA repair that can result in nonmelanoma skin cancer and in melanoma. Basal cell nevus syndrome (Gorlin syndrome) is an autosomal dominant disorder that results in multiple basal cell carcinomas as well as in medulloblastomas, meningiomas, breast cancers, non-Hodgkin lymphomas, and ovarian cancers. Bazex syndrome is a rare genodermatosis that can result in the early onset of multiple basal cell carcinomas.
The clinical manifestations and biologic behavior of basal cell carcinomas are highly variable. The most common types are
Nodular (about 60% of basal cell carcinomas): These types are small, shiny, firm, almost translucent to pink nodules with telangiectases, usually on the face. Ulceration and crusting are common.
Superficial (about 30%): These types are red or pink, marginated, thin papules or plaques, commonly on the trunk, that are difficult to differentiate from psoriasis or localized dermatitis.
Morpheaform (5 to 10%): These types are flat, scarlike, indurated plaques that can be flesh-colored or light red and have vague borders.
Other: Other types are possible. Nodular and superficial basal cell carcinomas can produce pigment (sometimes called pigmented basal cell carcinomas).
Most commonly, the carcinoma begins as a shiny papule, enlarges slowly, and, after a few months or years, shows a shiny, pearly border with prominent engorged vessels (telangiectases) on the surface and a central dell or ulcer. Recurrent crusting or bleeding is not unusual. Commonly, the carcinomas may alternately crust and heal, which may unjustifiably decrease patients' and physicians' concern about the importance of the lesion.
Basal cell carcinomas rarely metastasize but may invade healthy tissues. Rarely, patients die because the carcinoma invades or impinges on underlying vital structures or orifices (eg, eyes, ears, mouth, bone, dura mater).
Almost 25% of patients with a history of basal cell carcinoma develop a new basal cell cancer within 5 years of the original carcinoma. Consequently, patients with a history of basal cell carcinoma should be seen annually for a skin examination.
Treatment of basal cell carcinoma should be done by a specialist.
The clinical appearance, size, site, and histologic subtype determine choice of treatment—curettage and electrodesiccation, surgical excision, cryosurgery, topical chemotherapy (imiquimod or 5-fluorouracil) and photodynamic therapy, or, occasionally, radiation therapy.
Recurrent or incompletely treated cancers, large cancers, cancers at recurrence-prone sites (eg, head and neck), and morphea-like cancers with vague borders are often treated with Mohs microscopically controlled surgery, in which tissue borders are progressively excised until specimens are tumor-free (as determined by microscopic examination during surgery).
If patients have metastatic or locally advanced disease and are not candidates for surgery or radiation therapy (eg, because lesions are large, recurrent, or metastatic), vismodegib and sonidegib may be given. Both drugs inhibit the hedgehog pathway (a pathway that affects response to radiation therapy and chemotherapy in some tumors and is abnormally mutated in most patients with basal cell carcinoma).
Because basal cell carcinoma seems to be related to ultraviolet (UV) exposure, a number of measures are recommended to limit exposure.
Sun avoidance: Seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when sun's rays are strongest), and avoiding sunbathing and the use of tanning beds
Use of protective clothing: Long-sleeved shirts, pants, and broad-brimmed hats
Use of sunscreen: At least sun protection factor (SPF) 30 with broad-spectrum UVA/UVB protection, used as directed (ie, reapplied every 2 hours and after swimming or sweating); should not be used to prolong sun exposure
Basal cell carcinomas, the most common skin cancers, are particularly common among fair-skinned people on sun-exposed skin.
Consider the diagnosis with typical lesions (eg, shiny, slowly enlarging papule, often with a shiny, pearly border) and lesions that alternately crust and heal.
Refer patients to specialists for treatment, usually by locally destructive methods.