BCC is the most common skin cancer and, indeed, the most common malignancy in the United States and Australia. It outnumbers cutaneous squamous cell carcinoma by approximately four to one. Its origin lies in the basal layer of the epithelium or the external root sheath of the hair follicle. Classic teaching holds that BCC requires stromal participation for survival, not the malignant transformation of preexisting mature epithelial structures seen in SCC.
Although its metastatic potential is very low, basal cell carcinomas exhibit oncogene and tumor suppressor gene characteristics that question this classic explanation. Basal cell carcinoma tends to follow the path of least resistance, spreading into adjacent tissues. It only rarely metastasizes to distant sites.
Multiple histologic classifications have been proposed for subtypes of BCC, however, only the most common are mentioned here. Nodular BCC is the most common (45-60%), found typically as single translucent papules on the face. It is firm, may ulcerate, and often exhibits telangiectasia. Superficial BCC (15-35%) occurs as multiple scaly lesions on the trunk.
Lightly pigmented or erythematous, it may resemble psoriasis or eczema. The less common subtypes are usually more aggressive. These include infiltrative BCC (10-20%), morpheic BCC (9%), which is associated with the highest recurrence rate, micronodular BCC (15%) and adenoid BCC (precise incidence unknown).
Exposure to ultraviolet radiation appears to play a major role in the development of BCC. A thorough history during the preoperative evaluation should investigate this, making special mention of any significant sunburns during childhood or adolescence.
Other risk factors include exposure to radiation or chemical carcinogens such as arsenic, Fitzpatrick skin type 1 or 2 (fair skin), increasing age, male sex, xeroderma pigmentosum, albinism and immunosuppression. Patients with basal cell nevus syndrome may develop multiple basal cell carcinomas.
This syndrome, known eponymously as Goltz-Gorlin syndrome, is characterized by odontogenic keratocysts, palmar or plantar pits, cleft lip or palate, rib anomalies and areas of ectopic calcification. Nevus sebaceous lesions also predispose to BCC. As hairless yellow plaques present at birth, these lesions are typically found in the head and neck region. They may undergo malignant transformation in 10% of cases.
pecial mention should be made of the importance of the "H-zone" of the face. This designation, roughly in the shape of an "H," is defined by the preauricular regions and ear helices, nasolabial folds, columella and nose and lower eyelids. BCC lesions located in this area are associated with both a higher risk of recurrence and greater morbidity as a consequence of treatment.
There are several modalities available for the treatment of BCC. For a given lesion, one must weigh the treatment in terms of effectiveness in eliminating the malignancy against the functional and cosmetic implications before choosing the appropriate route. First, surgical excision involves the full-thickness removal of the lesion, down to subcutaneous fat, along with a rim of "normal" tissue. Current literature recommends margins of 3 mm for small (<10 mm) and 5 mm for larger (10-20 mm) BCC of the face. For lesions found in any other location, margins of 5 mm are recommended.
These wounds are typically either closed primarily or allowed to heal by secondary intention. For lesions located in delicate areas of the face, such as the eyelids, where removal of a margin of normal tissue may have profound functional consequences, Mohs micrographic surgery may be indicated. This technique has demonstrated the highest cure rates of any treatment modality. Cure rates of 99% for primary BCC and 93-98% for recurrent BCC have been demonstrated with the use of Mohs surgery.
An additional accepted treatment is cryotherapy, which is typically followed by curettage and healing by secondary intention. Local anesthesia is used, and the lesion is rapidly frozen with liquid nitrogen. There is no histological control with this method, and the tissue typically becomes initially very edematous. Its use has been advocated particularly near underlying cartilage. Recurrence rates of 3.7-7.5% have been reported.
Curettage and electrodessication have been employed in the past, with recurrence rates of 3.3% for low risk lesions to 18.8% for high risk ones. Due to unacceptably high recurrence rates, poor cosmetic outcome and lack of histological control, it is generally not accepted as a first line therapy for BCC. Radiation therapy has also been used to treat BCC, but the risk of radiation dermatitis, increased risk for future skin malignancy, and lack of histological control have discouraged its current use.
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