Published on 19/03/2015 by admin
Filed under Dermatology
Last modified 19/03/2015
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James M. Spencer and Brooke M. Walls
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Basal cell carcinoma (BCC) is a slow-growing malignancy originating in the epidermis. It most commonly arises in areas chronically exposed to UV light, especially the head and neck. Although it is very rare for BCC to metastasize, it can produce significant local tissue destruction, including cartilage and bony invasion.
Basal cell carcinoma slowly but relentlessly grows larger and deeper, and therefore therapeutic intervention is geared towards complete eradication of all malignant cells. Local recurrence is the consequence of inadequate therapy. Complete eradication is especially important because recurrent tumors are often larger and more aggressive than the original, incompletely treated primary tumor. Although complete eradication is the primary goal, the therapy chosen should achieve this with the maximal preservation of function and the optimal cosmetic result. Most often, therapy uses destructive techniques such as cryotherapy or curettage and electrodesiccation (C&D); more complex tumors may be treated by excisional surgery, Mohs surgery, or radiation therapy. The decision about which therapy to use is best made by considering four factors: tumor size; location; histology; and history (recurrent vs primary). When assessing a tumor, the clinician may wish to consider each of these four factors and decide whether the patient is high risk or low risk for each, to determine whether to use a simple or complex therapeutic strategy.
Most BCCs are discovered as primary tumors when they are still less than 1 cm in diameter. Generally tumors smaller than 1 cm on the face and 2 cm on the body are low risk.
Histologic growth pattern is a separate risk factor. The cytology of BCC does not vary: that is, all BCCs have well-differentiated, relatively monomorphic cell populations, and these tumors are not graded the way other malignancies are. However, the pattern of growth is variable and makes a large difference in choosing therapy. One must consider whether the tumor has a circumscribed or a diffuse growth pattern. Basal cell carcinoma most typically exhibits a circumscribed, cohesive growth pattern known as nodular. Nodular BCCs may show partial differentiation towards other structures, such as cystic or keratotic, but these variants are without therapeutic significance because the growth pattern is still nodular. Morpheaform, micronodular, infiltrating and superficial BCCs are all variants that exhibit a diffuse growth pattern. These lesions are more likely to recur as a result of subclinical extension or more aggressive tumor behavior, or both. Unfortunately, all too often biopsy reports come back to the clinician and simply state ‘BCC’, with no information about the growth pattern. Inadequately treated nodular BCC often recurs with a more aggressive diffuse growth pattern, such as infiltrating or micronodular.
Location is also an important variable to consider when choosing which therapy to use. Basal cell carcinoma tends to occur in chronically sun-exposed sites, especially the head and neck. Approximately 80% occur on the head and neck, and fully 25% occur on the nose. The central portion of the face, which has the highest incidence of BCC, contains the eyes, nose, and mouth, structures of functional and cosmetic importance highly vulnerable to the destructive effects of BCC. These same structures are also highly vulnerable to the destructive effects of therapy directed against BCC. The center of the face extending onto the area around the ears defines a roughly H-shaped area known as the H zone. Tumors in this zone have the highest recurrence rate and thus deserve special therapeutic attention. This zone also contains the most vulnerable structures and has the highest rate of BCC occurrence. Tumors near the ear canal, in the H zone, are of special concern. Extension down the ear canal provides the tumor with access to the brain and other intracranial structures, and when there is evidence of ear canal invasion particularly aggressive therapy is warranted.
Lastly, tumor history is important to consider. Recurrent tumors are more difficult to treat than primary tumors and require more aggressive methods.
When confronted with a BCC, the clinician may wish to consider these four variables in the context of the individual patient. The patient’s overall medical status, medical history, and age may influence the therapeutic decision making.
Biopsy with adequate dermal component
An adequate biopsy is critical in assessing the tumor. The tumor growth pattern is important information that is impossible to determine if only a superficial fragment is submitted to the laboratory. Deep shave, punch, incisional or excisional biopsy can all give sufficient dermis for such an evaluation. Because metastasis is so rare, no further evaluation is warranted.
A number of non-invasive imaging technologies are being investigated to delineate tumor depth and extent preoperatively and thus guide treatment. These include confocal microscopy, infrared spectroscopy, and ultrasound, but these all remain experimental and are not part of routine care.
Rarely, a BCC may have been neglected and reached a size such that direct bony invasion has occurred. If this is strongly suspected, a preoperative CT scan should be considered.
The possibility that patients with a BCC have an increased risk of developing subsequent internal malignancies has been suggested over the years, and remains controversial. At present there is no recommendation for extraordinary evaluation for internal malignancies beyond routine medical care in patients with a history of BCC.
Milan T, Pukkala E, Verkasalo PK, Koskenvuo M, Pukkala E. Int J Cancer 2000; 87: 283–8.
A total of 71 924 patients with a diagnosis of BCC were followed during the study period. There was a statistically significant increased risk of developing non-cutaneous malignancies in patients who had a BCC.
Bower CP, Lear JT, Bygrave S, Etherington D, Harvey I, Archer CB. J Am Acad Dermatol 2000; 42: 988–91.
A cohort of 13 961 patients diagnosed with BCC between 1981 and 1988 were followed for additional malignancies. There was a significant increased risk of subsequent melanoma, but no increased risk for internal malignancies.
Further complicating the relationship of BCC to other cancers is the argument that vitamin D provides chemoprevention for some visceral cancers. Specifically, it has been theorized that elevated levels of vitamin D lower the incidence of a variety of tumors, including breast, colon, and prostate cancers. As vitamin D is manufactured in the skin following exposure to UVB, it has been suggested that those with high UVB exposure should have a higher incidence of BCC but a lower incidence of breast, colon, and prostate cancers, among others.
Soerjomataram I, Louwman WJ, Lemmens VE, Coebergh JW, de Vries E. Am J Epidemiol 2008; 167: 1421–9.
Patients (n = 26 916) with skin cancer (n = 4089 squamous cell carcinoma, n = 19 319 BCC, and n = 3508 melanomas) from the Netherlands were identified during the years 1972–2002 and analyzed for their incidence of colorectal and breast cancers. SCC, and BCC of the head and neck only, were associated with a lower incidence of colorectal cancer, but not breast cancer. Patients with melanoma had a higher incidence of breast cancer.
The effect of vitamin D on cancer incidence remains controversial.
Silverman MK, Kopf AW, Grin CM, Bart RS, Levenstein MJ. J Dermatol Surg Oncol 1991; 17: 720–6.
This retrospective study of 2314 primary BCCs treated by C&D at a university dermatology clinic reports a 13.2% 5-year recurrence rate following C&D. Further analysis showed that size and location were important variables, with 5-year recurrence rates varying from 9.5% in low-risk locations to over 16.3% in high-risk sites. Similarly, 5-year recurrence rates ranged from 8.5% for tumors 0–5 mm in diameter to 19.8% for tumors 20 mm or more.
Rowe DE, Carroll RJ, Day CL. J Dermatol Surg Oncol 1989; 15: 315–28.
Reviewed literature since 1947, and reported a weighted average 5-year recurrence rate of 7.7% of primary BCCs treated with C&D.
Rowe DE, Carroll RJ, Day CL. J Dermatol Surg Oncol 1989; 15: 424–31.
Reports an almost 40% 5-year recurrence rate of recurrent tumors treated by C&D, emphasizing that this modality is not appropriate for recurrent tumors.
Extensive retrospective studies exist supporting the utility of this simple, rapid, and inexpensive method to treat BCC. However, prospective studies directly comparing C&D with other therapeutic modalities are lacking, and drawing conclusions from retrospective studies not controlled for size, histology, location, and history makes comparisons impossible.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
Curettage and electrodesiccation
Cryosurgery
Excisional surgery
Mohs micrographic surgery
