Chapter 083. Cancer of the Skin (Part 9)

Squamous Cell CarcinomaThe natural history of SCC depends on both tumor and host characteristics. Tumors arising on actinically damaged skin have a lower metastatic potential than those on protected surfaces. The metastatic frequency of cutaneous SCC, reported at 0.3–5.2%, occurs most frequently in regional draining lymph nodes. Tumors occurring on the lower lip and ear have metastatic potentials approaching 13 and 11%, respectively. The metastatic potential of SCC arising in scars, chronic ulcerations, and genital or mucosal surfaces is higher. The overall metastatic rate for recurrent tumors may approach 30%. Large, poorly differentiated, deep tumors, with perineural or lymphatic...
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Chapter 083. Cancer of the Skin (Part 9) Chapter 083. Cancer of the Skin (Part 9) Squamous Cell Carcinoma The natural history of SCC depends on both tumor and host characteristics.Tumors arising on actinically damaged skin have a lower metastatic potential thanthose on protected surfaces. The metastatic frequency of cutaneous SCC, reportedat 0.3–5.2%, occurs most frequently in regional draining lymph nodes. Tumorsoccurring on the lower lip and ear have metastatic potentials approaching 13 and11%, respectively. The metastatic potential of SCC arising in scars, chroniculcerations, and genital or mucosal surfaces is higher. The overall metastatic ratefor recurrent tumors may approach 30%. Large, poorly differentiated, deeptumors, with perineural or lymphatic invasion, often behave aggressively. Multipletumors with rapid growth and aggressive behavior can be a therapeutic challengein immunosuppressed patients. Nonmelanoma Skin Cancer: Treatment Basal Cell Carcinoma The most frequently employed treatment modalities for BCC includeelectrodesiccation and curettage (ED&C), excision, cryosurgery, radiation therapy,laser therapy, Mohs micrographic surgery (MMS), topical 5-fluorouracil, andtopical immunomodulators. The mode of therapy chosen depends on tumorcharacteristics, patient age, medical status, preferences of the patient, and otherfactors. ED&C remains the method most commonly employed by dermatologists.This method is selected for low-risk tumors (e.g., a small primary tumor of a lessaggressive subtype in a favorable location). Excision, which offers the advantageof histologic control, is usually selected for more aggressive tumors or those inhigh-risk locations or, in many instances, for aesthetic reasons. Cryosurgeryemploying liquid nitrogen may be used for certain low-risk tumors but requiresspecialized equipment (cryoprobes) to be effective for advanced neoplasms.Radiation therapy, while not used as often, offers an excellent chance for cure inmany cases of BCC. It is useful in patients not considered surgical candidates andas a surgical adjunct in high-risk tumors. Younger patients may not be goodcandidates for radiation therapy because of the risks of long-term carcinogenesisand radiodermatitis. Despite rapidly advancing technology in laser development,their long-term efficacy in treating infiltrative or recurrent lesions is still unknown.On the other hand, MMS, a specialized type of surgical excision that permits thebest histologic control and preservation of uninvolved tissue, is associated withcure rates >98%. It is the preferred modality for lesions that are recurrent, in ahigh-risk location, or large and ill-defined and where maximal tissue conservationis critical (e.g., the eyelids). Topical 5-fluorouracil therapy should be limited tosuperficial BCC. New topicals, the immunomodulators, show promise in theirefficacy at treating superficial and even nodular BCCs. Imiquimod, a relativelywell-tolerated cream, has successfully undergone phase III clinical trials.Intralesional chemotherapy (5-fluorouracil and INF) and photodynamic therapy(which employs selective activation of a photoactive drug by visible light) havebeen used successfully in patients with numerous tumors. A topical endonuclease(T4N5 liposome lotion) has been shown to repair DNA and may decrease the rateof NMSC in xeroderma pigmentosum. Squamous Cell Carcinoma The therapy of cutaneous SCC should be based on an analysis of riskfactors influencing the biologic behavior of the tumor. These include the size,location, and degree of histologic differentiation of the tumor as well as the ageand physical condition of the patient. Surgical excision, MMS, and radiationtherapy are standard methods of treatment. Cryosurgery and ED&C have beenused successfully for premalignant lesions and small primary tumors. Metastasesare treated with lymph node dissection, irradiation, or both. 13-cis-retinoic acid (1mg orally every day) plus INF-α (3 million units subcutaneously orintramuscularly every day) may produce a partial response in most patients.Systemic chemotherapy combinations that include cisplatin may also be palliativein some patients. Prevention As the vast majority of skin cancers are related to chronic UV radiationexposure, patient and physician education could dramatically reduce theirincidence. Emphasis should be placed on preventive measures beginning early inlife. Patients must understand that damage from UV-B begins early, despite thefact that cancers develop years later. Regular use of sunscreens and protectiveclothing should be encouraged. Avoidance of tanning salons and midday (10A.M.–2 P.M.) sun exposure is recommended. Precancerous and in situ lesions shou ...