Basal Cell Carcinoma

Introduction

Basal cell carcinoma (BCC) is the most common type of skin cancer. It rarely metastasizes but it is still malignant.

If left untreated BCC's can cause significant destruction by invading into normal adjacent tissues (rodent ulcer). Caucasians living in sunny areas have a 30% lifetime risk of developing a BCC.

It occurs mainly in fair-skinned patients.

There is frequently a family history of this cancer.

Sunlight is a factor in about two-thirds of these cancers while one-third occur on areas of the body that are not exposed to sunlight, emphasizing the genetic susceptibility of basal cell cancer patients. The head and neck is the most location for a BCC, however they may occur anywhere on the body in particular areas of increased sun exposure. Basal cell carcinomas many also occur as part of an inherited syndrome called nevoid basal cell carcinoma syndrome (Gorlin's syndrome).

Presentation & diagnosis

Patients may present with a shiny, pearly slightly reddened nodule. This classical presentation enables an easy diagnosis. However, superficial basal cell cancer can present as a red patch like eczema. Infiltrative or morpheaform basal cell cancers can present as a skin thickening or scar tissue making it difficult to distinguish basal cell cancer from acne scar, actinic elastosis or recent cryo-destruction inflammation. A clinical diagnosis is often correct, however the differential diagnosis includes other more aggressive skin cancers. Diagnosis may require a skin biopsy for histological examination. This process is usually achieved under local anesthesia. Basal cell carcinomas may be divided into different subtypes (nodular, micronodular, cystic, infiltrative, morphoeic, pigmented, superficial) based on the gross or histological appearance. It is not unusual to encounter morphologic features of several variants of basal cell cancer in the same tumour. The sub-type of BCC is one factor that can influence the treatment that is recommended. With this knowledge definitive treatment can be planned.

Treatment

There are a number of treatment options available The main factors that will influence the recommended treatment are the sub-type, location and size of the BCC. Others factors to be considered are the general state of health of the patient and if the lesion is a recurrence of previously treated BCC.

Complete surgical excision is the recommended option in the majority of cases. A high cure rate can be achieved by complete excision with a narrow margin of normal tissue. The resulting wound will then be reconstructed in the most appropriate fashion. Direct closure of the wound may be possible or alternatively depending on the size and location of the wound a skin graft or flap procedure can be utilised. The excised tissue is examined by a pathologist. It is essential to obtain a histological diagnosis and gain information about the resection margins.

Superficial basal cell carcinoma are responsive to topical chemotherapy such as Aldara (Imiquimod) or Efudix (5-Fluorouracil). This is the only type of basal cell cancer that can be effectively treated with topical chemotherapy.

Electrodessication and curettage, cryotherapy and laser ablation are sometimes suggested. The disadvantages of these techniques are that destruction of the tissue does not allow pathological examination of the removed lesion and hence information regarding the diagnosis and the adequacy of the margins is not available. The wound will also heal by a process of scarring.

Mohs micrographic surgery is a surgical technique that does allow for tissue examination. It can have a high cure rate. The technique is very time-consuming and utilised indiscriminately offers no advantage over standard surgical technique. The appropriate application of this technique is limited to areas where an adequate excision margin is difficult to achieve.

Photodynamic therapy is a new modality for treatment of BCC's, which is administrated by application of photosensitizers to the target area. When these molecules are activated by light, they become toxic, therefore destroy the target cells.

Radiation therapy is generally used in older patients who are not candidates for surgery. Basal cell carcinomas are responsive to radiation therapy. Less damage to normal tissues occurs when the radiation is delivered in incremently doses. Up to 25 individual treatment visits may be required. A major draw back is that if surgery were subsequently required, healing of surgical wounds in a previously irradiated area is much more difficult. For difficult tumours surgery followed by radiation is usually recommended.

Prognosis

Prognosis is excellent if the appropriate method of treatment is used in early primary basal cell cancers. Recurrent and large tumours are much harder to cure. Although basal cell carcinoma rarely metastasizes, it grows locally with invasion and destruction of local tissues.

Squamous cell carcinoma

Introduction

Squamous cell carcinoma (SCC) is the second most common type of skin cancer (after basal cell carcinoma). The sun-UV radiation damage to skin is cumulative and is the most commonly implicated risk factor for the development of SCC. Other risk factors include therapeutic radiation, immunosuppressant drugs and diseases, chemical toxins (arsenic) and chronic wounds and scars. The risk of metastatic spread is low (less than 5%) but the risk increases with tumour size (>2cm diameter), depth of invasion, immunosuppressant drugs and tumours of the lips and ears and those tumours occurring at the sites of chronic wounds and scars.

Presentation & Diagnosis

Squamous cell carcinoma most often occur in sun exposed areas. There is often general evidence of sun damage to the surrounding skin, with multiple actinic keratoses (solar keratoses). The commonest sites for these to occur is on the back of the hands and forearms and the front of the legs. The clinical appearance is highly variable however SCC often begin as a small asymptomatic nodule. As they enlarge the center becomes necrotic and sloughs. The nodule turns into an ulcer with hard raised edges. The tumour will gradually invade into deeper structures if left untreated. The risk of invasion into deeper structures and metastasis increases with tumour size.

Treatment

For the majority of SCC the most appropriate treatment is complete surgical excision and reconstruction by an appropriate method. Direct wound closure may be possible or a more complex reconstruction may be required (skin graft or flap reconstruction). The excised tissue is examined by a pathologist. This will provide information about the exact diagnosis, the adequacy of the excision margins and the extent of invasion into the deeper tissues. Further treatment can be planned, although not usually required if required, this may include more extensive surgery and radiotherapy. If metastasis to the lymph nodes does occur, surgical removal of the lymph nodes (lymphadenectomy) of that region is recommended.

The use of topical chemotherapy is generally limited to premalignant (actinic keratoses) and insitu lesions. Aldara (Imiquimod) or Efudix (5-Fluorouracil) are both effective topical agents for early lesions. Photodynamic therapy is also only appropriate for premalignant lesions. Photosensitizing agents are applied to the target area. When these molecules are activated by light, they become toxic and therefore destroy the target cells.

Radiation therapy is a primary treatment option for patients in whom surgery is not feasible and is an adjuvant therapy for those with metastatic or high-risk cutaneous SCC. Currently systemic chemotherapy is used exclusively for patients with metastatic disease.

Prognosis

The prognosis is generally good when appropriate treatment is undertaken early. Patients must remain extremely vigilant following the treatment of a skin cancer as the risk factors that were implicated initially often remain unchanged.

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