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Basal cell carcinoma (BCC) is the most common skin cancer in humans. They can be destructive and disfiguring. Risk is increased in people who have had high cumulative exposure to sunlight (specifically UV light) and/or particular chemicals (e.g. arsenic). Treatment is with surgery or local chemotherapy. It is rarely life- or limb-threatening.
Forms
Various forms are recognised:
- Nodular: flesh-colored papule with telangiectasis. If it ulcerates, it becomes a "rodent ulcer" (ulcus rodens), an ulcerating nodule with (often) a pearly border.
- Cystic: rarer and hard to distinguish from the nodular form. It has a central cavity with fluid.
- Pigmented: a variant of the nodular form that may be confused with melanoma.
- Sclerosing/cicratising: a scar-like lesion.
- Superficial: a red scaling patch
All forms are more likely to occur on areas of the body that have had high cumulative sunlight exposure. Actinic keratosis (sunlight-induced skin damage) may be present around the tumor.
Diagnosis
The gold standard for diagnosis is a biopsy. In small lesions, the tumor is generally removed in its entiriety, while larger ones are biopsied first and surgically removed later if the biopsy result has confirmed that it is malignant.
Pathophysiology
Basal cell carcinomas develop in the basal cell layer of the skin. Sunlight exposure leads to DNA crosslinking between thymidine residues. While DNA repair removes most UV-induced damage, not all crosslinks are excised. There is, therefore, cumulative DNA damage leading to mutations. Apart from the mutagenesis, sunlight depresses the local immune system, possible decreasing immune surveillance for new tumor cells.
Treatment
Most basaliomas are removed surgically. Margins of excision may be variable: sclerosing lesions may need a wider margin, as they develop processes that project outside the visible part of the tumor.
Some difficult cases respond to local therapy with 5-fluorouracil, a chemotherapy agent.
Prognosis
Basel cell carcinoma rarely metastasizes, but invades healthy tissue in the proximity. Rarely the cancer can impinge on vital structures and result in death. The vast majority of cases do not lead to any complications.
Epidemiology
It is much more common in fair skinned individuals and males (men more commonly work outdoors). In the United States alone there are more than 400,000 new cases yearly.
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