Section 8 of 8
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Histologically it is composed of islands and smaller nests of basaloid cells with peripheral palisading. There are often many mitoses and apoptotic bodies, the latter explaining why most basal cell carcinomas grow slowly. Aggressive variants (the infiltrating and micronodular types) occur. The following variants follow in order:
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SQUAMOUS CELL CARCINOMA is the second most common form of skin cancer (after BCC) in Caucasians. There is a predisposition for the sun-damaged skin, particularly of fair-skinned people who tan poorly. Most arise in areas of direct exposure to the sun. Non-exposed areas are occasionally affected. They may arise in burns scars or chronic sinuses. In some sites, HPV has been incriminated. They present as shallow ulcers, often with a keratinous crust and some elevation. A clinical and microscopic photograph follow.
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Squamous cell carcinomas have the potential to metastasise (in BCC’s it is only 1 in 20,000). It is variable, depending on site and underlying pathology. For example those arising in solar keratoses and sun-damaged skin have less metastatic potential (probably less than 0.5%) than those arising in non sun-damaged skin (2%), the lip (approximately 10%), osteomyelitic sinuses (30%), burn scars (18%) and radiation-induced (20%). A higher rate of metastasis also applies to the vulva, penis and oral mucosa. In SCC’s of the lip, adverse histological features include thickness above 6mm, perineural infiltration and the tumour grade.
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The keratoacanthoma is usually a solitary, pink, dome-shaped nodule with a central keratin plug. It grows rapidly to a size of 1-2 cm over a period of 1-2 months, and has a tendency to involute spontaneously after 3-6 months. It may cause destruction (in the nose and lip region) before it regresses and therefore active treatment is recommended. They occur in older persons. The lower leg is a frequent site. A clinical photograph follows.
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The merkel (neuroendocrine) cell carcinoma is a rare, but highly aggressive small cell carcinoma of the skin. It appears to be solar related in some cases. A clinical and microscopic photograph follow.
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The dermatofibroma is a not uncommon dermal tumour of uncertain histogenesis. It present as an indurated lesion or sometimes a papulo-nodular lesion. It may contain haemosiderin pigment. It often appears lightly pigmented. A clinical photograph follows.
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This lecture covers most skin lesions. It is a lot to absorb in one sitting. You should return to it from time to time to learn more, in the light of your clinical encounters.
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