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1. What is a sebaceous cyst?
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A sebaceous cyst (epidermoid cyst or wen) is a retention cyst produced by obstruction to the mouth of a sebaceous gland. Therefore sebaceous cysts may occur wherever sebaceous glands exist and are not found on the gland-free palms and soles. They are especially common on the scalp, face, scrotum and vulva and on the lobe of the ear. The cyst is fluctuant and cannot be moved separately from the overlying skin. There may be a typical central punctum and the contents are cheesy with an unpleasant smell. The lining membrane consists of squamous epithelium.
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2. Can a sebaceous cyst undergo malignant change?
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Yes, but this is very rare.
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3. What is a Cock's peculiar tumour?
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This is when a sebaceous cyst ulcerates, to resemble a fungating carcinoma
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4. What is a benign calcifying epithelioma?
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This is when a sebaceous cyst becomes calcified.
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5. How would you treat a sebaceous cyst?
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The uninfected sebaceous cyst should be removed to prevent possible complications. A small elliptical skin incision is made around the punctum of the cyst under local anaesthetic; the capsule is identified and the cyst removed intact. Failure to remove the cyst in its entirety may lead to recurrence. If the cyst is acutely inflamed, incision and drainage will be required, followed later by excision of the capsule wall.
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6. What are the two types of dermoid cyst?
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Implantation dermoids and sequestration dermoids.
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7. What is an implantation dermoid? What are the clinical features?
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This is a painless, subcutaneous, cystic swelling commonly found on the pulps of the fingers, attached neither to skin nor to the deeper structures. It usually follows a puncture injury (e.g. from a rose thorn) with consequent implantation of epithelial cells into the subcutaneous tissues. The cyst typically contains a white, greasy material, which results from degeneration of the desquamated cells. An old healed scar over the cyst may help confirm the diagnosis.
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8. What is a sequestration dermoid? What are the clinical features?
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This is a subcutaneous cystic swelling resulting from an embryological rest of epithelial cells along a line of fusion. The common sites are over the external angular process of the frontal bone (the external angular dermoid at the upper outer margin of the orbit), the root of the nose (internal angular dermoid) and in the midline. When in relation to the skull, the underlying bone is usually hollowed around it. The possibility of communication with an intracranial dermoid or the meninges should be excluded by skull radiography or computed tomography scan prior to excision.
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9. What is the alternative name for a wart?
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Verruca vulgaris.
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10. What are the characteristics of verruca vulgaris?
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Also known as a wart. This is a well-localized horny projection that is common on the fingers, hands, feet and knees, particularly of children and young adults. Crops of warts may occur on the genitalia and perianal region, in many cases spread by sexual contact. Warts are often multiple and are due to a number of different strains of human papilloma virus. Microscopically, there is a local hyperplasia of the prickle cell layer of the skin (acanthosis) with marked surface cornification.
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11. How would you treat verruca vulgaris?
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Untreated, warts usually vanish spontaneously within 2 years, hence the apparent efficacy of folklore ‘wart cures’. Often reassurance that these lesions will disappear is all that is required, but if treatment is demanded they can be burnt down by the application of a silver nitrate stick or podophyllin, frozen with liquid nitrogen, or curetted under local or general anaesthesia.
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12. What is the difference between a verruca and a wart?
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Plantar warts are otherwise known as verrucas, these occur on the weight-bearing areas of the foot. Pressure forces the wart into the deeper tissues, producing intense local pain on walking. They may occur in epidemics in schools and other such places, where the hygiene of the communal bath or changing room is not of a high standard. They should be treated by podophyllin or curettage.
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13. Which parts of the body are most commonly affected by keratoacanthoma?
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Sun-exposed areas such as the face and nose (75%).