Cysts
Epidermoid
cyst (syn. sebaceous cyst,
wen)
These cysts contain keratin and its breakdown products, surrounded by a
wall of stratified squamous keratinising epithelium (the commonly used term sebaceous
cyst is incorrect — these cysts only rarely have associated sebaceous
glands and do not contain sebum). Epidermoid cysts often have a punctum. They
are inherited in an autosomal dominant fashion. The common sites are the face,
neck, shoulders and chest, areas favoured by acne vulgaris. Lesions may be
solitary but are commonly multiple. They enlarge slowly and may become inflamed
and tender from time to time. Suppuration may occur. The contents of an infected
cyst become semiliquid and usually very foetid. Recurrent infective episodes
cause the cyst wall to become adherent to surrounding subcutaneous tissue, and
consequently more difficult to remove. If ulceration occurs it can resemble
squamous cell carcinoma to which the term ‘Cock’s peculiar tumour’ may be
applied (Fig. 13.15). The contents of a cyst sometimes escape slowly from the
duct orifice and dry in successive layers on the skin, forming a ‘sebaceous
horn’ (Fig. 13.16). Treatment is by surgical excision (except if inflamed,
when it is better incised and drained). This can be performed under local
anaesthesia; an ellipse of skin including the punctum is removed with the cyst.
Unless the wall is completely removed, recurrence is likely.
Pilar
cysts
Pilar cysts are usually multiple and occur on the scalp, and they have
no punctum. Histologically, their lining is similar to the external root sheath
of the hair follicle.
Implantation
dermoids
Implantation dermoids may result from deep implantation of a fragment of
epidermis by a penetrating injury. Traumatic inclusion cysts usually appear on
the palmar or plantar surfaces of the hands, or on the buttocks or knees.
Callosities,
corns and warts
Callosity (French: ‘callosite’) is a localised thickened or
hardened part of skin which is an acquired, superficial, circumscribed,
yellow—white, flat, thickened patch of hyperkeratotic material. They occur at
the regions of pressure or friction on the hands and feet and they are usually
not painful. They are commonly occupational, occurring, for instance, on a
gardener’s hands. There is no need for treatment, although paring may be
necessary and should be carried out by a fully trained chiropodist.
Corn
(Old French: corn = grain) is a horny induration of the cuticle with
a hard centre, caused by undue pressure, chiefly affecting toes and feet. They
are circumscribed, horny thickenings, cone-like in shape with their apex
pointing inwards and their base on the surface. They occur at sites of
frictional pressure and usually will spontaneously disappear when the
aetiological factor is removed. Skilled treatment is important in patients with
diabetes or with a poor peripheral circulation when a secondary infection may
precipitate gangrene.
Wart
(Old English: wearte) is a dry, rough excrescence on the skin (Fig.
13.17). It is a virus-induced tumour that undergoes spontaneous resolution.
Transmission is by direct or intimate contact, the virus material usually being
inoculated through an abrasion. It is well recognised that patients with immune
deficiencies develop widespread resistant warts. They tend to occur on sites of
trauma, such as the beard area, hands, genital region and feet. All warts first
appear as small, smooth nodules often more easily palpable than seen. Warts are
more common in children and young adults, but can be present at any age, causing
pain and even difficulty in mobility. Plantar warts occur on the sole and are
usually multiple. They may be so tender as to render standing or walking
exceedingly uncomfortable. Treatment ranges from folk remedies to sophisticated
modern techniques, but the important factor remains that there is no 100 per
cent cure. Surgical removal is contraindicated as it leads to scarring
Venereal
warts and moist warts (papillomata acuminata) occur in the genital region.
Herpes
simplex is a viral skin infection that is recurrent in about I per cent of
the population. An immunosuppressed patient may show dissemination with viraemia
and may become seriously ill, requiring treatment with acyclovir infusions.
Topical or oral acyclovir is available for the treatment of localised disease.
Orf
is caused by the virus that produces pustular dermatitis in sheep. Those
infected will have been in contact with sheep in one form or another. The
lesions are usually single but may be multiple. The initial lesion is a dusky
red papule that enlarges to 1—2 cm in diameter and then resembles a large
domed pustule. This is a self-limiting condition that resolves in 5—8 weeks.