Page 410 - Medicine and Surgery

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406 Chapter 9: Dermatology and soft tissues

is often visible. If there is a superimposed infection the Aetiology
lump may become red, hot and tender. It is thought that there is herniation of synovial tissue
from a joint capsule or tendon sheath. The ganglion has
afibrous capsule and contains mucoid material.
Management
Uninfected cysts are excised under local anaesthesia,

if required using an elliptical incision. Clinical features
Infected cysts are first incised and drained. Excision
Aganglion may present as a swelling or pain commonly
is performed if still necessary once the infection has around the wrist or the dorsum of the hand. On exami-
been treated. nation the swelling transilluminates.

Management
Dermoid cysts
Ganglia may resolve or may be recurrent. Aspiration and
Definition injection of a crystalline steroid may be useful, and in-
Acyst arising from deep implanted epidermal cells. jection of hyaluronidase into the lesion prior to aspira-
tion may improve results. Surgical removal is effective,
although recurrence may still occur.
Aetiology/pathophysiology
Dermoid cysts arise from epidermal cells, which have
been implanted into the dermis either during embry- Skin tumours
onic development or following trauma. They are lined
with squamous epithelium and contain sebum, cells and
occasionally hair. Basal cell carcinoma
Definition
Clinical features Basal cell carcinoma (BCC) is a locally invasive skin can-
Cysts present as soft rubbery swellings deep to the skin. cerarising from the basal layer of epidermis.
There may be fixation to the deep tissues.
Congenital dermoid cysts are found at sites of embry- Incidence

onic fusion. The commonest congenital dermoid cyst Approximately 75% of all skin tumours.
occurs at the junction between the frontal bone and
the maxilla at the lateral border of the orbit (external Age
angular dermoid). Increases in incidence with age.
Implantation cysts occur following traumatic im-

plantation of epidermal cells. The surrounding skin Sex
and subcutaneous tissue may be erythematous and M > F
swollen.
Geography
Management Most common in Caucasians, and uncommon in dark-
Dermoid cysts are surgically removed. Congenital der- skinned populations.
moid cysts require general anaesthesia due to the deep
extension. Aetiology
Basal cell carcinomas are predisposed to by light and
ionising radiation. Sun exposure is the most important
Ganglion
aetiological factor particularly in individuals with fair
Definition skin, pale eyes and red hair. Childhood sun exposure
Abenign cystic swelling occurring over a joint or tendon appears to be important, especially if there is repeated
sheath. intermittent intense exposure.