Epidermoid Cyst

Epidermoid cyst refers to the benign cyst that appears from the upper portion of a hair follicle and is encapsulated into a thin layer of epidermis-like epithelium. These cysts are usually filled with lipid-abundant debris and keratin.

Epidermoid cysts often affect adults, especially young and middle-aged individuals. Men have a higher prevalence than women in developing epidermoid cysts.

Certain genetic disorders, such as basal cell naevus syndrome and Gardner syndrome, contribute to the development of multiple epidermoid cysts.

Causes

Generally, epidermoid cysts arise from the occluded pilosebaceous unit. The non-hair-bearing sites of the body, such as the palms of the hands and the soles of the feet, can also be affected by epidermoid cysts as a result of traumatic implantation of epidermal cells in the dermis, where keratin is present in the epithelium-lined sac.

Clinical Features

The epidermoid cyst presents as a firm, fair or yellowish coloured, round papule or nodule attached to the surface of the skin. It can also be mobile throughout deeper layers. The diameter varies between 1 and 3 centimetres. A central punctum is present and can produce foul-smelling cheesy debris.

Epidermoid cysts usually appear on the central trunk of the body, affecting the chest and shoulders, as well as the face. These cysts are typically asymptomatic and can appear either alone or in multiples.

If the cyst ruptures its contents into the dermis, redness, swelling, and tenderness will result. Rupturing can occur as a result of trauma or bacterial infection, such as Escherichia coli and Staphylococcus aureus.

In rare cases, cutaneous squamous cell carcinoma can arise within an epidermoid cyst.

Diagnosis

An epidermoid cyst is diagnosed clinically. Biopsy is not usually required; however, the lesion can be surgically excised either for cosmetic reasons or due to complications.

Treatment

The majority of small and uncomplicated epidermoid cysts do not require medical intervention. The most effective treatment is surgical excision. Complete removal of the cyst reduces the rate of recurrence, though this can be challenging to achieve since the cyst may rupture during the procedure. Surgical excision carries risks of bleeding, scarring, and secondary bacterial infection. If the cyst ruptures or the capsule has not been completely excised, the cyst may reappear.

If infection develops, antibiotics, incision, and drainage may be used.

Epidermoid cysts are usually benign and grow slowly.