Cysts

Overview

An epidermoid cyst is a benign cyst that arises from the upper portion of a hair follicle and is encapsulated within a thin layer of epidermis-like epithelium. These cysts are typically filled with lipid-abundant debris and keratin.

Epidermoid cysts are usually benign and grow slowly. They most commonly appear as a firm, round papule or nodule attached to the surface of the skin, ranging from a fair to yellowish colour, with a diameter typically between 1 and 3 centimetres. A central punctum is often present and may produce foul-smelling cheesy debris.

Causes and Risk Factors

Epidermoid cysts generally arise from the occluded pilosebaceous unit. On non-hair-bearing sites of the body, such as the palms of the hands and soles of the feet, these cysts may develop as a result of traumatic implantation of epidermal cells into the dermis, where keratin becomes enclosed within an epithelium-lined sac.

Epidermoid cysts most commonly affect adults, particularly young and middle-aged individuals. Men are more frequently affected than women. Certain genetic disorders, including basal cell naevus syndrome and Gardner syndrome, are associated with the development of multiple epidermoid cysts.

Signs and Symptoms

Epidermoid cysts most commonly appear on the central trunk, including the chest and shoulders, as well as on the face. They may present as a single lesion or in multiples and are typically asymptomatic. The cyst may also be mobile through the deeper layers of skin.

If the cyst ruptures and releases its contents into the dermis, redness, swelling, and tenderness may result. Rupture can occur due to trauma or bacterial infection, including organisms such as Escherichia coli and Staphylococcus aureus.

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

Diagnosis

An epidermoid cyst is diagnosed clinically based on its characteristic appearance. A biopsy is not usually required; however, the lesion may be surgically excised either for cosmetic reasons or when complications have developed.

Treatment Options

The majority of small and uncomplicated epidermoid cysts do not require medical intervention. When treatment is indicated, surgical excision is the most effective approach. Complete removal of the cyst reduces the likelihood of recurrence, though this can be challenging to achieve given the risk of intraoperative rupture.

Surgical excision carries potential risks including bleeding, scarring, and secondary bacterial infection. If the cyst ruptures or its capsule is not completely removed, recurrence is possible.

When infection is present, treatment may include antibiotics, incision, and drainage.

When to Seek Medical Attention

Medical attention should be sought if a cyst becomes red, swollen, painful, or begins to discharge, as these signs may indicate infection or rupture. A cyst that is enlarging, changing in character, or causing significant cosmetic concern warrants evaluation by a dermatologist. A referral from a family physician is typically required to access dermatology services at the Centre for Medical and Surgical Dermatology.