What is an Epidermoid Cyst?
The so-called “fat cyst” or “sebaceous cyst” is actually called an epidermoid cyst. It consists of a sac-shaped proliferation, of benign origin, of keratinocytes (the cells that make up the superficial part of the skin or epidermis). Under normal conditions, keratinocytes, as they age, scale their remains – composed of keratin, a protein – to the outside. This process is perfectly normal and occurs daily in our skin while it is peeling.
If instead of being able to scale to the outside, the keratin is included within this sac of keratinocytes, an epidermoid cyst is formed. As we can see, it actually contains keratin – a protein – and not fat or sebum. Therefore, the terms fat cyst or sebaceous cyst are incorrect.
What does a “fat cyst” or epidermoid cyst look like?
They are usually asymptomatic, and manifest as subcutaneous plaques or nodules (“lumps”) with a normal skin surface. It is not uncommon for their follicular opening (comedo or pimple) to be observed on it, through which keratin can drain if squeezed. On palpation they are usually relatively soft and can fluctuate. Occasionally they become inflamed or infected, becoming red, edematous, painful and with an increase in size. Spontaneously or with manipulation, when they are inflamed or infected they drain keratin, blood and/or pus. Usually the smell they expel is usually nauseating.
Epidermoid cysts are usually located on the back, chest, or face, although they can appear anywhere on the body with hairy skin (for practical purposes, anywhere except the palms, soles, and mucous membranes themselves).
Do cysts require treatment?
In general, no. They are benign lesions and usually asymptomatic, so unless they become inflamed, they do not usually cause any discomfort beyond aesthetics. However, it is common for the patient to dislike the appearance of the epidermoid cyst or for it to bother with the rubbing of clothing or when sitting and opt for its removal.
How do you remove “fat cysts”?
The epidermoid cyst is a subcutaneous lesion, therefore they are under the skin. Consequently, they cannot be removed by applying a cream or any topical product. Likewise, the fact of squeezing their contents only empties them, but by not removing the cyst wall (of proliferating cells) it remains unscathed and reforms. To eliminate the epidermoid cyst definitively, the capsule must be removed.
How is the cyst capsule removed?
Classic excision is performed by surgery under local anaesthesia: the skin is opened, the entire lesion is removed and the defect is sutured. The main drawback of this technique is the size of the incision (which is usually larger than the nodule) and that suturing with thread can and usually leaves a scar. Also taking into account that epidermoid cysts tend to settle in areas of more difficult healing (dorsal area, chest, neck), surgery can encourage keloids or hypertrophic scars to appear.
However, excision has recently been described using a small hole made with CO2 laser, recommended for mobile cysts and smaller than 1.5 cm in size. A hemostatic mosquito is introduced through the hole and the cyst capsule is separated to be removed later. The resulting hole is allowed to close for a second intention if it is small, or sutured if it is larger. By means of this technique, the size of the scar is smaller (linear or punctate).
What are the advantages of removing an epidermoid cyst with a CO2 laser?
The advantage is exclusively aesthetic: the resulting scar is smaller and less voluminous than that performed by standard surgery. In terms of cure or relapse rate, the result is the same with either technique.
Can all fat cysts be removed with CO2 laser?
No. Only those that are less than 1.5 cm in diameter and that are mobile (little adhered to deep planes). Otherwise, this technique does not have any advantage over conventional surgery. CO2 laser is usually used for cysts in especially noble areas such as the face, neck or décolleté.
REFERENCES
Song SW, Burm JS, Yang WY, Kang SY. Minimally Invasive Excision of Epidermal Cysts through a Small Hole Made by a CO2 Laser. Arch Plast Surg. 2014 Jan; 41(1):85-8.
ACKNOWLEDGEMENTS
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