A Sebaceous cyst appear as a superficial skin lump that tends to bulge onto the skin. It is often associated with a small bluish pin-point dot on the surface which corresponds to a punctum. A Sebaceous cyst is a benign and non-cancerous cyst.
A Sebaceous cyst is also known as an Epidermal cyst. It arises from the follicular infundibulum, which is one of the cell layers forming the skin. The cyst contains a cheesy greyish material which is composed of Keratin, one of the components of the most superficial layer of the skin. The cyst contents are encapsulated by a thin layer of cyst wall formed by the follicular infundibulum.
The term ‘Sebaceous cyst’ is actually incorrect as it erroneously refers to the origin as the Sebum glands while the term ‘Epidermal cyst’ is the medically correct term as the actual cyst arises from the follicular infundibulum which is part of the epidermal layer. Nonetheless, this article will use the term ‘Sebaceous cyst’ to avoid confusion.
Sebaceous cysts can occur any part of the skin, including the face, torso and limbs. It can occur singly or in multiples spread over different parts of the body. Sebaceous cysts should not be painful or tender.
A Sebaceous cyst and a Trichilemmal cyst are very similar in appearance. They both appear as superficial skin lumps that are easily palpable. There are two main differences between these two types of cysts, namely the cell origin and the location that they manifest.
Sebaceous cysts can occur on any part of the skin but Trichilemmal cysts occur almost exclusively on the scalp. In contrast to Sebaceous cysts, Trichilemmal cysts arises from the root sheath of the hair follicle, which is essentially the base of the scalp hair.
The subsequent discussion on Sebaceous Cyst applies to Trichilemmal cysts too.
Sebaceous cysts are benign and do not become cancerous. However, this assessment can only be made when the lump is removed and undergoes a histological examination (microscopic examination).
A Sebaceous cyst can be considered for removal if the cyst is causing inconvenience to the individual, if infected or if the individual just wants it removed for peace of mind and histological assessment
A Sebaceous cyst, particularly if enlarged, can cause inconvenience while doing daily activities. The cyst can catch on clothing or jewelry. In addition, a cyst may get bumped on during daily activities or when on crowded public transport.
Sebaceous cysts can also get inflamed with subsequent secondary bacterial infection. Cysts get inflamed if a hard knock had or if an individual had it squeezed, causing the keratin contents to leak out and irritating the skin. An inflamed cyst can easily swell up to twice its usual size or larger with a red and angry appearance. At this stage, it can potentially be secondarily infected by bacteria with formation of pus.
It is perfectly reasonable to leave small Sebaceous cysts alone. However, it is important to be aware that a Sebaceous cyst, unlike a pimple or comedone (whiteheads and blackheads), must never be squeezed or have any attempt made to express it. The keratin contents, as mention above, will lead to inflammation and infection.
Most Sebaceous cyst excisions are carried out under local anesthesia as the cyst is usually located superficially in the skin. It is important that the cyst is removed in its entirety with no cyst wall remaining behind. Any cyst wall that is left behind can lead to recurrence of the sebaceous cyst.
Local anesthesia is injected around the cyst to allow the surgery to be carried out. An incision is made over the cyst, taking care to include the punctum (bluish pin-point) which is part of the cyst wall that is attached to the skin surface. The cyst is then dissected out carefully and removed in its entirety. The skin is then sutured with absorbable sutures that do not require removal of stitches. The skin will usually have united quite nicely by the two week mark.