Skin cysts – should I be worried?

Cysts can come in all shapes and sizes and can appear all over the body. What are these strange lumps? Should you be worried about them? What are the differences between them? Leading plastic surgeon Mr Alastair MacKenzie Ross lends us his insight into the world of skin cysts.

What are the most common types of cyst?

The most common types of cysts vary according to the part of the body, but in normal skin, the most common cysts are epidermal or epidermoid cysts. These are often inappropriately referred to as “sebaceous cysts”; however, this is actually a misnomer (true sebaceous cysts are different and much less common). Epidermal cysts form when cells at the surface of the skin (epidermis) move deeper into the skin instead of shedding off. These cells produce a protein called keratin, which helps to strengthen and protect the surface of the skin; however, when the cells have moved deeper into the skin and continue to divide and multiply, the keratin they secrete becomes trapped in the middle of the sac of cells, appearing as a thick, yellowish, ‘cheesy’, substance, which may leak from the cyst if it is burst.

It can be difficult to tell the difference between an epidermal cyst and a lipoma (another common swelling under the skin made of fat tissue). However, it should be possible to see and feel where the cyst is attached to the skin – there is usually a small punctum or indent.

You can also get cysts is the scalp; however, they are not actually attached to the skin, but are almost free-floating, attached to hair follicles. These are called pilar or trichilemmal cysts.

A third form of common cysts are around the finger, toe or wrist joints. These are called ganglion cysts (referring to out-pouching of a joint), and are also commonly known as mucous cysts on the last joints towards the ends of finger or toes. Here, the joint lining moves to where it shouldn’t be.

Cysts can appear in other places, e.g. around the eye, and the lips.

Do they all look the same?

It depends on where they are. For example, finger cysts look different from cysts elsewhere on the skin. That said, many cysts can look similar.

Epidermal cysts can change appearance if they get infected – they become very red, painful, and hot. When this happens, they can become difficult to distinguish from an abscess. The cyst may split, and a cheesy material come out. Infections usually respond to antibiotics. After a treated infection the cyst become infected again. This is a reason to have it removed.

Can cysts be cancerous?

They can, but it’s very unusual. You can also have cancers that look like cysts – lumps under the skin can look like cysts but are actually cancer.

Are there any types of cyst that can be dangerous if not treated?

If it’s a proper cyst, it’s unlikely to be dangerous. However, cysts can grow. Some big cysts, especially in awkward places, such as around the eye, can cause pressure.

If cancer is mistaken for a cyst and left untreated, it can be dangerous – you should always have it checked to make sure it’s a cyst rather than just assuming it is.