Cyst: Definition, Types & Treatment

Instructor: Kathryn Davis
A cyst is a closed sac of tissue filled with gas, fluid or other material. This lesson will explain the characteristics of a cyst and highlight some of the many different types of cysts as well as various treatments for them.

What is a Cyst?

My friend Gary (not his real name) was brushing his teeth one evening when he noticed a small, painless lump on the inside of his lower lip. Gary ignored the lump at first, assuming it was just a common canker sore. However, a couple of weeks later the lump was still there, and it appeared to be growing. Fearing the worst, Gary went to see his doctor.

Gary's doctor performed a biopsy just to be safe, but told him the lump was most likely a cyst in one of his minor salivary glands (the very small salivary glands located all around the inside of the mouth). A cyst is a closed sac of tissue. It may be filled with a variety of materials, including fluid, gas or semisolids. Gary's cyst was probably caused by a sialolith, or tiny calcium stone, that formed inside his salivary gland and blocked the entrance, stopping the flow of saliva out of the gland.

The biopsy results confirmed that Gary's lump was indeed a harmless cyst, so his doctor recommended a wait-and-see approach, telling Gary that the cyst would most likely go away on its own. It did, and within a few weeks Gary no longer had a lump on the inside of his lip.

Types of Cysts

Cysts can occur in any tissue in the human body. They may be so small that they cannot be seen without a microscope, or so large that they affect the placement of internal organs. True cysts are encased by epithelial tissue, whereas pseudocysts are encased by granulation or connective tissue.

Because cysts can occur anywhere in the body, there are hundreds of different types of cysts. Although there are far too many types to list, some of the more common cysts include:

Sebaceous cysts which form in hair follicles or sebaceous glands in the skin

An inflamed cyst in a sebaceous gland on the back of the neck
Photo of an inflamed sebaceous cyst on the back of the neck

Ovarian cysts that sometimes occur in women when fluid builds up in the ovary because an egg is not released properly during ovulation

Ultrasound photo of an ovarian dermoid cyst
Ultrasound photo of a dermoid cyst on an ovary

Chalazia or swellings in the eyelid caused by a blocked oil gland

A chalazion, or cyst on the eyelid caused by a blocked meibomian gland
Photo of a chalazion, or cyst on the eyelid

The majority of cysts, like Gary's blocked salivary gland, are benign. However not all cysts are harmless. For example, a type of ovarian cyst in women known as a dermoid cyst can sometimes develop into malignant squamous cell carcinoma, although this is rare and only happens in 1-2% of cases.

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