Cysts and tumors are two common types of lumps. It can be hard to tell them apart because they’re often found in the same places. However, there are a few key differences between the two.

Finding a lump under your skin is alarming, but most of the time they’re harmless. If it’s a cyst, it is a small sac filled with air, fluid, or other material.

A tumor refers to any unusual area of extra tissue. Both cysts and tumors can appear in your skin, tissue, organs, and bones.

Sometimes you can have both such as ovarian cysts and ovarian tumors. If you’re concerned, your doctor can help you determine what you have and whether it is serious.

Most people’s first thought is cancer when they notice a new lump. While certain types of cancer can cause cysts, cysts themselves are almost always benign. Tumors, however, can be either benign or malignant. Benign tumors tend to stay in one place. Malignant tumors grow and may cause new tumors to develop in other parts of your body.

In most cases, you can’t tell the difference between a cyst and a tumor just by looking at them. However, there are a few things you can watch for to see whether it’s more likely to be a cyst or a tumor. Keep in mind that these aren’t strict rules, so it’s best to have your doctor take a look.

red and swollen
blackhead in center
white, yellow, or green discharge
able to move around under skin

Tumors can sometimes grow large enough that they put pressure on surrounding tissues. Depending on where your lump is located, you may experience additional symptoms, such as difficulty breathing, moving your joints, eating, or controlling your bladder. Contact your doctor as soon as possible if you notice a lump accompanied by unusual symptoms, even if they don’t seem related.

There are many types of cysts with a variety of causes. Some types are related to an underlying medical condition, such as polycystic ovary syndrome. Others form directly on your skin’s surface when dead skin cells multiply instead of falling off like they usually do. Other causes of cysts include:

Tumors are the result of abnormal cell growth. Usually, the cells in your body grow and divide to form new cells whenever your body needs them. When older cells die, they’re replaced by new ones. Tumors form when this process breaks down. Old, damaged cells survive when they should die, and new cells form when your body doesn’t need them. When these extra cells keep dividing, it may form a tumor.

Some tumors are benign, which means they form in only one spot without spreading to surrounding tissue. Malignant tumors are cancerous and can spread to nearby tissue. As cancerous tumors grow, cancer cells can break off and travel throughout the body, forming new tumors.

Sometimes doctors recognize cysts during a physical exam, but they often rely on diagnostic imaging. Diagnostic images help your doctor figure out what’s inside the lump. These types of imaging include ultrasounds, CT scans, MRI scans, and mammograms.

Cysts that look smooth, both to the naked eye and in diagnostic images, are almost always benign. If the lump has solid components, due to tissue rather than liquid or air, it could be either benign or malignant.

However, the only way to confirm whether a cyst or tumor is cancerous is to have it biopsied by your doctor. This involves surgically removing some or all of the lump. They’ll look at the tissue from the cyst or tumor under a microscope to check for cancer cells.

If the lump is filled with fluid, your doctor might use something called fine needle aspiration. They’ll insert a long, thin needle into the lump to pull out a sample of the fluid.

Depending on the location of the lump, most biopsies and aspirations are done in an outpatient setting.

Treatment for cysts and tumors depends entirely on what’s causing them, whether they’re cancerous, and where they’re located. However, most cysts don’t require treatment. If it’s painful or you don’t like the way it looks, your doctor can remove it or drain the fluid that’s within it. If you decide to drain it, there’s a chance the cyst will regrow and require complete removal.

Benign tumors also usually don’t need treatment. If the tumor is impacting a nearby area or causing other problems, you may need surgery to remove it. Cancerous tumors almost always require treatment with surgical removal, radiation therapy, or chemotherapy. In some cases, you may need a combination of these treatments.

While most cysts and tumors can wait until your next appointment with your doctor, let them know immediately if you notice that the lump:

  • bleeds or oozes
  • changes color
  • grows quickly
  • itches
  • ruptures
  • looks red or swollen

It’s often hard to tell the difference between a cyst and a tumor — even for doctors. While there are a few things you can look for to help you identify whether a lump is more likely to be a cyst or a tumor, it’s best to make an appointment with your doctor. They can take a small sample of the lump to determine whether it’s a cyst, tumor, or something else, and recommend the best course of treatment.