What’s the Difference Between a Cyst and Tumor?

If you find a lump or bump somewhere on your body, you may wonder: Is this a cyst? Is it a tumor? What’s the difference? And what should I do?

“It’s quite common to find a lump or bump on your body. Most are unrelated to cancer. The first step, no matter what, is to not alarm yourself too much,” says Douglas Scott Micalizzi, MD, PhD. Dr. Micalizzi is an oncologist and clinical director of the Cancer Early Detection and Diagnostics Clinic at Mass General Cancer Center in Waltham. “Take a little time to ask yourself specific questions about what you’ve found. That will help you determine whether you need to seek medical attention.”

Dr. Micalizzi recommends that you seek prompt medical attention if you have other specific symptoms near a lump or bump. “If the area is painful, hot, red, or draining fluid, that is more concerning for an infection and you should call your doctor. But if it’s just a lump or a bump with no other symptoms, then it makes sense to watch the area for at least a couple of days or even a few weeks and see how it’s changing,” he explains.

Tumor vs. cyst

“People tend to think about cysts as more on the benign (noncancerous) side of the spectrum, and they may assume that tumors are always cancer. However, a tumor can be either benign or cancerous, and so can a cyst,” Dr. Micalizzi says.

A cyst is a sac like a balloon that’s filled with fluid, air or another substance. Cysts can occur when something blocks a gland or other bodily drainage. That causes the substance to get backed up, and the body builds a sac around the substance.

Cysts can appear anywhere on your body. Although they can be any size or shape, many are round, have smooth edges, and feel like they can roll around under your fingers.

“The majority of cysts are not related to cancer,” Dr. Micalizzi says. “A cyst is usually a benign condition. But they sometimes need to be drained or removed because they can cause symptoms.”

In contrast, tumors are typically more solid collections of tissue. They occur when cells grow uncontrollably when they shouldn’t, or when cells don’t die when they should.

Tumors can occur anywhere on or inside the body.

Types of cysts

There are hundreds of types of cysts, with many different possible causes. For example, a cyst may form when a milk duct in the breast is blocked, a hair follicle is damaged, or a gland under the skin is blocked. Some cysts are inside the body and can be caused by other medical conditions, like polycystic ovary syndrome (PCOS).

Some common types of skin cysts include:

• Epidermoid: Also called a sebaceous cyst, these form in the upper part of hair follicles and are usually filled with keratin, a type of protein found in your hair, skin, and nails. Epidermoid cysts usually have a small tip or point (punctum) and occur anywhere on the body but are most common on the face, neck, and torso.
• Ganglion: These cysts are filled with a mucus-like substance and form in the skin around your joints, usually on the hand and wrist but can be on the knee and foot. They may occur from repetitive motion or stress on certain joints, especially in sports like gymnastics.
• Trichilemmal: Trichilemmal cysts, or pilar cysts, mostly form on the scalp. They’re similar to epidermoid cysts because they form in hair follicles and are filled with keratin. However, they don’t have a punctum and usually occur in groups of firm, round nodules.

Types of tumors

There are three general types of tumor:

• Benign: A benign tumor may grow larger, but it stays in the same general area where it started. Benign tumors don’t contain any cancer cells and often don’t need treatment unless they’re causing bothersome symptoms.
• Premalignant: These tumors are not cancerous yet, but they can become malignant. They may be treated with a “watch and wait” approach, when a health care provider monitors you over time. Or they might require removal to decrease the chance that they will become malignant.
• Malignant: These tumors are cancerous. They can grow and spread (metastasize) to other areas of the body, and they require treatment.

How to tell if a lump is a tumor or cyst

If you find a lump or bump, you can ask yourself several questions. The answers will help you assess the situation and may help a health care provider determine next steps in deciding if it’s a cyst vs. tumor.

• Where is it on your body?
• Is the lump or bump very hard, or is it soft and squishy?
• Did you experience any injury or trauma to that area in the past few days? An injury, even a small accident you barely remember, might easily explain a lump or bump.
• Is it tender or painful to the touch? If yes, that might indicate an infection or other inflammation, as opposed to a tumor or cyst.
• Are you having any other symptoms, such as pain, itching, abnormally colored skin, fluid draining from the area, or fever? Again, these symptoms often are associated with infection, rather than a tumor or cyst.
• Is the lump or bump getting worse or getting better? Is it changing or staying the same? “A cancerous tumor doesn’t come and go,” Dr. Micalizzi says. “So if a lump or bump is persisting or getting bigger, you should make an appointment with your doctor.”

If you have signs of infection or if the lump gets larger in a short period of time, seek medical attention. But if not, Dr. Micalizzi recommends that you monitor the lump for a few days, or through an entire menstrual cycle if the lump is in your breast to determine if it goes away.

“If the lump persists, the first step would be to contact your primary care provider (PCP). They can help explore your concern and direct you on steps to get more information, such as a mammogram, imaging test, blood test, or biopsy.”

Finding a new lump or bump on your body can cause anxiety, but Dr. Micalizzi stresses that the vast majority of cysts and tumors are noncancerous. “I always encourage people to be self-aware of their bodies so that they recognize any changes that might indicate a health issue. Cancer is a rare diagnosis—it’s important not to jump to conclusions and assume that every lump or bump is cancer. But at the same time, don’t ignore things that are getting worse.”