Breast Cyst: Causes, Symptoms & Treatment in Canada

A breast cyst is a fluid-filled sac that develops inside breast tissue, and it is one of the most common breast concerns among Canadian women. Many women discover one or more breast cysts during their lifetime, and the experience can understandably feel alarming. However, these lumps are almost always benign — meaning non-cancerous — and they frequently resolve on their own without any medical intervention.

What Is a Breast Cyst and Should You Be Concerned?

Understanding breast cyst symptoms is the first step toward peace of mind. Cysts are most often found in women between the ages of 30 and 50, though they can occur at any age. In Canada, where breast health screening is widely accessible through provincial healthcare programs, getting a proper diagnosis is straightforward. This article covers what causes breast cysts, how doctors diagnose them, and what treatment options are available to Canadians.

What Is a Breast Cyst?

Types of Breast Cysts: Characteristics and Management

Type of Breast Cyst	Characteristics	Who Is Affected	Management Approach
Simple Breast Cyst	Round or oval, fluid-filled sac with smooth walls; clearly defined edges on ultrasound; typically benign	Most common in women aged 35–50; frequently associated with hormonal fluctuations	Often requires no treatment; monitoring with regular clinical breast exams; aspiration if painful or large
Complicated Breast Cyst	Contains internal echoes or debris on ultrasound; not purely fluid-filled; borders may appear slightly irregular	Women of reproductive age; may develop from simple cysts over time	Short-term follow-up ultrasound (6–12 months); aspiration or biopsy may be recommended to rule out atypical cells
Complex Breast Cyst	Thick walls, internal septations, or solid components; higher likelihood of requiring further investigation	Women of any age; less common than simple or complicated cysts	Biopsy (fine needle aspiration or core needle) typically recommended; surgical removal considered if findings are suspicious
Microcyst	Very small cysts (under 2–3 mm); often clustered together; usually detected incidentally on imaging	Common in perimenopausal women; often associated with fibrocystic breast changes	Usually monitored with routine screening mammography; no intervention needed unless symptoms develop
Galactocele	Milk-filled cyst; smooth, well-defined; may feel firm or fluctuant depending on milk composition	Occurs in breastfeeding or recently postpartum women; relatively rare	Often resolves with cessation of breastfeeding; aspiration performed if cyst causes discomfort or does not resolve

A breast cyst is a small, round or oval pocket filled with fluid inside the breast. It can feel like a soft grape or a water-filled balloon. Sometimes it feels firm, which can make it harder to tell apart from other lumps.

Breast cysts are most common in women between the ages of 30 and 40. They tend to disappear naturally after menopause. However, women who take hormone therapy after menopause may continue to develop them.

Having a breast cyst — or even several — does not increase your risk of breast cancer. Most cysts need no treatment at all. That said, it is always important to get any new breast lump checked by a healthcare provider.

Types of Breast Cysts

Doctors generally divide breast cysts into two types based on their size.

• Microcysts are too small to feel with your fingers. They are usually found by chance during a mammogram or ultrasound done for another reason.
• Macrocysts are large enough to feel. They can grow to about 2.5 to 5 centimetres across. A large macrocyst can press on surrounding breast tissue and cause pain or discomfort.

Both types form the same way and are generally harmless. Understanding which type you have helps your doctor decide on the best course of action.

What Causes a Breast Cyst?

Each breast contains between 15 and 20 lobes of glandular tissue, arranged much like the petals of a daisy. These lobes divide into smaller lobules, which produce milk during pregnancy and breastfeeding. Tiny ducts carry milk toward a reservoir just beneath the nipple. Deep supportive tissue called stroma holds this whole structure together.

A breast cyst forms when overgrowth of glandular or connective tissue blocks one of these ducts. The blocked duct fills with fluid and becomes a cyst. The exact reason this happens is not fully understood.

Some evidence suggests that excess oestrogen in the body may play a role in cyst development. This would explain why cysts are so common during the reproductive years and tend to shrink after menopause. For more on how hormones affect breast health, see Health Canada’s women’s health resources.

Symptoms of a Breast Cyst

Many breast cysts cause no symptoms at all. Others are found during a routine breast exam or imaging test. When symptoms do appear, they may include:

• A smooth, easily movable lump with clear edges
• Breast pain or tenderness near the cyst
• A lump that grows larger and feels more tender in the days before your period
• A lump that shrinks and becomes less painful after your period ends

The way a breast cyst changes with your menstrual cycle is actually a helpful clue. This hormonal pattern is a strong sign that a lump is a cyst rather than something more serious. However, only a doctor can confirm the diagnosis.

It is worth noting that breast tissue naturally feels uneven or lumpy in many healthy women. Therefore, a new lump, a lump that changes, or any lump that concerns you deserves professional attention.

When to See a Doctor

You should contact your family doctor or visit a walk-in clinic if you notice any of the following:

• A new lump in your breast that you have not felt before
• A lump that has grown larger or changed in texture
• Nipple discharge, especially if it contains blood
• Breast pain that does not improve after your period
• Skin changes on your breast, such as redness, dimpling, or puckering

Your family doctor is a great first stop. They can assess the lump and refer you for an ultrasound or other imaging if needed. If you do not have a family doctor, a walk-in clinic can start the process. Most provincial health plans in Canada cover breast imaging when it is referred by a doctor.

Remember: finding a lump is scary, but most breast lumps in women of reproductive age turn out to be benign. Getting checked quickly brings peace of mind. As always, speak with your doctor before drawing any conclusions about your own health.

How Doctors Diagnose a Breast Cyst

Diagnosis usually begins after a doctor or the patient herself notices a lump during a physical exam. The process typically involves one or more of the following steps.

Clinical Breast Exam

Your doctor will examine both breasts carefully, feeling for lumps and checking for other changes in the tissue or skin. They will ask when you first noticed the lump, whether it has changed, whether it hurts, and how it behaves around your period.

A physical exam alone cannot confirm whether a lump is a cyst. In most cases, your doctor will recommend at least one additional test.

Breast Ultrasound

An ultrasound is often the first imaging test used for a breast lump, especially in younger women. A radiologist — a doctor who specialises in medical imaging — uses sound waves to create a picture of the inside of the breast.

On an ultrasound, a fluid-filled cyst looks quite different from solid tissue. A clearly fluid-filled area usually confirms a simple breast cyst. A solid mass, on the other hand, may suggest a fibroadenoma or, less commonly, cancer. For more information on breast imaging, visit the Mayo Clinic’s guide to breast cysts.

Fine Needle Aspiration

Fine needle aspiration (FNA) is a simple procedure where a doctor inserts a thin needle into the lump and draws out fluid. If fluid comes out and the lump disappears, this confirms a breast cyst on the spot.

In most cases, no further testing is needed after a successful aspiration. However, if the fluid contains blood, or if the lump does not disappear completely, the fluid may be sent to a lab for analysis. A solid area may require a small tissue sample — called a biopsy — to rule out cancer.

Mammography is not usually the first test chosen for a breast cyst, particularly in younger women. However, a doctor may recommend it if they suspect the lump has another cause.

Treatment Options for a Breast Cyst

The good news is that most simple breast cysts need no treatment. Your doctor may simply recommend monitoring the cyst over time to see whether it resolves on its own.

Watchful Waiting

If the cyst is small, painless, and not causing any problems, your doctor may suggest leaving it alone. Many cysts shrink and disappear without any intervention, especially after a menstrual cycle or two.

Your doctor may schedule a follow-up appointment four to six weeks later to check whether the cyst has changed. This approach is safe and avoids unnecessary procedures.

Fine Needle Aspiration as Treatment

Fine needle aspiration can both diagnose and treat a breast cyst in the same appointment. Once the doctor draws the fluid out of the cyst, the lump typically collapses and disappears.

Ultrasound guidance is often used to help position the needle accurately. If the fluid is clear or straw-coloured and the lump is gone after the procedure, no further treatment is required. Your doctor may recommend a follow-up check in four to six weeks to make sure the cyst has not come back.

Recurring Breast Cysts

Some breast cysts come back after aspiration, or new ones develop nearby. This is common and does not necessarily mean something is wrong. Recurring cysts can be drained again as needed.

If a cyst keeps returning and is causing significant pain or discomfort, your doctor may refer you to a breast surgeon or a radiologist for further evaluation. In rare cases, surgical removal may be considered. According to Healthline’s overview of breast cysts, surgery is very rarely necessary for a simple cyst.

Frequently Asked Questions About Breast Cysts

Key Takeaways

• A breast cyst is a benign, fluid-filled sac in breast tissue. It is not cancer.
• Breast cysts are most common in women aged 30 to 40 and often disappear after menopause.
• Symptoms can include a smooth movable lump, breast tenderness, and changes linked to your menstrual cycle.
• Diagnosis involves a physical exam, ultrasound, and sometimes fine needle aspiration.
• Most simple breast cysts need no treatment. Fluid can be drained if the cyst is painful or large.
• Having breast cysts does not increase your risk of breast cancer.
• Always see your family doctor or a walk-in clinic if you notice a new or changing breast lump. Most provincial health plans cover the necessary follow-up care.
• This article is for informational purposes only. Please speak with your doctor or a qualified healthcare provider for advice about your specific situation.