Most cysts can grow over time, but whether yours will depends entirely on what type it is. Some cysts grow slowly for years, others swell and shrink repeatedly, and many dissolve on their own without any treatment. The behavior of a cyst is largely determined by where it is in your body and what’s driving its formation.
How Cysts Grow
A cyst is essentially a sac filled with fluid, semi-solid material, or air. Growth happens when the lining of that sac continues producing its contents faster than the body can reabsorb them. In skin cysts, the lining sheds protein (keratin) into the interior, slowly expanding the pocket. In organ cysts, cells lining the wall actively secrete fluid into the enclosed space, pushing the walls outward. The rate of this process varies enormously. Some cysts add fractions of a millimeter per year. Others can double in volume within months.
Skin Cysts: Slow but Steady
Epidermal cysts, the firm lumps that form just under the skin (often called sebaceous cysts), are among the most common types people notice and monitor. They range from about a quarter of an inch to over two inches in diameter and typically grow slowly. Some stay small and painless for years without changing at all. Others gradually increase in size and eventually become uncomfortable, especially if they press against clothing or sit in a spot that gets friction.
What catches people off guard is a sudden size increase. This usually isn’t true growth but inflammation or infection. The cyst becomes swollen, red, tender, and warm. If it ruptures beneath the skin, it can leak fluid into surrounding tissue and trigger a noticeable flare. A cyst that grows rapidly, becomes painful, or exceeds about 5 centimeters (2 inches) warrants evaluation, since fast growth is not typical for a benign skin cyst.
Ovarian Cysts: Many Shrink on Their Own
Functional ovarian cysts are the most common type in women of reproductive age, and the good news is that most of them resolve without treatment. Follicular cysts form when a follicle doesn’t release its egg and instead fills with fluid, generally reaching larger than 2.5 centimeters. Corpus luteum cysts form after ovulation and typically grow to about 3 centimeters. Both types usually disappear within one to three menstrual cycles.
The picture changes with cysts that don’t follow this pattern. If a cyst persists after several cycles, it’s unlikely to be functional, and further evaluation is needed. Cysts smaller than 10 centimeters that appear simple on ultrasound (one chamber, smooth walls, no solid areas) are generally benign regardless of age and can be monitored with repeat imaging. Cysts larger than 10 centimeters, or those with complex features like thick walls, solid components, or irregular borders, raise more concern and typically require closer investigation.
Size also affects the risk of complications. Ovarian cysts larger than 5 to 6 centimeters carry a higher risk of ovarian torsion, where the ovary twists on itself, cutting off blood supply and causing sudden, severe pain. This is a surgical emergency.
Ganglion Cysts: They Fluctuate
Ganglion cysts, those rubbery lumps that appear near wrist or hand joints, behave differently from most other cysts. Rather than growing in one direction, they tend to fluctuate in size. They often get larger with repetitive joint movement and may shrink during periods of rest. This waxing and waning pattern is one of their defining features. Over time, though, the general trend is often toward gradual enlargement. Many ganglion cysts eventually disappear on their own, but some persist for years.
Kidney Cysts: Continuous Growth in Some Conditions
Simple kidney cysts are extremely common, especially after age 50, and most never cause problems or grow significantly. Polycystic kidney disease (PKD) is a different story. In autosomal dominant PKD, cysts form throughout both kidneys and grow relentlessly over decades. Research tracking patients over 14 years found that both the number and volume of cysts more than doubled during that period. On average, total cyst volume increased by about 10% per year, and cyst count rose by about 7% per year. Patients started with an average of around 762 cysts and ended with roughly 1,715.
This steady, compounding growth is what eventually compromises kidney function in PKD. The expanding cysts compress and replace healthy tissue. Unlike functional ovarian cysts or ganglion cysts, kidney cysts in PKD do not resolve spontaneously.
What Determines Whether a Cyst Keeps Growing
Several factors influence a cyst’s trajectory:
- Type of cyst. Functional cysts (ovarian, some thyroid) are driven by hormonal cycles and often self-resolve. Structural cysts (epidermal, dermoid) lack that mechanism and tend to persist or slowly enlarge.
- Location. Cysts in enclosed organs like the kidneys have nowhere to drain and may continue accumulating fluid. Ganglion cysts near joints are influenced by physical activity and fluid pressure from the joint itself.
- Underlying condition. A single kidney cyst in an otherwise healthy person behaves nothing like the hundreds of cysts in PKD. The genetic or disease context matters enormously.
- Inflammation and trauma. Skin cysts that get squeezed, irritated, or infected can swell dramatically in days. This isn’t the same as organic growth, but it changes the size and symptoms in ways that feel identical to the person experiencing it.
Size Thresholds That Matter
For skin cysts, rapid growth or a diameter over 5 centimeters is considered a red flag worth investigating. For ovarian cysts, anything under 10 centimeters that looks simple on imaging is typically monitored conservatively. Cysts above 10 centimeters often require surgical removal, and those larger than 12 centimeters are more likely to need open surgery rather than a minimally invasive approach. Ovarian cysts with complex features at any size, including solid areas, thick internal walls, or increased blood flow on imaging, prompt further workup for malignancy.
For dermoid cysts (a specific type of ovarian cyst), the risk of cancerous transformation increases with age over 45, a diameter over 10 centimeters, and rapid growth on serial imaging. These are removed surgically when they’re large, symptomatic, or growing on follow-up scans.
If you’re tracking a cyst, the most useful thing you can do is note its size at each check and watch the trend over time. A cyst that stays the same size for a year or more is behaving very differently from one that doubles in six months, and that trajectory matters more than any single measurement.