Why do cysts grow

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Last updated: April 8, 2026

Quick Answer: Cysts grow due to abnormal cell proliferation, fluid accumulation, or blockage of ducts, often triggered by genetic mutations, infections, or chronic inflammation. For example, ovarian cysts can reach 5-10 cm in diameter, while sebaceous cysts form when oil glands are blocked. Approximately 20% of women develop functional ovarian cysts during their reproductive years, with most resolving spontaneously within 2-3 menstrual cycles. Epidermoid cysts, common skin cysts, grow slowly at about 1-2 mm per year due to keratin accumulation.

Key Facts

Cysts are closed sac-like structures that can contain fluid, pus, or other material
Ovarian cysts affect approximately 20% of women during reproductive years
Sebaceous cysts form when oil gland ducts become blocked
Epidermoid cysts grow at approximately 1-2 mm per year
Most functional ovarian cysts resolve spontaneously within 2-3 menstrual cycles

Overview

Cysts are closed sac-like structures that can develop in various tissues throughout the body, containing fluid, pus, or other materials. The study of cysts dates back to ancient medical texts, with Hippocrates (460-370 BCE) describing cystic formations in his writings. Modern classification began in the 19th century with improved microscopy, allowing pathologists to distinguish between different cyst types. Today, cysts are categorized based on their location, contents, and cellular lining, with over 100 distinct types identified. Common examples include ovarian cysts (affecting approximately 20% of women), sebaceous cysts (blocked oil glands), and ganglion cysts (joint or tendon-related). The global prevalence varies by type, with skin cysts affecting millions worldwide annually. Diagnostic imaging advancements since the 1970s, particularly ultrasound and MRI, have revolutionized cyst detection and monitoring.

How It Works

Cyst growth occurs through several distinct mechanisms depending on the cyst type. Fluid-filled cysts typically develop when ducts or glands become blocked, preventing normal drainage and causing accumulation. For example, sebaceous cysts form when oil gland openings are obstructed, leading to sebum buildup that gradually expands the sac. In contrast, epithelial-lined cysts like epidermoid cysts grow through continuous keratin production by the cyst wall, expanding at approximately 1-2 mm per year. Functional ovarian cysts develop during the menstrual cycle when follicles fail to rupture properly, filling with fluid and potentially reaching 5-10 cm in diameter. Parasitic cysts, such as those caused by Echinococcus tapeworms (first described in detail in 1853), grow through larval multiplication within host tissues. Genetic mutations can trigger abnormal cell proliferation in neoplastic cysts, while inflammatory processes can create pseudocysts without epithelial lining through tissue damage and fluid encapsulation.

Why It Matters

Understanding cyst growth mechanisms has significant clinical implications for millions affected worldwide. Proper diagnosis prevents unnecessary interventions, as approximately 95% of ovarian cysts are benign and many resolve without treatment. However, cysts can cause serious complications when they rupture (potentially causing peritonitis), become infected, or compress adjacent structures—large brain cysts may increase intracranial pressure. Certain cysts have malignant potential; complex ovarian cysts with solid components have approximately 10-15% cancer risk in postmenopausal women. Treatment advances like laparoscopic cystectomy (minimally invasive removal) developed in the 1990s have reduced recovery time from weeks to days. Research into cyst formation pathways continues to inform new therapies, including hormonal treatments for recurrent ovarian cysts and improved drainage techniques for pancreatic pseudocysts.