A cystic teratoma is a benign ovarian growth that contains a surprising mix of body tissues, including hair, fat, skin, and sometimes even teeth or bone. Also called a dermoid cyst, it is the most common type of ovarian germ cell tumor, accounting for 10 to 20% of all ovarian masses. These growths develop from reproductive cells (germ cells) that can differentiate into almost any tissue type, which is why the contents can seem so unusual.
Why It Contains Hair, Teeth, and Bone
A cystic teratoma forms from cells capable of developing into the three fundamental tissue layers of the human body: the ectoderm (which normally produces skin and nerves), the mesoderm (which forms muscle, bone, and cartilage), and the endoderm (which lines internal organs). Because these cells retain that broad developmental potential, the resulting cyst can produce a disorganized collection of tissues that would otherwise never appear together. Inside a single cyst, surgeons commonly find oily fluid (sebum), clumps of hair, fatty tissue, cartilage, and fragments of bone or teeth. The tissues are mature and well-differentiated, meaning they look and behave like normal adult tissue, just in the wrong place.
The term “dermoid cyst” comes from the fact that skin-like (ectodermal) tissue dominates in most cases. Ectodermal components are present in virtually all mature cystic teratomas. When pathologists describe these growths formally, “mature cystic teratoma” and “dermoid cyst” are used interchangeably.
Who Gets Them
More than 80% of mature cystic teratomas are diagnosed during the reproductive years, with a median age at diagnosis of about 30. In one large retrospective study of over 2,000 patients, the heaviest concentration fell in the 20 to 39 age range, though cases have been documented in patients as young as 7 and as old as 82. They can occur in one or both ovaries, and bilateral cases carry a higher risk of recurrence after treatment.
Symptoms and How They’re Found
About 20% of mature cystic teratomas cause no symptoms at all and are discovered incidentally during an ultrasound, a pregnancy scan, or surgery performed for an unrelated reason. When symptoms do appear, they depend largely on the size of the cyst.
Smaller teratomas may cause a dull, chronic pelvic pain or a sense of pressure in the lower abdomen. Larger ones can produce more noticeable abdominal pain, a feeling of fullness, and occasionally a mass you or your doctor can feel during a physical exam. In 5 to 10% of cases, the first sign is sudden, severe abdominal pain caused by ovarian torsion, where the weight of the cyst causes the ovary to twist on its blood supply. This is a surgical emergency.
How It’s Diagnosed
Ultrasound is typically the first imaging tool used, and cystic teratomas have a distinctive appearance. The mix of fat, fluid, and solid tissue creates a characteristic pattern on imaging. Radiologists often look for a feature called a Rokitansky nodule, a solid bump projecting into the cyst cavity that may contain teeth, bone, or dense tissue. The combination of fatty fluid and calcified structures makes these cysts relatively easy to identify compared to other ovarian masses.
If ultrasound findings are ambiguous, MRI can provide more detail and help distinguish a benign teratoma from something more concerning. Blood tests measuring tumor markers like alpha-fetoprotein (AFP) and beta-hCG are sometimes drawn. Normal levels of these markers help confirm the growth is benign and guide surgical planning.
Treatment: Surgery That Spares the Ovary
Laparoscopic surgery is the standard treatment for mature cystic teratomas. The approach has shifted significantly over the years. Historically, the entire ovary was removed (oophorectomy), but ovary-sparing surgery, where the cyst is carefully peeled away from healthy ovarian tissue (cystectomy), is now the preferred option for most patients. This is especially important for younger patients who want to preserve fertility.
Ovary-sparing surgery is considered appropriate when preoperative bloodwork rules out malignancy, meaning AFP and beta-hCG levels fall within normal ranges. If the cyst has caused the ovary to twist, surgeons will typically relieve the torsion in an initial procedure and then plan a second surgery to remove the cyst once they confirm it’s benign.
The surgery itself is minimally invasive in most cases. Multiple small incisions are used to access the cyst laparoscopically, and recovery is generally quicker than with open surgery.
Recurrence After Surgery
Cystic teratomas can come back. A study tracking young women for five years after surgery found that 11.2% of those who had cystectomy (cyst removal only) experienced a recurrence. Interestingly, the recurrence rate was actually higher, 20.3%, in women who had the entire ovary removed. This likely reflects the fact that oophorectomy was chosen for more complex or larger tumors to begin with.
Two factors significantly predict recurrence after cystectomy: large tumor size at the time of the original surgery and having teratomas in both ovaries. Women with either of these risk factors had roughly 2.5 times the likelihood of recurrence within five years. Follow-up imaging is a practical way to catch any new growth early.
Ovarian Torsion and Other Complications
The most serious acute complication is ovarian torsion, reported in 3 to 16% of patients with ovarian teratomas. The cyst adds weight to the ovary, making it more likely to rotate and cut off its own blood supply. Torsion causes sudden, intense pain on one side of the pelvis, often with nausea and vomiting, and requires emergency surgery to save the ovary.
Rupture of the cyst is another possible complication, though less common. If the oily contents spill into the abdominal cavity, they can trigger chemical peritonitis, an inflammatory reaction that causes significant pain and may require surgery to clean out.
Risk of Becoming Cancerous
Malignant transformation of a mature cystic teratoma is very rare. When it does happen, more than 80% of cases involve squamous cell carcinoma developing from the skin-like tissue within the cyst. The remaining cases transform into carcinoid tumors or adenocarcinomas. Distinguishing a teratoma that has undergone malignant transformation from a standard benign one before surgery is extremely difficult because the cyst’s complex mix of tissues makes imaging interpretation challenging. The median age for malignant transformation is around 33, somewhat older than the typical age at diagnosis. The overall rarity of this complication is one reason routine removal of asymptomatic teratomas is sometimes debated, though most clinicians lean toward surgical removal to eliminate the risk entirely.