Yes, a dermoid cyst is a type of teratoma. Specifically, it’s the most common type: a mature cystic teratoma, meaning it’s a benign growth made of fully developed tissues. The two terms are used interchangeably in most clinical settings, though “dermoid cyst” technically refers to a specific subtype within the broader teratoma family.
How the Two Terms Relate
“Teratoma” is the umbrella category. It covers any tumor that contains tissues derived from all three layers of embryonic cells: the layers that eventually form skin and nerves, bones and muscle, and organs like the thyroid and intestinal lining. Within that category, teratomas are divided into two main groups: mature and immature.
Mature teratomas contain fully differentiated, adult-type tissue. They’re benign. Immature teratomas contain primitive, underdeveloped tissue (most often immature nerve cells) and are classified as malignant. The proportion of immature tissue determines the tumor’s grade, with grade 0 being a mature teratoma.
A dermoid cyst is a mature cystic teratoma where skin-derived components predominate. Skin-related tissues (hair, oil glands, keratin) are present in virtually all mature cystic teratomas, which is why most of them qualify as dermoid cysts. In practice, the terms are nearly synonymous.
What’s Actually Inside a Dermoid Cyst
These growths are famous for containing surprisingly recognizable body tissues in unexpected places. When surgeons open one, they commonly find hair, oily sebaceous material, keratin (the protein that makes up skin and nails), and fat. Some contain cartilage, bone fragments, or even thyroid tissue. Over 90% of cases include tissue from all three embryonic cell layers, not just skin.
The cyst wall is lined with normal-looking skin, complete with hair follicles and sweat glands. Inside, loose clumps called “floating balls” can form, containing mixtures of keratin, hair, fat, and old blood products. On imaging, the fat content is often what tips off a radiologist, since fat shows up distinctively on both ultrasound and MRI.
Where Dermoid Cysts Form
Location depends on how you define the term. Cutaneous dermoid cysts, the kind found on the head, neck, and face, form when skin cells get trapped along natural lines of fusion as an embryo develops. More than 8 out of 10 of these occur on the head and neck. They can also appear on the spine, around the eye socket, inside the nasal sinuses, or on the surface of the eye.
Ovarian dermoid cysts are the gynecological version and the one most people encounter in adulthood. These are true mature cystic teratomas arising from egg-producing germ cells in the ovary. Despite having the same name as the skin-surface type, ovarian dermoids have a different origin: they develop from reproductive cells rather than from trapped embryonic skin.
Complications to Be Aware Of
Most dermoid cysts cause no symptoms and are discovered incidentally during imaging for something else. When problems do occur with ovarian dermoids, the most significant risk is torsion, where the cyst causes the ovary to twist on its blood supply. This happens in about 5.6% of cases, with larger cysts carrying a higher risk. Torsion causes sudden, severe pelvic pain and requires emergency treatment.
Malignant transformation, where a benign dermoid develops into cancer, is rare. It occurs in roughly 0.17% to 2% of mature cystic teratomas, and when it does happen, about 80% to 85% of cases become squamous cell carcinoma. This risk is low enough that most dermoid cysts are managed based on size and symptoms rather than cancer concern.
How Dermoid Cysts Are Treated
Small, asymptomatic dermoid cysts can often be monitored over time. When removal is needed, the standard approach for ovarian dermoids is cystectomy, where the cyst is removed while preserving the ovary. This can be done through minimally invasive laparoscopic surgery or through a traditional open incision (laparotomy).
Laparoscopic removal offers shorter hospital stays and less blood loss, but it comes with a tradeoff: a higher chance of the cyst contents spilling into the abdominal cavity during removal, and a recurrence probability of about 7.6% within two years. Open surgery has a near-zero recurrence rate in the same timeframe. The spillage itself doesn’t appear to cause additional health problems, but the recurrence difference is something worth discussing with a surgeon when planning the procedure.
For cutaneous dermoid cysts on the head, neck, or face, surgical excision is straightforward and curative. These are typically removed in childhood when they become noticeable as firm, painless lumps along the brow line or near the scalp.