A dermoid tumor is a type of growth that contains a surprising mix of body tissues, including hair, skin, fat, and sometimes even teeth or bone. These tumors develop from germ cells, the same cells that would normally go on to form eggs or sperm, which is why they can produce such a wide variety of tissue types. Most dermoid tumors are benign, and the most common type by far is the ovarian dermoid cyst, also called a mature cystic teratoma.
Why Dermoid Tumors Contain Hair and Teeth
Dermoid tumors trace back to very early development in the embryo. They originate from primordial germ cells, which are special cells that begin forming during the first weeks of embryonic life. These germ cells have a unique ability: they carry the potential to differentiate into virtually any type of body tissue. Under normal circumstances, they migrate to the developing gonads and eventually become eggs or sperm.
Sometimes, though, these cells go off course. Instead of following their normal developmental path, they begin multiplying and differentiating on their own, producing a disorganized collection of tissues. A single dermoid tumor can contain skin with hair follicles, sebaceous glands that produce oily material, cartilage, bone fragments, and nerve tissue. This random assortment of mature tissues is what sets dermoid tumors apart from other types of cysts or growths, and it’s also what makes them look so unusual on imaging or during surgery.
Common Locations
The ovary is the most frequent site. Ovarian dermoid cysts account for 69% of ovarian germ cell tumors in young women and about 11% of all ovarian tumors. They’re typically diagnosed during the reproductive years, with a median age in the mid-30s, though they’ve been found in patients ranging from 13 to 76 years old. About 8 to 15% of cases are bilateral, meaning cysts develop in both ovaries.
In children, dermoid cysts most often appear in the head and neck region, making up as much as 84% of all dermoid cysts in pediatric patients. The eyebrow area is the single most common spot, followed by the orbit (the bony socket around the eye), the scalp, neck, and ear. These typically show up as a small, firm, painless lump that grows slowly. Most are noticed before age 3.
Less common locations include the brain (intracranial dermoid cyst) and the spine (spinal dermoid cyst). These are rare but can cause more serious problems depending on their size and position.
Symptoms of Ovarian Dermoid Cysts
About 20% of ovarian dermoid cysts cause no symptoms at all and are discovered incidentally during an ultrasound or pelvic exam done for other reasons. When symptoms do appear, the most common is chronic pelvic pain or a feeling of pressure in the lower abdomen. Larger tumors may produce a noticeable abdominal mass, increased pelvic pressure, or irregular bleeding.
Acute, sudden pain is a red flag. It occurs in 5 to 10% of cases and is most often caused by ovarian torsion, where the weight of the cyst causes the ovary to twist on itself, cutting off its blood supply. Torsion is diagnosed in roughly 20% of women who undergo surgery for dermoid cysts. Younger women appear to be at higher risk for this complication, though cyst size alone doesn’t reliably predict it. Torsion has been found in cysts as small as 5.5 centimeters and as large as 10 centimeters or more.
In rare cases, ovarian dermoid cysts containing thyroid tissue can produce thyroid hormones, leading to symptoms of hyperthyroidism like rapid heartbeat and weight loss. An even rarer complication is a neurological condition called NMDA encephalitis, a severe brain inflammation that can cause confusion, seizures, and psychiatric symptoms.
Symptoms in the Brain and Spine
Spinal dermoid cysts grow slowly but can eventually compress the spinal cord or nearby nerves. This may lead to difficulty walking, weakness in the arms or legs, and loss of bladder control. Intracranial dermoid cysts can cause headaches, vision problems, or seizures depending on where they sit within the brain. Both types are uncommon but tend to require surgical treatment when they become symptomatic, because the pressure on neural structures can cause lasting damage if left untreated.
How Dermoid Tumors Are Diagnosed
Ultrasound is usually the first imaging tool used, especially for ovarian dermoid cysts. These tumors have a characteristic appearance: they often contain a solid nodule called a “dermoid plug” that presses against the cyst wall, along with echoes from hair, fat, or bits of calcium. More than half of dermoid plugs on ultrasound are associated with visible hair or calcium deposits. The nodules are typically round, range from about 1.5 to 4 centimeters, and produce a bright (hyperechoic) signal that helps distinguish them from other types of ovarian cysts.
When ultrasound findings are unclear, CT or MRI can help. Fat within the cyst is a strong diagnostic clue, since few other tumors contain fat in this way. For dermoid cysts in the brain or spine, MRI is the primary imaging method because it provides the best detail of soft tissue structures.
What Happens if a Dermoid Cyst Ruptures
Rupture is uncommon but potentially serious. The contents of a dermoid cyst, particularly the oily sebum and hair, are highly irritating to the tissue lining the abdominal cavity. When these materials leak out, they can trigger chemical peritonitis, an intense inflammatory reaction that mimics a severe abdominal infection. Symptoms include fever, rapid heart rate, dehydration, and widespread abdominal inflammation visible on CT scans.
The inflammatory response can be dramatic. In documented cases, it has caused fat necrosis, microabscesses, and granulomatous inflammation (clusters of immune cells walling off the foreign material). The pattern of inflammation can even be mistaken for cancer on imaging, with nodular deposits scattered across the abdomen that look similar to metastatic disease. This makes ruptured dermoid cysts a genuine diagnostic challenge and often requires surgery to clean out the spilled contents and confirm what happened.
Cancer Risk
The vast majority of dermoid tumors are benign. Malignant transformation occurs in only 1 to 2% of cases. When it does happen, the most common cancer type is squamous cell carcinoma, arising from the skin-like tissue within the cyst. A large study tracking all mature cystic teratoma cases over an eight-year period found a malignant transformation rate of 1.2%. This risk is generally higher in older patients, particularly those over 45, which is one reason doctors may recommend removal rather than monitoring in that age group.
Surgical Treatment
Surgery is the standard treatment for dermoid tumors that are growing, causing symptoms, or large enough to pose a risk of torsion or rupture. For ovarian dermoid cysts, laparoscopic surgery (using small incisions and a camera) is the preferred approach. It was first described for dermoid removal in 1989 and has largely replaced open surgery for most cases, offering better visualization, less invasiveness, and shorter hospital stays.
The most common procedure is cystectomy, which removes just the cyst while preserving the rest of the ovary. This accounts for about 57% of surgeries. In other cases, the entire ovary is removed (36%) or a partial removal is performed (about 6%). The choice depends on the patient’s age, whether they want to preserve fertility, and what the surgeon finds during the operation. Surgeons typically extract the cyst inside a bag to prevent its contents from spilling into the abdomen, reducing the risk of chemical peritonitis.
Conversion from laparoscopic to open surgery is uncommon, happening in fewer than 5% of cases, and is usually prompted by an unexpected finding like a suspicious tissue sample or an injury during the procedure. For dermoid cysts in the brain or spine, the approach depends entirely on location and accessibility, and neurosurgical planning with MRI is essential before any intervention.
Small, asymptomatic ovarian dermoid cysts can sometimes be monitored with periodic ultrasounds rather than removed immediately, particularly in younger patients. The decision between watching and operating depends on the cyst’s size, growth rate, and the patient’s individual circumstances.