Understanding Dermoid Cysts: Ovarian vs. Congenital

It is an often unsettling experience to hear that you or your child has a “dermoid cyst,” especially when a doctor mentions it might contain hair, skin, or even teeth. While these findings sound unusual, they are well-documented medical occurrences that are almost always benign (non-cancerous) ^[1][2].

The first thing to understand is that “dermoid cyst” is an umbrella term. Doctors use it to describe two very different conditions that happen for different reasons and in different parts of the body.

One Name, Two Different Conditions

The confusion often starts with the name. To determine which type you are dealing with, look at the location (and check out the specific pages in this guide that apply to you):

• Congenital Dermoid Cysts: These are typically found in infants or children on the head, face, neck, or spine ^[3][4]. They are inclusion cysts, meaning they are “trapped” pockets of skin tissue ^[5].
• Ovarian Dermoid Cysts: Also known as mature cystic teratomas, these occur in the ovaries, most commonly in adolescents and people of reproductive age ^[1]. They are a type of germ-cell tumor ^[6] (meaning they originate from reproductive cells, not that they are a malignant cancer).

While both can contain similar-looking materials like hair and oils, they form through entirely different biological processes.

How Congenital Dermoids Form

Congenital dermoid cysts are the result of a developmental quirk during early fetal growth. As an embryo grows, different layers of tissue fold and fuse together to form the face, skull, and spine ^[7].

Sometimes, a tiny piece of the outer layer (the ectoderm, which eventually becomes skin) gets pinched off and trapped underneath the surface along these fusion lines ^[8]. Because this trapped tissue is genetically programmed to be skin, it continues to behave like skin. It grows, sheds dead skin cells (keratin), and produces skin oils (sebum), which eventually fill the pocket and create a visible lump ^[9][5]. Common locations include the corner of the eyebrow, the bridge of the nose, or the scalp ^[4][10]. A congenital cyst is a natural variation and is not something a parent caused.

How Ovarian Dermoids Form

Ovarian dermoid cysts have a more complex biological origin. They arise from germ cells—the specialized cells in the ovary that are intended to become eggs ^[6].

The prevailing scientific theory is parthenogenesis, a process where a germ cell begins to divide and develop on its own without being fertilized ^[1][11]. Because germ cells are capable of turning into any type of tissue in the human body, they can produce a wide variety of developmental lineages ^[12]. This is why ovarian dermoids are often more “complex” than congenital ones, frequently containing not just skin and hair, but also bone, cartilage, and even fully formed teeth ^[13][9].

What is Inside a Dermoid Cyst?

The contents of these cysts are often the most surprising part of the diagnosis. Because the tissue inside is “mature” (meaning it has fully developed into its final form), it functions just like the tissue on the rest of your body ^[14].

Inside a dermoid cyst, a surgeon may find:

• Sebum: A thick, yellowish, greasy material produced by oil glands ^[9].
• Keratin: Flakes of dead skin cells that often form a “cheesy” or “pearly” white mass ^[15].
• Hair: Strands of hair that grow from follicles within the cyst wall ^[13].
• Teeth and Bone: Most common in ovarian types, these are formed when the germ cells differentiate into skeletal tissue ^[9].
• Fat: Large amounts of mature fat tissue are a hallmark of these cysts and are often what doctors look for on an ultrasound or MRI to confirm the diagnosis ^[11][12].

Understanding the Risks

While the idea of these tissues growing in an unusual place is startling, it is important to remember that they are almost always mature tissues, which means they are generally benign ^[2].

For congenital dermoids, the primary concern is usually their location. If they are near the nose or spine, doctors will check to see if the cyst has a connection to the brain or spinal cord ^[16][17]. For ovarian dermoids, the main risk is torsion—a painful condition where the weight of the cyst causes the ovary to twist, potentially cutting off its blood supply ^[18][19].

While malignant transformation (the cyst turning into cancer) is possible, it is extremely rare, occurring in only about 0.17% to 2% of ovarian cases, usually in older patients ^[20][21]. For the vast majority of patients and parents, a dermoid cyst is a benign occurrence that can be safely managed or removed.