Not a Monster, Just a Teratoma!

Where do Eggs Come From?

The ovaries are two small organs in the female reproductive system, located on either side of the uterus (Figure 1). Inside the ovaries are special cells called oocytes, also known as eggs. These eggs are very important because they contain genetic information that can be passed from a mother to her baby.

Figure 1 - Illustration of the female reproductive system (Image credit: https://my.clevelandclinic.org/health/body/22999-ovaries).

Long before a baby girl is born, while she still is growing inside her mother’s uterus, her body creates all the eggs she will ever have. It all begins with special starter cells that have the potential to become any type of tissue in the body. These starter cells, called primordial germ cells (PGCs), travel to the ovaries before turning into egg cells [1]. The egg cells then copy themselves to make many eggs; this process is called mitosis. The eggs then go through a special mixing process called meiosis, so each egg becomes unique. After this, the egg falls into a “sleeping” state until puberty. After puberty, one egg wakes up each month and finishes developing so it can be ready for fertilization.

How Can a Tumor Grow Teeth?

An ovarian teratoma is a common growth that can either appear in the body at birth or develop during adulthood. These tumors are unique in appearance as they can grow teeth, hair, and even bone. Their name comes from the Greek word “teras”, which translates to monster [2]!

For many years, people believed strange ideas about where teratomas came from, including witchcraft, eating bones and hair, and other supernatural causes [3]. Today, scientists know these ideas are not true, but the exact cause of teratomas is still being researched.

What we do know is that teratomas can contain many different types of tissues, which explains their weird appearance. This is because teratomas are made from cells that come from all three germ layers: the ectoderm, mesoderm, and endoderm. These germ layers are like the building blocks for our bodies. The ectoderm makes skin and hair, the mesoderm makes bones and muscles, and the endoderm makes organs like the lungs and stomach [1].

There are two main theories that help explain why teratomas happen. The first is called the parthenogenetic activation theory. This theory suggests that teratomas come from a mature egg cell that starts developing on its own without being fertilized [3]. It doubles its own DNA and acts like an embryo, meaning it can grow any tissue type in the body. The second theory is called the primitive germ cell migration theory. This theory suggests that teratomas come from PGCs that never properly developed into egg cells in the ovaries, meaning they kept their ability to turn into many tissue types [4].

Both theories explain why teratomas can contain many different tissue types, as the cells involved still have the potential to develop into many body parts.

Types of Teratomas

There are three main types of teratomas. The first type of teratomas are called mature teratomas (Figure 2). These are the most common type and are usually found in young women during their reproductive years [5]. They are non-cancerous and usually do not cause any symptoms, but larger ones might cause abdominal pain, bloating, or frequent urination [3]. These teratomas contain tissues from all three germ layers. The second type of teratomas are called monodermal teratomas. These are a rare type of teratoma made up of thyroid tissue, which comes from the endoderm. Women who get this type of teratoma have symptoms of hyperthyroidism, which include weight loss, sweating, and a fast heart rate [3]. The third type of teratomas are called immature teratomas. These are extremely rare and cancerous teratomas. They usually affect teenagers and young women [3]. Symptoms usually include abdominal pain and loss of periods.

Figure 2 - A mature ovarian teratoma (Image credit: https://radiopaedia.org/cases/mature-cystic-ovarian-teratoma-gross-pathology-1).

How Doctors Handle Teratomas

In most cases, teratomas are not dangerous, and doctors keep a close eye on them to ensure they do not cause any problems. However, if needed, there are multiple safe and effective ways to treat a teratoma. Treatment depends on multiple factors such as the teratoma’s size, the patient’s symptoms, and whether the teratoma is cancerous. If the teratoma is small and is not causing any issues, the doctor may choose to monitor it over time. If the teratoma is larger, growing at a rapid rate, or causing symptoms, surgery is the best option for treatment.

There are many surgical options depending on the characteristics of the teratoma. Overall, laparoscopic surgery is the best option for removing a teratoma. Laparoscopy uses special instruments, including a tiny camera, that are introduced through small incisions made on the abdominal wall (Figure 3). Laparoscopic surgery is much easier on the patient than traditional surgery in which the surgeon must make a large incision. The teratoma can be removed directly from the ovaries using this equipment. However, if the teratoma involves the entire ovary and has altered its structure, removing the entire ovary in a laparoscopic procedure called an oophorectomy is recommended. Finally, in rare cases in which the teratoma is cancerous, regular surgical removal and chemotherapy treatment may be required [3]. The good news is that there are multiple safe options for treating teratomas, and with the growing amount of research on this topic, more safe methods will continue to be discovered for years to come.

Figure 3 - A laparoscopic surgery (Image credit: https://my.clevelandclinic.org/health/procedures/4819-laparoscopy).

More to Discover

Although teratomas may seem frightening upon first glance, when we dig a little deeper into the science behind them, it becomes clear that they are simply a natural, although unusual, phenomenon. People have come a long way from believing that teratomas stemmed from supernatural beings like witches and the devil. Medical research has gained a better understanding of how they start and how to effectively treat them. What still remains a mystery is the exact cause behind them and why they occur in some people and not others. What causes some cells to take the wrong path while others stick to the rules? Perhaps a reader like you will be able to solve this question one day and contribute to the rapidly evolving knowledge of the human body.

Glossary

Uterus: ↑ The muscular organ of a female mammal in which the young develop before birth.

Primordial Germ Cells: ↑ Special cells in a baby’s body that are the first cells that can grow into eggs (in girls) or sperm (in boys) later in life.

Puberty: ↑ The stage when a child’s body changes into an adult body, driven by hormones. It includes growth of sex organs, body hair or breasts, and, in girls, the first menstrual period.

Ovarian Teratoma: ↑ A type of lump that can grow in the ovaries, arising from special early cells and can contain different kinds of body tissues like hair, skin or teeth.

Germ Layers: ↑ The three early layers of cells in a developing baby that grow to form all the different parts of the body.

Hyperthyroidism: ↑ Abnormally high activity of the thyroid gland.

Laparoscopic Surgery: ↑ A type of surgery where doctors fix a problem inside of the body using tiny cutes and a small camera instead of making a big opening.

Oophorectomy: ↑ A surgery where a doctor removed one or both ovaries from the body.

Conflict of Interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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[1] ↑ Langman, J. 1995. Langman’s Medical Embryology. Baltimore, MD: Williams & Wilkins, 486. Available online at: http://archive.org/details/langmansmedicale0000lang (Accessed August 5, 2025).

[2] ↑ Ahmed, A., and Lotfollahzadeh, S. 2025. “Cystic teratoma,” in StatPearls (Treasure Island, FL: StatPearls Publishing). Available online at: http://www.ncbi.nlm.nih.gov/books/NBK564325/ (Accessed August 5, 2025).

[3] ↑ Kumar, V., Abbas, A. K., Fausto, N., and Aster, J. C. 2009. Robbins and Cotran Pathologic Basis of Disease, 8th edn. Philadelphia, PN: Saunders/Elsevier.

[4] ↑ Salzillo, C., Imparato, A., Fortarezza, F., Maniglio, S., Lucà, S., La Verde, M., et al. 2024. Gonadal Teratomas: a state-of-the-art review in pathology. Cancers 16:2412. doi: 10.3390/cancers16132412

[5] ↑ Cong, L., Wang, S., Yeung, S. Y., Lee, J. H. S., Chung, J. P. W., and Chan, D. Y. L. 2023 Mature cystic teratoma: an integrated review. Int. J. Mol. Sci. 24:6141. doi: 10.3390/ijms24076141