Dermoids & epidermoids

Dermoid cysts and epidermoid cysts are benign, congenital tumors. They usually present as very slow-growing, painless cysts. They can occur in the skull, the scalp, the brain, and the spinal canal.

How common are dermoids and epidermoids and where do they occur?

Dermoid and epidermoid tumors are very rare and account for only 0.3–1% of all brain tumors. Epidermoid tumors are slightly more common overall and usually develop in the brain at the cerebellopontine angle, a space between the cerebellum and the brainstem. Dermoid tumors, on the other hand, tend to occur along the midline, for example near the pituitary gland.

How do dermoid and epidermoid cysts form?

Dermoid and epidermoid cysts result from a malformation of embryonic tissue in which skin cells become trapped within the neural tube during embryonic development. While epidermoid cysts develop from scattered skin epithelium, dermoid cysts can additionally contain other skin components such as hair, glands, or even tooth buds.

These cells undergo the same renewal processes as normal skin cells. The resulting material accumulates inside the cyst, leading to slow, steady growth. Dermoid and epidermoid cysts therefore typically exhibit linear growth.

What are the symptoms of dermoids and epidermoids?

Because of their slow growth, epidermoid cysts usually become noticeable only between the ages of 25 and 50 due to new symptoms, whereas dermoid cysts are more commonly detected during childhood. Symptoms arise once the tumor reaches a certain size due to local pressure on surrounding structures and can vary greatly depending on the location:

  • If the tumor is located in the cerebellopontine angle, it typically causes cranial nerve deficits.
  • If the tumor grows near the pituitary gland, hormonal imbalances may occur.
  • In the spinal canal, dermoid and epidermoid cysts can cause pain and/or sensorimotor deficits by compressing the spinal cord or nerve roots.
  • If the cyst contents drain, aseptic (germ-free) meningitis may occur, accompanied by fever, headache, and neck stiffness. If this occurs repeatedly, it is also referred to as Mollaret meningitis.
  • Occasionally, dermoid cysts with fistula formation can lead to a bacterial infection. This is most commonly caused by the skin bacterium Staphylococcus aureus.
  • In addition, skin changes with altered hair growth or pigmentation may occur.

How are dermoids and epidermoids diagnosed?

On computed tomography (CT) scans, epidermoid and dermoid cysts appear as sharply defined lesions that do not take up contrast. On magnetic resonance imaging (MRI), epidermoid cysts can be mistaken for arachnoid cysts due to similar signal characteristics. Special diffusion-weighted MRI sequences can be helpful for differentiation, as epidermoid cysts appear bright in contrast to the cerebrospinal fluid in arachnoid cysts. Dermoid cysts are recognizable by characteristic signal patterns due to their fat content. However, a definitive diagnosis is only possible after histological examination of the tissue.

How are dermoids and epidermoids treated?

Treatment depends on the location, size, growth rate, and symptoms. For symptomatic or rapidly growing dermoid and epidermoid cysts, microsurgical resection is the treatment of choice. The goal is to remove as much of the cyst contents and cyst wall as possible while preserving neurological function.

Since epidermoid cysts in particular can be closely attached to cranial nerves, blood vessels, the brainstem, or the spinal cord, the cyst wall is not removed at any cost. Remaining tumor debris may regrow over time, which is why regular MRI follow-ups are recommended. Complete resection significantly reduces the risk of recurrence.

Postoperative radiation therapy is generally not indicated for benign dermoid and epidermoid cysts. In cases of repeated recurrences or high surgical risk, it may be discussed on an interdisciplinary basis for epidermoid cysts in individual cases; however, it does not constitute standard therapy.

Malignant transformation of epidermoid cysts into squamous cell carcinomas is very rare. Indications of this may include rapid growth, new contrast uptake on MRI, or rapid clinical deterioration.

Why you should seek treatment at Inselspital

At Inselspital, we are constantly striving to find the best possible individualized treatment strategy for our patients. We achieve this through close interdisciplinary collaboration at our certified brain tumor center.

At weekly tumor board meetings, specialists from neurosurgery, neurology, neuro-oncology, nuclear medicine, radiation oncology, and pathology discuss each patient individually to determine the optimal treatment.

For surgical treatment, we use innovative technical procedures such as neuronavigation and intraoperative neuromonitoring. These ensure maximum precision and the highest level of safety for our patients.

Further reading