Dermoids & epidermoids

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Dermoids (also dermal cysts or dermoid cysts) and epidermoids (also epidermal cysts or epidermoid cysts) are benign, congenital tumors. They usually present as very slow-growing and painless cysts. They can occur in the skull bone, scalp, brain, but also in the spinal canal of the spine.

Clinical importance

Dermoids and epidermoids are very rare tumors. They account for only 0.3-1% of all brain tumors. Epidermoids are slightly more common than dermoids and grow most frequently in the brain at the cerebellopontine angle. Dermoids, on the other hand, occur preferentially in the midline, for example, near the pituitary gland.

In contrast to new tumors with exponential growth, dermoids and epidermoids exhibit linear growth. They are usually first noticed between the ages of 25 and 50, although dermoids are more common in younger patients.

What are the causes of dermoids and epidermoids?

Originally, dermoids and epidermoids are a maldevelopment of embryonic tissue. Embryonic skin cells were scattered into the neural tube during embryonic development and trapped there. Epidermoids arise only from scattered epithelial cells of the skin, whereas dermoids also contain all other skin layers including skin appendages such as hairs, glands or even dental systems. These scattered cells are subject to the same cycle as our skin. The skin cells and skin appendages are accumulated inside the cyst, leading to slow and steady growth.

What are the symptoms of dermoids and epidermoids?

Because they grow very slowly, dermoids and epidermoids become noticeable only late. When they have reached a certain size, they can spread to the surrounding healthy brain tissue, displace it locally and cause corresponding symptoms. These are very diverse and depend on the localization and size of the tumors.

  • If the mass is located in the cerebellopontine angle, patients typically suffer from cranial nerve deficits.
  • If the growth is near the pituitary gland, hormonal imbalances may occur.
  • In the spinal canal, dermoids and epidermoids with space-occupying effects on the spinal cord or nerve roots can lead to pain or sensorimotor deficits.
  • Spontaneous evacuation of the capsular contents may also result in aseptic meningitis with fever, headache, and neck stiffness. This is also known as Mollaret's meningitis. 
  • Occasionally, dermoids with fistula formation may develop a bacterial superinfection. Most commonly, this is caused by the skin germ Staphylococcus aureus.
  • Other symptoms caused by the fistula (connection to the skin surface) include skin changes with altered hair growth or pigmentation.

How are dermoids and epidermoids diagnosed?

On radiographs and computed tomography (CT) images, epidermoids and dermoids appear as sharply demarcated, round lesions without contrast. On magnetic resonance imaging (MRI), the signal intensity of epidermoids resembles that of cerebrospinal fluid (CSF), which is why they can be confused with arachnoid cysts, among others. The diffusion-weighted MRI sequence, in which epidermoids appear bright in contrast to CSF, can be helpful in distinguishing them. However, a definitive diagnosis is only possible after histological examination of the tissue.

How are dermoids and epidermoids treated?

The therapy of choice is microsurgical resection of the dermoids and epidermoids including the cyst wall. Depending on the localization, it may be necessary to leave the capsule at the border to important structures such as cranial nerves or the pituitary stalk in order not to damage them. Such cysts may increase in size again in the course of time, so that a new resection becomes necessary.

Recurrence rates of up to 26% are reported in the literature. However, with complete removal patients are usually cured. Since dermoids and epidermoids are benign tumors, there is no need for follow-up radiation. Tumor recurrence cannot be prevented by radiation. In very rare cases, however, transformation from a benign epidermoid to a malignant squamous cell carcinoma may occur.

Why you should seek treatment at Inselspital

At Inselspital, the best possible treatment strategy is determined individually for each patient. This is done in the certified neuro-oncological tumor center by an interdisciplinary team. This so-called tumor board, which meets weekly, is composed of specialists from neurosurgery, neurology, neuro-oncology, nuclear medicine, radio-oncology and pathology. Here, each patient is discussed individually in order to determine the optimal treatment options.

For the operation itself, we use innovative technical procedures such as neuronavigation and so-called intraoperative neuromonitoring. These new achievements are a guarantee for maximum precision during surgery and maximum safety for our patients.

Further reading