Epidermoid Cancer

What is Epidermoid Cancer?

Epidermoid tumors are a type of tumor that forms at the very start of an embryo’s development. This happens when cells, specifically ectodermal cells, get misplaced during the formation of what’s called the neural tube, a process that takes place during embryogenesis. When this tube closes, some skin cells get trapped and over time, they slowly grow into this tumor.

One thing to note about these tumors is that they are benign, which means they typically aren’t harmful or aggressive. Epidermoid tumors are made solely of ectodermal germ cells. However, there’s another similar type called dermoids, which consist of both ectodermal and mesodermal germ cells.

These tumors go by various names such as central nervous system epidermoid cyst, intracranial epidermoid cyst, and epidermoid brain cyst. The French pathologist Cruveilhier was the first to describe these tumors and he called them the “most beautiful tumors of all the tumors” due to their pearly appearance – hence, they are sometimes referred to as pearly tumors.

What Causes Epidermoid Cancer?

Epidermoid tumors start from skin-like cells that get trapped inside the developing brain tissue when a baby is growing in the womb. This trapping can happen while the brain’s structure is folding. However, some researchers suggest that it could also happen earlier during the development process.

These skin-like cells may get trapped when the brain structure is closing, specifically between the 3rd and 5th weeks of the baby’s development. This usually occurs if the brain tissue doesn’t separate completely from the skin tissue.

In rare cases, an epidermoid tumor can also form if skin cells are accidentally introduced into the brain during a surgery or after a severe brain injury. These are the only instances when epidermoid tumors aren’t linked to how the brain developed before birth.

Risk Factors and Frequency for Epidermoid Cancer

Epidermoid tumors make up between 1% and 2% of all primary brain tumors. These tumors often occur in a region known as the cerebellopontine angle (CPA), found in 40% to 60% of cases, accounting for 4.6% to 6.3% of all CPA lesions. The two most common types of tumors in the CPA are vestibular schwannomas and meningiomas, with epidermoids coming in third. Epidermoids can sometimes be found within the ventricular system, a part of the brain that contains cerebrospinal fluid. It’s quite rare to find these tumors in the brain tissue itself, and they can be mistaken for cystic primary or metastatic tumors.

• Most cases of epidermoids occur between the ages of 30 and 40.
• They are not common in children.
• The ratio of males to females who develop these tumors is 3:2.

Signs and Symptoms of Epidermoid Cancer

A tumor’s location can affect the symptoms a person experiences. Epidermoids in the cerebellopontine angle (CPA), a part of the brain near the cranial nerves, may cause symptoms due to their growth and adhesion to nerves, brainstem, and blood vessels. They can lead to inflammation by accumulating keratin, a type of protein, along the CPA’s cisterns.

• People may have ringing in the ears (tinnitus), headaches, facial twitching, reduced sensation in the face, double vision, facial weakness, facial pain, seizures, vision problems, hearing loss, or balance problems.
• If the CPA tumor compresses the trigeminal or facial nerves, symptoms may resemble those of trigeminal neuralgia (facial pain) or hemifacial spasm (irregular facial muscle movements).
• There can also be an accumulation of cerebrospinal fluid in the brain (hydrocephalus) due to blockage of its outlets.

Rarely, the tumor might leak keratin into the surrounding cisterns, causing a non-infection-related inflammation of the membranes that cover the brain and spinal cord (aseptic or chemical meningitis). This can also occur post-surgery if the keratin and cholesterol breakdown products spill into the subarachnoid space, the area between two of the brain coverings. Meningitis can also lead to hydrocephalus. Using corticosteroids after surgery can reduce the incidence of aseptic meningitis, which can range from 0% to 40%.

Testing for Epidermoid Cancer

Epidermoid brain tumors are a type of brain tumor that can be seen on a CT (computed tomography) scan, but they are more accurately diagnosed with an MRI (Magnetic Resonance Imaging).

On a CT scan, the tumor appears as a same-colored (homogeneous) less dense (hypodense) area with irregular borders, but it doesn’t get brighter with contrast (a special dye given to make certain parts of the body show up better on the scan). However, on the CT scan, it’s hard to tell these tumors apart from a particular type of brain cyst called an arachnoid cyst.

MRI scans show more detailed pictures. An MRI uses two sequences, T1 and T2, where the tumor has the same intensity as the cerebrospinal fluid (CSF – the clear, colorless body fluid found in the brain and spinal cord) but doesn’t get brighter with enhancement. However, other types of MRI scans, known as Fast Fluid-attenuated Inversion Recovery (Fast-FLAIR) or echo-planar diffusion-weighted imaging (DWI), are better at catching these tumors. In a Fast-FLAIR image, the tumor gives off a mix of signals that are higher than the cerebrospinal fluid (CSF). In the DWI, the tumor appears bright compared to the CSF. These tumors often do not cause swelling or show enhancement because they are typically benign (not cancerous) and grow slowly.

Most often, these tumors are found in areas of the brain known as the cerebellopontine angle and the parasellar area. However, they may also be found less frequently in the Sylvian fissure (a deep groove in the brain), the suprasellar region (above the ‘sellar’ region, which is a small area at the base of the brain), or the pineal region, or between the two hemispheres of the brain. Some epidermoid tumors may not look typical on radiology scans. Other tumors might confuse these odd-looking epidermoid tumors. Most of these unusual epidermoid tumors have been found to bleed spontaneously, which could be the cause of their atypical appearance.

Treatment Options for Epidermoid Cancer

The primary aim of managing epidermoid tumors is to completely remove them while ensuring that the function of the nerves in the brain or cranial nerves are preserved. However, in some situations, it is impossible to remove the entire tumor without causing severe effects. In such cases, the majority of the tumor, or ‘subtotal resection’, is removed, which is usually acceptable. During this procedure, doctors use neurophysiological monitoring to prevent damage to the nerves and the brainstem.

The extent of the tumor removal will depend on how strongly the tumor is attached to the surrounding structures and how far it has spread. Tumors which have grown extensively into the supratentorial area (the upper part of the brain) could need a suboccipital approach, which involves performing the operation from the back of the head. These cases may result in not all of the tumor being removed, even when the tentorium, a membrane separating different parts of the brain, is opened.

The surgical approach doctors choose depends on where the tumor is located within the brain. Supratentorial tumors are often removed via either the pterional or frontotemporal approach; both procedures involve making an incision on the side of the head. When tumors are located in the mid-part of the brain or ‘mesencephalic area’, surgeons may opt for a supratentorial posterior interhemispheric transtentorial approach or an infratentorial/supracerebellar approach. When tumors are found in the back area of the brain, or ‘posterior fossa’, a medially or laterally positioned suboccipital craniotomy is usually performed.

The retrosigmoid approach can be effective for tumors in the cerebellopontine angle (CPA) area, the space at the lower back part of the brain. The surgical procedure involves carefully separating the tumor from the structures it has affected to prevent the tumor from growing back. Care must be taken to ensure that the contents of the tumor do not spill into the surrounding fluid-filled space of the brain, as they can cause a severe inflammatory reaction, known as aseptic meningitis. Surgeons usually wash the area slowly during the procedure to remove any remnants and prevent the spread of these remnants to other parts of the brain. Sometimes, a special instrument called an endoscope may be used to help ensure that all parts of the tumor are removed.

It’s important to know that these tumors may grow back, as the leftover tissue continues to produce keratin, a type of protein. About 25% of patients experience tumor regrowth, typically around 8 years after the initial surgery. Patients with residual tumors are monitored annually with brain imaging studies, given that these tumors tend to grow back slowly over many years.

If the tumor returns, external beam radiotherapy, a type of radiation treatment, might be recommended. This could be particularly beneficial for patients who have had multiple recurrences, whose disease has recurred quickly after the previous removal, who have a high risk of complications from further surgery and those whose tumors have turned cancerous.

What else can Epidermoid Cancer be?

When it comes to identifying various health conditions, some conditions that can be mistaken for each other include:

• Arachnoid cyst
• Dermoid cyst
• Metastatic tumor
• Chordoma
• Chondrosarcoma
• Slow growing brain tumors
• Rathke cleft cyst
• Abscess

What to expect with Epidermoid Cancer

More than 75% of patients recover exceptionally well after the operation, being able to lead independent and useful lives. It’s also encouraging that the 20-year survival rate is at a high of 92.8%. Some functions of the trigeminal and facial nerves, which play a key role in sensation and movement of the face, may return after decompression. However, it’s uncertain whether the symptoms related to the cochlear nerve, which is responsible for hearing, will subside.

Most remaining tumors don’t require further surgery, as they tend to grow very slowly. As such, doctors usually recommend having annual imaging tests of the brain, like MRIs, to keep an eye on them. However, if the tumor does dangerously change into a malignant state, also known as cancer, the outlook is less than ideal with an average survival duration of around 9 months.

Possible Complications When Diagnosed with Epidermoid Cancer

Possible post-surgery complications include:

• Worsening of existing or new issues with cranial nerves, which are nerves in your head that control how you see, hear, face feelings, taste, and more.
• Aseptic meningitis, which is inflammation of the protective membranes covering the brain and spinal cord and is not caused by bacteria.
• CSF fistulas and leakage, where the fluid that surrounds the brain and spinal cord leaks out.
• Infections.
• Seizures, which are sudden uncontrolled electrical disturbances in the brain.
• Postoperative hematomas, where blood collects outside of the blood vessels after surgery.
• Hydrocephalus, an accumulation of fluid within the brain that causes increased pressure inside the head.
• Postoperative neurological deficits, where there may be a loss of normal brain function after surgery.

Preventing Epidermoid Cancer

It’s important for patients to understand the nature of their tumor. It is present from birth, not harmful, and grows slowly. If the patient doesn’t show any symptoms, doctors often wait and observe the situation over a few years. Sometimes, the patient undergoes treatment for a long time for facial conditions like ‘trigeminal neuralgia’ (a nerve-related facial pain) or ‘hemifacial spasm’ (an involuntary twitching of facial muscles), until a more detailed brain-scanning test is done.

The patient should also know that even though surgery can reduce symptoms, it also carries some risks. To minimize these risks, Doctors prefer what’s called a ‘subtotal resection.’ This procedure removes part, but not all, of the tumor, while keeping as much normal function as possible. However, a ‘gross total resection’ that removes all the tumor, is avoided if it carries a high chance of causing new effects on the brain or nerves.

When some tumor is left behind after surgery, patients need to commit to long-term check-ups and brain-imaging tests. These are important to keep an eye on the remaining tumor over time.