Pilar cyst: Causes, risk factors, identification, diagnosis, treatment and images

Pilar cyst: Causes, risk factors, identification, diagnosis, treatment and images
Pilar cyst: Causes, risk factors, identification, diagnosis, treatment and images

What are pilar cysts?

Pilar cysts, also known as trichilemmal cysts or wens, are small elevations that appear on the surface of the skin. These cysts are often flesh coloured. They are benign cysts. This means that they are not cancerous. Therefore these cysts are not a cause for concern, but they can be really uncomfortable. These cysts form from a hair follicle and therefore is most often seen on the scalp.

Pilar cysts are filled with a protein called Keratin. Keratin is the protein that is involved in making up your hair and nails.

It has also come to notice that pilar cysts usually appear more frequently in the middle aged females. They alo have an autosomal pattern of inheritance and therefore runs in families.

Nearly 2% of all trichilemmal cysts, proliferate to form tumours known as proliferating trichilemmal cysts. These proliferating trichilemmal cysts enlarge over time upto about 25 cm in its diameter and they often ulcerate.  Although these cysts are known to be benign biologically, they are locally aggressive. There have been a few instances where these cyst underwent a malignant transformation and has led to recurrences and metastases.

What does a pilar cyst look like?

As mentioned earlier, the pilar cysts have the same colour as your skin. They are round elevated lesions that arise from a hair follicle. They do not contain pus and typically not painful to touch.

Pilar cysts arise from hair follicles and therefore they are most commonly seen in the scalp. Although scalp is the most common place for these cysts to occur, they can occur anywhere on the body. Other possible sites, where these cysts can occur are your face and neck. Most people will have more than one pilar cyst.

The size of these cysts varies in size. While some may be small as the size of a quarter, the other can grow to the size of a small ball. The growth of these pilar cysts is gradual and occurs slowly over time.  On palpation of these lesions, they are usually firm in consistency and have a smooth surface. They do not contain pus and are usually not painful to touch.

These cysts are not harmful and usually develop without causing any problems in the patient. However, there is a possibility for this cyst to rupture following trauma and sometimes even on its own. Once it ruptures, a rash may appear, and there can be associated pain or irritation in the affected area.

Infection of this pilar cyst is a possibility, even though it is not very common. If the cyst gets infected, you may develop pain and there can be associated oozing from the site of the cyst. Infection is most likely possible if you have ruptured your pilar cyst or if an incision was made on it.

The appearance of pilar cysts may look like a sebaceous cyst and therefore are commonly mistaken as sebaceous cyst. However, the point in which you can differentiate a sebaceous cyst from a pilar cyst is that sebaceous cysts often have a central punctum, whereas a pilar cyst does not have such a punctum. Also, pilar cysts can be painful and inflamed.

pilar cyst pictures scalp

What is a sebaceous cyst?

Sebaceous cysts are common cysts that mainly arise in the face, neck and the trunk. These cysts are not a danger as they are non-cancerous but they can be uncomfortable if you leave them be. Sebaceous cysts often do not need any investigations to be diagnosed; instead they are diagnosed by history and physical examination.

Sebaceous cysts form within the sebaceous glands. The sebaceous glands are glands that are found on your skin and are responsible for the production of oil called as sebum. Sebum coats your hair and skin. Cysts can arise from these glands and they are named as sebaceous glands. These cysts typically arise when either the duct through which the oil leaves the gland or the gland itself is blocked or damaged. Sebaceous glands normally occur if there is any trauma to that particular area of the body. Trauma can be any form such as a simple scratch, a wound or a particular skin condition such as acne.

What is the difference between a pilar cyst and a sebaceous cyst?
What is the difference between a pilar cyst and a sebaceous cyst?

The growth of sebaceous glands is very slow and therefore the trauma would have happened either months or weeks before you notice the cyst.

Trauma is just one cause of sebaceous cysts. Other causes of sebaceous cysts include:

  1. If there is something wrong with the duct like a deformity
  2. If there is damage to the cells
  3. Certain genetic conditions such as basal cell nevus syndrome.

Symptoms of sebaceous cyst

You may notice a lump on your body, especially on the scalp, face, neck and the back. These cysts are typically not painful. However, as they grow larger, they can become uncomfortable and sometimes painful.

Treatment of sebaceous cyst

The treatment of a sebaceous cyst is either by draining the cyst or by surgically removing the cyst. The usual method of treatment for a sebaceous cyst is by removing it. This choice is taken not because sebaceous cysts are dangerous but because most people are concerned about the cosmetic aspect of having such a cyst in their body. Since having a sebaceous cyst is not something dangerous, your health care provider will allow you to pick which method of treatment you would prefer.

When deciding which method to go for, it is important to remember that if you do not remove a sebaceous cyst surgically, there is a chance that the cyst can come back again. Therefore the best treatment is to surgically remove the cyst. However, a few patients prefer to go for a drainage of the cyst because surgical removal can cause scarring.

The following methods may be utilised by your surgeon to remove the sebaceous cyst:

  1. Wide excision – In this method, your surgeon will make a long incision to completely remove the cyst. However, it can leave a long scar.
  2. Minimal excision – This method leaves a minimal scar but there is a risk of getting the sebaceous cyst back.
  3. Laser with punch biopsy incision – A laser is used to punch a hole on the cyst to drain it and then about one month later, the outer walls of the cyst will be removed.

Once the cyst is removed, antibiotics will be given to prevent the development of an infection

Pilar Cysts : Causes, Pictures, Symptoms and Treatment

How common is Pilar or trichilemmal cysts?

In the United States, pilar cysts occur in 5 – 10% of the population. There seems to have no known racial preference. When talking about sex wise, trichilemmal cysts seem to be more common in women than men and the most common age group that is affected by pilar cysts is the middle aged persons than that younger age group.

How are Pilar cysts diagnosed?

Pilar cysts can be diagnosed by yourself even at home, if you know to identify the characteristic features of a pilar cyst. However, it is important that you consult your health care provider or a dermatologist to confirm your diagnosis. They can confirm the diagnosis and fins out the underlying cause that may have caused this cyst to arise, especially the causes that are more serious.

To confirm your diagnosis, your doctor will do a biopsy. A biopsy is a small procedure where a tiny sample is taken from the lesion and this will be viewed under the microscope to identify characteristic features that may be consistent with a diagnosis of pilar cyst. If these features are present, then a diagnosis of pilar cyst can be made.

A cyst may be biopsied especially when it ruptures and gets inflamed. These cysts should then be excised and sent for histopathology. This is done to exclude serious conditions such as cancers. Two of the most important cancers that should be excluded are a nodular or nodulocystic basal cell carcinoma.

What features are expected to be seen under a microscope in a trichilemmal cyst?

These cysts are usually surrounded by a fibrous capsule and against this are several cells which are small, cuboidal and darkly stained epithelial cells. There will be no distinct intercellular bridging in between these cells. These cells bind with squamous epithelial cells that are made up of swollen keratinocytes. These cells in increase in their height as they mature and transforms into solid. The point of differentiation of a trichilemmal cyst from an epidermoid cyst is that in an epidermoid cyst, there is a granular cell layer that lines the epithelium.

Both trichilemmal cysts and epidermoid cells have keratin. However, the keratin in pilar cysts stain keratin with antikeratin antibodies which is usually found in human hair while on the other hand, epidermal cyst keratin stains with antikeratin antibodies that are derived from human callus.

Your health care provider may also order further investigations such as a CT scan as needed. A CT scan is usually ordered to rule out the possibility of a cancer and other types of cysts.

Other radiographic scans in addition to a CT scan such as MRI scan of the head may also be necessary to differentiate other midline scalp lesions that may be a connected to the meninges of your CNS (central nervous system).

How is a pilar cyst treated and managed?

Management of a pilar cyst includes both medical and surgical treatment.

Medical treatment

If you are experiencing pain, swelling and redness or even a purulent discharge from the cyst, you may need treatment. These are signs of an infection and you will require treatment with antibiotics. Before the commencement of antibiotic treatment, a wound culture will be taken.

Other than that there are no topical or systemic drugs available to treat pilar cysts or trichilemmal cysts.

Surgical treatment

This is the most definitive treatment for a pilar cyst. Surgical management of a pilar cyst is by surgical excision. There are several methods that can be utilised to get rid of the cyst. First, a small linear incision is made over the cyst and the lesion is excised.

For the procedure of excision of a pilar cyst, the following steps may be followed:

  1. First the area of the lesion should be anesthetized. A local anesthetic is preferably used. An injection will be given around the lesion to make that area numb so that you will not feel anything when the incision is made. However, when this injection is given you may feel a small sting for a fraction of a second and then it will go away.
  2. Next, a small incision is made over the centre of the cyst. This incision may be either a linear, elliptical or a punch incision. An elliptical incision is the best option as this allows the surgeon to gain access to all corners of the lesion and allow better clearance. The incision is usually made using a dermal punch biopsy tool.
  3. As mentioned earlier, the pilar cysts are surrounded by a thick fibrous capsule and due to this thickness; the entire cyst can be excised without damaging the cyst wall and expressing its contents. However, there have been numerous instances where the cyst wall is ruptured and the contents expressed. In such cases, a curette is used to dislodge the outer wall of the cyst from the surrounding tissue.
  4. While holding on to the edge of the cyst with the help of forceps, the cyst wall should be separated from the surrounding connective tissue by making a blunt dissection.
  5. Bleeding should be expected as with any incisional procedure and therefore controlling the bleeding and achieving haemostasis is extremely important. Once this is done, the wound should be dressed properly.

If you have a ruptured or an infected pilar cyst, then you should avoid excision of this cyst until the inflammation has reduced. This is extremely important to reduce the chance of the infection spreading to other areas of the body and wound healing problems.

Most of the pilar cysts are completely cured with the excision of the cyst completely. There are certain instances where additional treatment strategies such as radiotherapy and chemotherapy are considered, especially when there are multiple pilar cysts on the body which needs surgical excision.

What are the complications that can arise?

The most common complications associated with pilar cyst or trichilemmal cysts are:

  1. Infection of the cyst
  2. Rupture of the cyst – This can follow trauma to the cyst and traumatization can occur while combing or brushing your hair.
  3. Proliferation of the cyst eventually leading to ulceration

Another complication that is associated with pilar or trichilemmal cysts include the ability for a malignant transformation. This change is extremely rare but it still can occur.

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Thilini Gunawardane
About Thilini Gunawardane 28 Articles
I am a final year medical student and I'm currently doing my clinical rotations in a private hospital. A huge people-person, an open minded who spent several years in the field of Medicine. I am at my final year on Medicine and clinical rotations at a Hospital (Dr Neville Fernando Teaching Hospital (NFTH). My long term run is to be a consultant one day and serve everyone in need. This has always been in my bucket list and I myself as a go-getter, will make my promisses and prove it to my self. Every-day I wake up knowing how little I know and I work for it. I learn, I use all my sources I have. Working online, I have gained so much experience and learned many things that a person should have in a working environment, time/project management, satisfying the client, meeting deadlines on time.

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