Sebaceous cyst – the skin is lubricated by sebaceous fluid. This fluid can build up inside a pore or hair follicle and form a hard lump filled with thick, greasy matter. When squeezed, a small dome-shaped projection will appear (the punctum), representing the opening of the cyst. This may allow material to be expressed (squeezed out). Treatment includes drugs, draining the cyst with a small needle, or removal by surgery. Sebaceous cysts are common on the face, back, scalp and scrotum.

Introduction

Epidermoid cyst, also known as a sebaceous cyst, is a benign encapsulated, subepidermal nodule filled with keratin material.  Although most commonly located on the face, neck, and trunk, epidermoid cysts can be found anywhere including the scrotum, genitalia, fingers, and cases within the buccal mucosa. Cysts may progress slowly and remain present for years. The term sebaceous cyst is commonly used; however, the term is a misnomer in that it does not involve the sebaceous gland. Epidermoid cysts develop within the infundibulum. Other common synonyms include infundibular cyst, epidermal cyst, and epidermal inclusion cyst. Although these cysts are recognized as benign lesions, rare malignancy can arise.

Etiology

The majority of cases are of epidermoid cysts are sporadic. Although epidermoid cysts can be found in autosomal dominant (AD) Gardner syndrome (familial adenomatous polyposis) and Gorlin syndrome (basal cell nevus syndrome). Epidermoid cysts occurring before puberty in unusual locations and numbers raise the suspicion of a syndrome. In Favre-Racouchot syndrome (nodular elastosis with cysts and comedones) in elderly patients, epidermoid cysts may result from chronic sun damage. Patients on BRAF inhibitors can develop epidermoid cysts of the face. Lately, imiquimod and cyclosporine have been noted to cause epidermal inclusion cysts.

Epidemiology

Epidermoid cysts are the most common cutaneous cysts and typically occur in the third and fourth decades of life. It is rare to find these cysts before puberty. They are predominantly found in males versus females (ratio 2:1). In the neonatal period, small epidermal cysts, referred to as milia, are common. Approximately 1% of epidermoid cysts have been noted to have a malignant transformation to squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).

Pathophysiology

Epidermoid cysts are derived from the follicular infundibulum. Generally, these cysts are the result of plugging of the follicular orifice. The cyst communicates with the surface of the skin through a keratin-filled orifice. Disruption of the follicle is important in the pathogenesis as those with acne vulgaris may have multiple epidermoid cysts originating from comedones. Additionally, they can also occur from traumatic and penetrate injuring leading to the implantation of the epithelium. Epidermoid cysts are lined with stratified squamous epithelium that leads to an accumulation of keratin within the subepidermal layer or dermis. Generally, the cysts are asymptomatic until they rupture. When the cysts rupture, an inflammatory reaction occurs from the displacement of soft and yellow keratin into the dermis and surrounding tissue. Recently ultraviolet (UV) light and infection with the human papillomavirus (HPV) have been implicated as causing epidermoid cysts.

Histopathology

Stratified squamous epithelium lines the cyst. Histological examination reveals an epithelial-lined cyst filled with laminated keratin located within the dermis. The lining of the cyst is similar to the surface epithelium but differs in that it lacks rete ridges.  A granular layer is present that is filled with keratohyalin granules.

History and Physical

Physical examination generally reveals a 0.5 cm to several centimeters of non-fluctuant, compressible mass. A central, dark comedone opening (punctum) is often described. Epidermoid cysts are usually asymptomatic; however, if ruptured it may closely resemble a furuncle with tenderness to palpation, erythema, and swelling. A foul-smelling yellowish cheese-like material discharged from the skin may be described. Some patients may describe an event of a fall on their back or someone slapping their back causing painful swelling and the resulting cystic rupture. Epidermoid cysts can be found anywhere but are commonly found on the face, neck, chest, upper back, scrotum, and genitals. They can also be found on the buttocks, palms, and plantar side of feet if due to penetrating trauma. If occurring on the distal portion of the fingers, changes to the nail plate may occur. Taking a good history can aid in determining if the cyst is an isolated case, caused by medications, or if it is part of a genetic syndrome.

Evaluation

Evaluation of epidermoid cysts is based largely upon history and physical. The need for histological examination of the excised mass is often debated. Laboratory examination is not necessary. Radiographic tests are not commonly utilized in the evaluation of epidermoid cysts.

Treatment / Management

The most effective treatment involves complete surgical excision of the cyst with the cyst wall intact. The complete excision should be delayed if an active infection is present as the planes of dissection will be difficult. In these cases an initial incision and drainage may be indicated with a potential for reoccurrence in the future A local anesthetic with epinephrine is preferred to minimize bleeding. The anesthetic should be injected around the cyst, with avoidance of direct injection into the cyst. A small diameter elliptical incision with the inclusion of the central core, or punctum can be utilized. For optimal cosmetic results, maintaining the incision in the minimal skin tension lines is important. A multiple-layered subcuticular and epidermal closure will yield an optimal outcome. An alternative surgical approach can also be done with a punch biopsy and expulsion of the intact cyst through the small defect or standard excision. If there is surrounding inflammation, intralesional triamcinolone may be used to help decrease inflammation in addition to a delay in surgical removal. If the cyst has ruptured and the lining destroyed, the cyst will not reoccur. However, removing of the entire cystic lining is important in decreasing recurrence.

Differential Diagnosis

Depending on location, the differential diagnoses of epidermoid cysts include the following: lipoma, dermoid cyst, pilar cyst (isthmus-catagen cyst, trichilemmal, wen), furuncle, branchial cleft cyst, milia, pilonidal cyst, calcinosis cutis, Pachyonychia Congenita, steatocystoma, and cutaneous findings of Gardner syndrome.

Prognosis

Epidermal inclusion cysts are recognized as benign cysts. However, rare malignancy can occur. Squamous cell carcinoma (SCC) is the most common malignancy followed by basal cell carcinoma (BCC).  In developing malignancy, squamous cell carcinoma occurs approximately 70% of the time.

Complications

Complications of rupture include erythema, swelling, and pain. Complications of surgical removal include bleeding, infection, and scaring. Erythema and pain can be managed with intralesional triamcinolone. Infection following surgery can be prevented using proper aseptic techniques. While recognized as a benign cyst, rare malignancy may occur.

Postoperative and Rehabilitation Care

Following surgical excision, it appropriate to avoid contact sports and strenuous activity. Sutures may be removed within 7-10 days. Patients should be instructed on the fact that the surgical scar will generally take 8 weeks to reach a maximum of 80% tensile strength of the original skin strength. Scar revision, if necessary, should take place between 6 months to 1 year following excision as the remodeling phase of wound healing occurs between 3 weeks to 1 year.

Consultations

Consultations are not necessary unless the cyst is large and in an unusual location such as the mouth or face. In those circumstances, specialist consultation may be warranted. Adults with epidermoid cysts in rare locations such as the fingers and toes, history of multiple lipomas, and a family history of colon cancer should raise the suspicion of Gardner syndrome with an appropriate specialist referral.

Pearls and Other Issues

Epidermoid cysts (sebaceous cysts) are common benign encapsulated cysts. Due to the inflammatory reaction from the release of keratin contents, many practitioners will mistake the cyst for an abscess and prescribe antibiotics.

Enhancing Healthcare Team Outcomes

Epidermal cysts are commonly encountered by the primary care provider, dermatologist, nurse practitioner, surgeon and the internist. While the majority of these cysts are benign, it is important to send the excised sample for evaluation to ensure that there is no malignancy. 

When completely excised, the outcomes are excellent. However, recurrences are common in patients with genetic syndromes.

Introduction

Pilar or Trichilemmal cysts are common dermal cysts. They occur in less than 10% of the population. Of all skin cysts, Pilar cysts are the most common cysts, mostly affect the skin of the scalp. Trichilemmal cysts never give rise to malignant lesions. They are usually sporadic. The cysts contain keratin and are outlined by stratified squamous epithelium similar to what we see in the outer(external) root sheath of the hair follicle. Proliferating trichilemmal cysts are the tumor form of pilar cysts, and it would appear in less than 3% of all cases of pilar cysts, and it might ulcerate and may be locally aggressive.

Etiology

Trichilemmal cysts may be inherited as an autosomal dominant trait. Patients with familial pilar cysts are often younger and often present with multiple lesions at the same time. They arise from the epithelium located between the sebaceous gland and the arrector pili muscle. They are most common on the head especially the scalp. The pilar cyst rate of growth is very slow; it takes several years to grow to a big size.

Epidemiology

Young individuals are more prone to developing trichilemmal cysts. Pilar cysts have no known racial predilection, and they occur more commonly in women than in men. Family history may be present since the disease follows autosomal dominant inheritance in some cases.

Pathophysiology

Pilar cysts are intradermal cysts that arise from the epithelium located between the sebaceous gland and the arrector pili muscle. They are lined by stratified squamous epithelium without a granular cell layer similar to what is seen in the outer root sheath of the hair follicle and filled with keratin and its breakdown products.

Histopathology

Pilar cysts are lined by thick capsules containing small layers of cuboidal, dark-staining basal epithelial cells in a palisade arrangement without an obvious intercellular gap. Those cells coalesce with multiple layers of keratinocytes forming squamous epithelium; these cells showed more maturation with dense eosinophilic-staining keratin in the absence of a granular cell layer. Sometimes we might see some areas of calcifications. Keratin in the pilar cysts stains with antikeratin antibodies similar to that seen in keratin derived from human hair. Trichilemmal cysts might rupture and of their components will leak into the dermis leading to the formation of foreign-body reaction. Rare malignant transformation in the form of increase mitotic figure along with cell atypia and necrosis might be seen in cases of proliferating trichilemmal cysts.

History and Physical

Pilar cysts are primarily diagnosed on clinical presentation. Most commonly, they are multiple lesions, but sometimes, single lesions might be seen. Pilar cysts usually occur in areas with dense hair follicle so that they are most commonly seen on the head especially the scalp, but they can also be found on the face, head, and neck. Trichilemmal cysts are usually asymptomatic unless they calcify or rupture their contents leading to inflammatory process and pain in the affected site. Sometimes, the presence of pilar cyst overpressure or bony prominence might lead to pain. Trichilemmal cysts usually present as flesh-colored, smooth, mobile, firm, and well-circumscribed nodules. Family history is very important since this condition can have an autosomal dominant pattern of inheritance. Usually, they are slow-growing nodules but sometimes they increase in size rapidly and it would indicates infection or malignant transformation. Young females are affected more than males.

Evaluation

Diagnosis of pilar cysts is mainly clinical, based on signs and symptoms and additional investigations rarely need to be done. Radiological studies sometimes are needed to exclude other differentials, especially with midline head and neck lesions and to check for the extent of the lesion and the involvement of the underlying central nervous system (CNS). CT scan is the best way to determine the extent of bone invasion. MRI can be used for more deeper soft tissue involvement and to visualize very tiny invasion.

Treatment / Management

The mainstay of treatment is radical surgical excision of the lesion including the wall of the cysts to avoid the recurrence. Then the content should be sent to the pathology department to confirm the diagnosis. Treatment is complete excision of the cyst. If the cysts return or become inflamed, then it is not recommended to remove surgically, and it is better to wait until the inflammation subsides to proceed to the option of surgical removal. Wound swab and culture sensitivity for the inflamed lesion is mandatory to exclude infection and to guide treatment options. Proliferating trichilemmal cysts might need multiple surgical removal sessions along with radiation therapy and/ or chemotherapy.

Differential Diagnosis

• Acne keloidalis nuchae

• Cutaneous lipomas

• Dermoid cyst

• Epidermal inclusion cyst

• Favre-Racouchot syndrome (nodular elastosis with cysts and comedones)

• Pilomatrixoma

• Steatocystoma multiplex

Treatment Planning

1. Conservative treatment

2. Surgical intervention in the form of complete surgical excision of the cyst with its sac to avoid recurrence

3. Radiotherapy for select cases with malignant transformation

4. Chemotherapy for rare malignant cases

Prognosis

Generally, pilar cysts have good prognosis regardless of the presence of complications. Sequelae of trichilemmal cysts include inflammation, infection and malignant transformation (which is rare). Counseling is needed to assure the patient and his or her family since the disease is transmitted through the autosomal dominant way.

Complications

A pilar cyst might cause pain especially over pressure areas; other complications include inflammation, cosmetic disfigurements, infection, and calcification. A complication from surgical removal may include bleeding, pain, infection, and scarring.

Postoperative and Rehabilitation Care

After surgical removal of Pilar cyst, it is very important to taking care of the surgical site. Daily dressing is advisable along with normal saline and disinfectant solution, covering the sutures with gauze is recommended for the first very days. Typically, sutures should be removed in 7 to 10 days depending on the site of the cyst and status of the wound.

Consultations

Pilar cyst is purely cutaneous condition and does not require consultations to any other specialties unless there is a comorbid disease or any additional complications.

Pearls and Other Issues

Trichilemmal cysts are benign lesions, and they might transform into malignancy on rare occasions. Head and neck are the commonest sites to be affected. Recurrences and metastases have been observed. If the surgeon does not remove the sac completely, then the recurrence rate will be high. Merkel cell carcinoma sometimes might arise from pilar cysts.

Enhancing Healthcare Team Outcomes

Assessment of any patients with Pilar cyst begins with members of an interprofessional team of nurses and physicians taking a thorough history and careful physical examination which is usually enough to reach the diagnosis in most of the cases. Rarely, biopsy of the lesion is needed for the diagnosis. Reassurance of the patient is very important. Patients who are interested in surgical treatment should be aware of the consequences of surgery since scar formation can be more disfiguring to the patient's image rather than the lesion itself.

Human skin is made up of several layers and sublayers. The two main layers are the epidermis and the dermis. These layers cover a third layer of tissue called the hypodermis, which consists of fibrous and adipose connective tissue (Figure 21.2).

The epidermis is the outermost layer of the skin, and it is relatively thin. The exterior surface of the epidermis, called the stratum corneum, primarily consists of dead skin cells. This layer of dead cells limits direct contact between the outside world and live cells. The stratum corneum is rich in keratin, a tough, fibrous protein that is also found in hair and nails. Keratin helps make the outer surface of the skin relatively tough and waterproof. It also helps to keep the surface of the skin dry, which reduces microbial growth. However, some microbes are still able to live on the surface of the skin, and some of these can be shed with dead skin cells in the process of desquamation, which is the shedding and peeling of skin that occurs as a normal process but that may be accelerated when infection is present.

Beneath the epidermis lies a thicker skin layer called the dermis. The dermis contains connective tissue and embedded structures such as blood vessels, nerves, and muscles. Structures called hair follicles (from which hair grows) are located within the dermis, even though much of their structure consists of epidermal tissue. The dermis also contains the two major types of glands found in human skin: sweat glands (tubular glands that produce sweat) and sebaceous glands (which are associated with hair follicles and produce sebum, a lipid-rich substance containing proteins and minerals).

Perspiration (sweat) provides some moisture to the epidermis, which can increase the potential for microbial growth. For this reason, more microbes are found on the regions of the skin that produce the most sweat, such as the skin of the underarms and groin. However, in addition to water, sweat also contains substances that inhibit microbial growth, such as salts, lysozyme, and antimicrobial peptides. Sebum also serves to protect the skin and reduce water loss. Although some of the lipids and fatty acids in sebum inhibit microbial growth, sebum contains compounds that provide nutrition for certain microbes.

Figure 21.2 (a) A micrograph of a section through human skin shows the epidermis and dermis. (b) The major layers of human skin are the epidermis, dermis, and hypodermis. (credit b: modification of work by National Cancer Institute)

Hair Follicle The slide shows a cross-section of a hair follicle. Basal cells of the hair matrix in the center differentiate into cells of the inner root sheath. Basal cells at the base of the hair root form the outer root sheath. LM × 4. (credit: modification of work by “kilbad”/Wikimedia Commons)

A sebaceous gland is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair. Most sebaceous glands are associated with hair follicles. They generate and excrete sebum, a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable. The fatty acids of sebum also have antibacterial properties, and prevent water loss from the skin in low-humidity environments. The secretion of sebum is stimulated by hormones, many of which do not become active until puberty. Thus, sebaceous glands are relatively inactive during childhood.

Hair Hair follicles originate in the epidermis and have many different parts.

While the microbiota of the skin can play a protective role, it can also cause harm in certain cases. Often, an opportunistic pathogen residing in the skin microbiota of one individual may be transmitted to another individual more susceptible to an infection. For example, methicillin-resistant Staphylococcus aureus (MRSA) can often take up residence in the nares of health care workers and hospital patients; though harmless on intact, healthy skin, MRSA can cause infections if introduced into other parts of the body, as might occur during surgery or via a post-surgical incision or wound. This is one reason why clean surgical sites are so important.

Injury or damage to the skin can allow microbes to enter deeper tissues, where nutrients are more abundant and the environment is more conducive to bacterial growth. Wound infections are common after a puncture or laceration that damages the physical barrier of the skin. Microbes may infect structures in the dermis, such as hair follicles and glands, causing a localized infection, or they may reach the bloodstream, which can lead to a systemic infection.

In some cases, infectious microbes can cause a variety of rashes or lesions that differ in their physical characteristics. These rashes can be the result of inflammation reactions or direct responses to toxins produced by the microbes. It is important to note that many different diseases can lead to skin conditions of very similar appearance; thus the terms used in the table are generally not exclusive to a particular type of infection or disease.