What Is Sebaceous Cyst

Introduction

When you see a pronounced bump growing under your skin, you often think if I should pop it or get it checked out. More often than not, the bumps you see are harmless and they are called sebaceous cysts.¹

A sebaceous cyst is a benign bump protruding from the surface of the skin as a cause of blogged follicular orifice filled with keratin, a type of protein that is found on epithelial cells.¹ Contrary to its name, sebaceous cysts do not involve sebaceous glands.

It is often that sebaceous cysts are confused with tumours such as cystic basal cell carcinoma, lipoma, and other types of cutaneous cysts. Here, we will demystify the understanding of this type of cysts in both a clinical and a practical context.

Before you start to panic or poke the mysterious cyst that forms, we encourage you to explore what a sebaceous cyst is by reading:¹

• Causes of sebaceous cysts
• Signs and symptoms of sebaceous cysts
• Management and treatment for sebaceous cyst

Overview 

A sebaceous cyst is a misleading term used to identify cysts called epidermoid, as the cyst does not originate from sebaceous glands. An epidermoid or sebaceous cyst is the most common cutaneous cyst, with 70-80% occurrence, and often seen in male adults post-puberty.^1,3 Epidermoid cysts are slow-growing, benign, and painless masses that protrude from the skin which looks like a bump with a keratin-filled orifice or a punctum.¹ The underlying cause of the cysts can vary from penetrating injuries of the skin to obstruction of follicular orifices. The cyst is asymptomatic until it ruptures and releases its content which can cause infections and inflammation. An epidermoid cyst can be identified by its center punctum, which represents the pilosebaceous follicle, a follicle type referred to both hair follicles and sebaceous gland and its yellowish discharge.¹ The non-contagious cyst can be treated using surgical excision that removes the cysts content and lining to avoid recurrence in the future.¹ The management of infectious or persistence cysts, include the application of steroids or further excision by physicians. The risk of being diagnosed with tumours or other cutaneous cysts is low, but often associated with patient’s genetic history. Hence, a thorough diagnosis of sebaceous cysts should be confirmed through histopathologic examination.¹

Causes of sebaceous cysts 

Epidermoid or sebaceous cysts can be caused by rupture of the follicle related to acne, skin penetrating injuries, bloggage of follicular orifices and other etiology factors. Plugging of the follicular orifice often leads to epidermoid forming. The epidermoid cyst wall is lined with stratified squamous epithelium that is caused by the peeling of keratin layers that accumulate inside the cyst.^1,3

The cysts can also be grown from the part of the hair follicle that connects the hair shaft to the sebaceous glands, known as follicular infundibulum. The infundibulum is responsible for oil, also known as sebum, produced by the sebaceous gland to lubricate the hair shaft on the surface of the skin to prevent skin dryness. A common misconception that the epidermoid cysts occur from overproduction of sebum, can be explained by the cyst’s association with acne vulgaris. The cysts can occur spontaneously as a part of acne vulgaris. Acne vulgaris is an acne that persists through adulthood as a result of overproduction of sebum and hyperproliferation of follicular epidermis in adolescence.² Obstruction of the follicular orifice can cause multiple epidermoid cysts originating from acne vulgaris that came undone to form. Typically, the cysts are asymptomatic until they rupture and release the contents of the cysts, soft and yellow-ish keratin, into the dermis and surrounding tissues. The cystic rupture causes inflammation which is associated with ultra-violet (UV) light exposure and infection of human papillomavirus (HPV).^1,3

Skin injuries that are penetrated can lead to implanting of epithelium in the lesions and cause epidermoid cysts formation called epidermal inclusion cysts. However, the majority of epidermoid cyst formation is sporadic. Epidermoid cysts which occur prior to puberty are often associated with genetic syndromes such as Gardner syndrome (familial adenomatous polyposis), an autosomal dominant genetic disease, and Gorlin syndrome (basal cell nevus syndrome).^5,6 In cases of elderly patients, Favre-Racouchot syndrome (nodular elastosis with cysts) has been associated with the cysts forming as a result of chronic sun exposure.^1,3

Signs and symptoms of sebaceous cysts 

Epidermoid or sebaceous cysts are characterised clinically as a non-fluctuant, compressible mass with 0.5 cm in size. The center of the cyst is often a dark blackhead with a noticeable punctum. The cysts also resembles a furuncle with palpation, swlling, and erythema. Once ruptured, a foul smell and release of yellowish cheese-like discharges from the skin are described. The physical signs or symptoms of the cysts may not be pronounced until a rupture occurs, which can be caused by a fall or someone slapping their back.^1,3

The location of the epidermoid varies between the patients, but they are commonly found in the face, neck, upper back, chest, genitals, and scrotum. The cysts can also be found on the buttocks, palms, and plantar side of the feet from a penetrated injury. The cysts' formation on the distal portion of the fingers can lead to changes to the nail plate. The cysts may be caused by medications or a part of a genetic syndrome, depending on the etiology and histological examinations.^1,3 The epidermoid cyst may often be confused with other cutaneous tumours or cysts as aforementioned. An epidermoid cyst is protruding and has a firmness, unlike lipoma. The lack of central punctum also distinguishes it from basal cell carcinoma and trichilemmal cysts.^1,3

Management and treatment for sebaceous cysts

Although epidermoid cysts are asymptotic and does not need treatment if occur in small sizes, the cysts can be treated with surgical excision. The excision is an intrusive procedure to the skin and should be delayed if an active infection occurs that may cause difficulting during the operation. An intralesional steroid injection may help reduce inflammation in additiona to the delay of the operation.^1,3 The initiate incision and drainage may indicate a reoccurence in the future, and should be administer after epinephrine to minimise bleeding. To yield the best cosmetic results, the incision should be minimal on the skin lines. A multiple-layered subcuticular and epidermal closure are important to receive the best outcome.^1,3 The cyst rupture and detached cyst lining are important factors that prevent the recurrence of the cysts. However, prior to the treatment, all epidermoid cysts removed for biopsy should be subjected to histopathological analysis, to avoid misdiagnosis and ensure complete excision.^1,3

In the cases where the lesions persist and become transient lesions called milium, topical retinoids may be used for multiple facial lesions and incisions of the overlying epidermis are methods of milium removal by physicians.^1,3

FAQs 

How common are sebaceous cysts

Epidermoid or sebaceous cysts are the most common cutaneous cysts, with 70-80% occurence.^1,3

Who are at risk of sebaceous cysts

Epidermoid or sebaceous cysts are common in adults and rare in adolescence before puberty. It is predominantly found in males than in females.^1,3

Are sebaceous cysts contagious

Sebaceous cysts are not contagious. Only one percent of epidermoid cysts become malignant.^1,3

How are sebaceous cysts diagnosed

Diagnosis of sebaceous cysts can be confirmed through histopathology, examination of the affected tissue or cell under a microscope. Clinical and imaging features, including identification of the cyst location, may also serve as a diagnostic indicator. Epidermoid or sebaceous cysts are identified as stratified squamous epithelium, surrounded by a stratified epithelial cell wall.^1,3

How can I prevent sebaceous cysts

There are no epidermoid cysts preventative methods, but it is important to avoid rupturing of the cysts once occurs to prevent infection and scarring.^1,3

When should I see a doctor

Physician consultations are not necessary unless the cyst appears large or in an unusual location such as the mouth or face. Adults with a history of multiple lipomas or colon cancer should consult a specialist of Gardner syndrome suspicion.^1,3

Summary

Sebaceous or epidermoid cyst is the most common cutaneous cyst that is commonly found in male adults post-puberty. The cyst is a benign and slow-growing mass like a bump from the skin filled with keratin which is identified as a punctum. The common causes of epidermoid cysts are obstruction of follicular orifices, rupture of acne-related cysts, and penetrating skin injuries. The asymptomatic cyst can cause skin infection and inflammation such as HPV from rupturing or sunlight exposure. The epidermoid cysts are distinguished from other cysts or a tumour by their punctum and the content discharged. Treatment of the cysts includes removal of cyst content and lining with surgical excision, preventing recurrence or milium. Application of topical steroids and further excision are options to manage infection cysts. The risk of tumour diagnosis from the cysts is low but can be associated to patients with lipoma or other medical histories. Hence, a histopathologic examination is recommended to confirm the epidermoid cysts.  

References

1. Baykal, Can, and K. Didem Yazganoğlu. Clinical Atlas of Skin Tumors. Springer Berlin Heidelberg, 2014. DOI.org (Crossref), https://doi.org/10.1007/978-3-642-40938-7.
2. Crawford, Sybil, et al. ‘Circulating Dehydroepiandrosterone Sulfate Concentrations during the Menopausal Transition’. The Journal of Clinical Endocrinology & Metabolism, vol. 94, no. 8, Aug. 2009, pp. 2945–51. DOI.org (Crossref), https://doi.org/10.1210/jc.2009-0386.
3. Hoang, Van Trung, et al. ‘Overview of Epidermoid Cyst’. European Journal of Radiology Open, vol. 6, Jan. 2019, pp. 291–301. www.ejropen.com, https://doi.org/10.1016/j.ejro.2019.08.003.
4. Zito, Patrick M., and Richard Scharf. ‘Epidermoid Cyst’. StatPearls, StatPearls Publishing, 2023. PubMed, http://www.ncbi.nlm.nih.gov/books/NBK499974/.
5. Panjwani, Sapna, et al. ‘Gardner’s Syndrome’. Journal of Clinical Imaging Science, vol. 1, Dec. 2011, p. 65. PubMed Central, https://doi.org/10.4103/2156-7514.92187.CloseDeleteEdit
6. Spiker, Alison M., et al. ‘Gorlin Syndrome’. StatPearls, StatPearls Publishing, 2023. PubMed, http://www.ncbi.nlm.nih.gov/books/NBK430921/.

This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Suchavadee Liangteva

Masters of Science in Stem Cells & Regenerative Therapies - MSc, King’s College London

Pim is a content creator of Stem Cells research and technologies, with roots in biochemistry and commercialisation of cell and gene therapies. She has a wide range of communications experiences in retail business, life sciences, digital marketing, and working directly with health care providers from Bangkok hospital ER department. She is currently working with University professors and students for guest episodes on her educational podcast and website in stem cells topics called ’Seriously Stem Cells’.

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