Steatocystoma Multiplex: A Rare Skin Condition with a Tendency to Develop Multiple Cysts

What Is a Sebaceous Cyst?

A sebaceous cyst is a benign cystic tumor arising from the sebaceous glands, which are responsible for secreting sebum [1,2]. Formally referred to as a “sebaceous cyst,” it is classified as a type of skin adnexal tumor [1,11]. Sebaceous cysts are a relatively uncommon skin condition, estimated to account for approximately 1–2% of all skin tumors [2,14].

Solitary sebaceous cysts occur sporadically, whereas multiple cysts are strongly associated with hereditary diseases [4,5,7]. In particular, hereditary tumor syndromes such as Muir-Torre syndrome are known to feature multiple sebaceous tumors as a characteristic cutaneous manifestation [4,5,9,10].

 

Epidemiology and Incidence of Sebaceous Cysts

Sebaceous cysts are a relatively uncommon condition, with an estimated annual incidence of approximately 0.5–1 case per 100,000 population [2,14]. There is little difference in incidence between males and females, and while they occur across a wide age range, onset in adulthood is more commonly observed [1,2].

Predilection sites include areas rich in sebaceous glands: the anterior chest (approximately 40%), the axillae (approximately 25%), and the neck (approximately 20%) [14]. They may also develop on the face and scalp, although secondary development from nevus sebaceus should be considered at these locations [15,17].

 

Genetics and Molecular Biology of Sebaceous Cysts

Solitary sebaceous cysts are typically sporadic, while genetic factors play an important role in multiple sebaceous cysts [7]. Mutations in the keratin 17 (K17) gene, which follow an autosomal dominant inheritance pattern, have been reported; these mutations are thought to cause abnormal differentiation of the sebaceous glands [7].

In Muir-Torre syndrome, mutations in DNA mismatch repair genes (MSH2, MLH1, MSH6, PMS2) give rise to a characteristic combination of sebaceous tumors and visceral cancers, particularly colorectal cancer [4,5,9,10]. In this syndrome, sebaceous tumors—including sebaceous cysts—serve as important cutaneous warning signs [5,13].

 

Histopathological Features and Diagnosis

The histopathological features of sebaceous cysts are characterized by a cyst wall composed of mature sebaceous cells and sebum-like material within the cyst cavity [2,12]. Immunohistochemically, positivity for sebaceous markers such as adipophilin and perilipin-1 is useful in confirming the diagnosis [2,12].

The most important differential diagnosis is distinction from an epidermoid cyst (atheroma) [1,3]. Epidermoid cysts characteristically display a central punctum (umbilication), whereas sebaceous cysts do not [1]. The tendency toward multiple lesions is also a helpful distinguishing feature [14].

 

Causes of Sebaceous Cysts

Sebaceous cysts are thought to develop as a result of obstruction of the sebaceous gland opening or duct, which prevents normal secretion of sebum [1,2]. In solitary cases, the condition is non-hereditary, and secondary ductal obstruction due to trauma or inflammation is often identified as the cause [1].

In multiple sebaceous cysts, genetic factors are important; mutations in the keratin 17 (K17) gene with autosomal dominant inheritance have been reported [7]. These mutations lead to abnormal differentiation of the pilosebaceous unit, resulting in multiple sebaceous cysts [7].

Sebaceous cysts may also develop secondarily from nevus sebaceus [15,17]. In such cases, hormonal changes after puberty may activate the nevus sebaceus, with the potential development of various sebaceous tumors (including sebaceous cysts, sebaceous adenomas, and sebaceous carcinomas) [15,17].

 

Symptoms of Sebaceous Cysts

Sebaceous cysts commonly develop in areas rich in sebaceous glands, including the anterior chest, axillae, and neck [1,14]. They present as skin-colored to pale yellow, hemispheric, elevated nodules with a smooth surface and mobility on palpation [1,2].

The most characteristic feature of sebaceous cysts is their tendency toward cluster formation, with multiple cysts developing in close proximity [14]. Although solitary cysts occur, new cysts frequently appear in the surrounding area over time [14].

Sebaceous cysts are generally asymptomatic; however, if the cyst wall ruptures and inflammation occurs, swelling and pain may develop [1,3]. Rupture allows sebum-like contents to leak into the surrounding tissue, where inflammatory granulation tissue may form [1].

An important distinguishing feature from epidermoid cysts (atheromas) is the absence of a central punctum (umbilication) in sebaceous cysts [1]. The tendency toward multiple lesions is also a useful finding in differentiation from epidermoid cysts [14].

 

Diagnosis and Examination of Sebaceous Cysts

Diagnosis of sebaceous cysts is primarily based on clinical features [1,11]. On inspection, the lesion appears as a skin-colored to pale yellow hemispheric nodule; on palpation, it is felt as a soft, elastic, and mobile mass [1].

Imaging studies such as ultrasound can depict the lesion as a cystic mass with a uniform hypoechoic area internally [16]. On MRI, the lesion characteristically shows signal intensity equivalent to fat on T1-weighted images, and high signal intensity on T2-weighted images as well [16].

Histopathological examination is required for a definitive diagnosis, with confirmation of a cyst wall composed of mature sebaceous cells being essential [2,12]. Immunohistochemical examination demonstrates positivity for sebaceous markers such as adipophilin and perilipin-1 [2,12].

In cases of multiple sebaceous cysts, the possibility of hereditary tumor syndromes such as Muir-Torre syndrome should be considered, and it is important to take a thorough family history and consider genetic testing [4,5,13].

 

Treatment Options for Sebaceous Cysts

Surgical excision is the definitive treatment for sebaceous cysts [3,16]. Complete removal including the cyst wall helps reduce the likelihood of recurrence [3,16]. Surgery is performed under local anesthesia, with the incision line determined according to the size and location of the cyst [16].

Aspiration of the cyst contents provides temporary reduction, but because the cyst wall remains, recurrence is common [3]. Therefore, surgical excision is generally recommended as the preferred approach even when symptom relief is the primary goal [3,16].

For multiple sebaceous cysts, the treatment plan is determined based on a comprehensive assessment of both cosmetic and functional considerations [14]. Since it is often not practical to remove all cysts at once, a staged approach is commonly adopted according to the patient’s preferences and the severity of symptoms [14].

Carbon dioxide (CO₂) laser treatment is another option; however, since complete removal of the deep cyst wall may not always be achieved, the risk of recurrence must be carefully considered when determining its suitability [16].

 

Post-Treatment Course and Prognosis

With appropriate surgical excision, the prognosis is generally favorable; the recurrence rate following complete removal has been reported to be below 5% [3,16]. Post-operative complications are uncommon, and when they do occur, they tend to be mild, such as temporary swelling or minor discomfort [16]. For multiple sebaceous cysts associated with hereditary conditions such as Muir-Torre syndrome, regular dermatological follow-up and general medical screening (including colorectal cancer screening) are important [4,5,13].

 

Complications and Precautions

The main complication of sebaceous cysts is inflammation resulting from rupture of the cyst wall [1,3]. Rupture causes sebum-like contents to leak into the surrounding tissue, triggering a foreign-body inflammatory reaction [1].

In cases of multiple sebaceous cysts, the possibility of hereditary tumor syndromes such as Muir-Torre syndrome should always be kept in mind [4,5,13]. In this syndrome, sebaceous tumors may present as a warning sign of colorectal or urogenital cancer, making early detection and treatment particularly important [5,10].

Sebaceous cysts arising in association with nevus sebaceus carry a risk of malignant transformation (sebaceous carcinoma) after puberty, and regular monitoring is therefore necessary [15,17,18]. If rapid enlargement or ulceration is observed, a tissue biopsy should be performed promptly [17,18].

 

Surgical Costs for Sebaceous Cysts

Frequently Asked Questions About Sebaceous Cysts

Q: Can sebaceous cysts resolve on their own?

A: Sebaceous cysts rarely resolve on their own [1,3]. As long as the cyst wall remains, contents will re-accumulate, leading to recurrence [3]. Surgical excision is required for definitive treatment [3,16].

 

Q: What is the difference between a sebaceous cyst and an epidermoid cyst (atheroma)?

A: The most important distinguishing feature is that epidermoid cysts characteristically have a central punctum (umbilication), whereas sebaceous cysts do not [1]. In addition, sebaceous cysts tend to present as multiple lesions, which is another useful finding for differentiation [14].

 

Q: In cases of multiple sebaceous cysts, is there a possibility of a hereditary disease?

A: Multiple sebaceous cysts may be associated with hereditary tumor syndromes such as Muir-Torre syndrome [4,5]. In such cases, there is an elevated risk of concurrent visceral cancers such as colorectal cancer, and genetic counseling and consideration of genetic testing are recommended [5,13].

 

Q: What is the recurrence rate after surgery?

A: When complete excision including the cyst wall is performed, the recurrence rate is reported to be below 5%, reflecting a favorable outcome [3,16]. However, incomplete excision or aspiration alone is associated with a higher likelihood of recurrence, which is why appropriate surgical treatment is important [3].

References

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