What is a Sebaceous Cyst?
A
sebaceous cyst, also known as an epidermoid cyst or keratin cyst, is a benign, slow-growing lump that forms beneath the skin. It is typically filled with a thick, yellow, cheesy-like substance composed of sebum and keratin. These cysts are usually found on the face, neck, and trunk but can occur anywhere on the body.
Histological Composition
The wall of a sebaceous cyst is lined by a thin, stratified squamous epithelium, similar to the epithelium found in the outer layers of the skin. The cyst content is a mixture of keratin, lipid-rich debris, and sebum, which is produced by the sebaceous glands. The cyst wall may also contain pilosebaceous units, which include hair follicles and sebaceous glands.Formation Mechanism
Sebaceous cysts form due to the obstruction of sebaceous glands or hair follicles, leading to the accumulation of sebum and keratin. This obstruction can be caused by trauma, infection, or genetic predispositions. The blocked gland continues to produce sebum, which collects within the cyst, gradually increasing its size.Histological Features
Under the microscope, a sebaceous cyst is characterized by a well-defined cystic structure. The lining of the cyst consists of stratified squamous epithelium, which may show varying degrees of keratinization. The lumen of the cyst contains lamellated keratinous material, and in some cases, lipid-laden macrophages or giant cells may be present due to the body's immune response to the cyst's contents.Clinical Presentation
Clinically, sebaceous cysts appear as smooth, round nodules beneath the skin. They are usually painless but may become tender, red, and inflamed if infected. The size of the cyst can vary from a few millimeters to several centimeters in diameter.Diagnosis
Diagnosis of a sebaceous cyst is typically based on clinical examination. However, histological examination is essential for confirming the diagnosis and ruling out other conditions such as lipomas or malignant cysts. Fine-needle aspiration or biopsy may be performed to obtain a sample for histological analysis.Treatment Options
Treatment of sebaceous cysts often involves surgical removal, especially if the cyst is large, painful, or infected. The entire cyst wall must be excised to prevent recurrence. In cases of infection, antibiotics may be prescribed, and the cyst may be drained before definitive surgical treatment.Prognosis
Sebaceous cysts are generally benign and have an excellent prognosis following complete surgical removal. However, incomplete excision can lead to recurrence. Regular follow-up is recommended to monitor for any signs of recurrence or complications.Histopathological Variants
While most sebaceous cysts are straightforward in their histological appearance, some variants may be encountered. These include proliferating trichilemmal cysts, which show rapid growth and cellular proliferation, and steatocystoma multiplex, characterized by multiple sebaceous cysts.Conclusion
Understanding the histological features of sebaceous cysts is crucial for accurate diagnosis and effective treatment. The cyst's lining, contents, and potential complications should all be carefully evaluated under the microscope. Proper surgical management ensures a favorable outcome and minimizes the risk of recurrence.
