Steatoma, often called a true sebaceous cyst, is a benign, non-cancerous growth that forms just beneath the skin’s surface. These growths originate from the pilosebaceous unit, which includes the hair follicle and its associated oil gland. Steatomas are characterized by a sac-like structure filled with an oily substance produced by the sebaceous glands. The condition is generally harmless, though the presence of these cysts can sometimes lead to discomfort or cosmetic concerns. Understanding the nature of steatomas provides clarity for those affected.
Defining Steatoma and Its Characteristics
A steatoma is a cyst derived from the sebaceous duct, distinguishing it from the more common epidermal inclusion cyst. These lesions are unique because their inner lining, or cyst wall, contains sebaceous glands that continuously produce sebum, an oily, yellowish substance. When a steatoma is punctured or ruptured, this characteristic oily, semi-fluid content is released.
The cysts typically present as smooth, dome-shaped nodules that are soft or firm to the touch and are freely movable beneath the skin. While they can range up to several centimeters, most steatomas are relatively small, often between 2 and 20 millimeters. Unlike some other skin cysts, steatomas generally lack a central dark pore or punctum on the overlying skin.
Steatomas frequently appear in areas rich in sebaceous glands, most commonly the trunk, neck, upper arms, armpits, face, and sometimes the scrotum. A single occurrence is termed steatocystoma simplex, but the condition is often characterized by numerous cysts, known as steatocystoma multiplex.
Understanding the Underlying Causes
The formation of steatomas is directly related to the pilosebaceous unit. The development of multiple lesions is frequently linked to Steatocystoma Multiplex, an autosomal dominant inherited disorder. This means a person only needs to inherit one copy of the altered gene from one parent to develop the condition. The onset of these multiple cysts often occurs around adolescence, suggesting hormonal changes may trigger their growth.
The genetic basis involves mutations in the KRT17 gene, which provides instructions for making Keratin 17. This protein is a component of the structural support network within cells of the sebaceous glands and hair follicles. Defective Keratin 17 disrupts the normal function and growth of the sebaceous gland cells, leading to the formation of sebum-filled cysts.
In cases where only a single steatoma forms (steatocystoma simplex), the cause is often sporadic, meaning it occurs without a clear genetic link. These solitary lesions may arise from a localized obstruction of the sebaceous duct, which traps and accumulates sebum. Even in the multiple lesion form, a significant number of cases are considered sporadic, occurring in individuals with no prior family history.
Treatment and Professional Management
Treatment for steatomas is typically sought for cosmetic reasons or when the cysts become inflamed, infected, or cause physical discomfort. Since steatomas are benign, medical intervention is usually elective unless complications arise, such as a painful inflammatory reaction. If a cyst becomes infected, it can increase in size, become tender, and may require initial treatment with antibiotics before removal.
The definitive approach involves the physical removal of the cyst, as the lesions generally do not resolve on their own. For single or large lesions, traditional surgical excision is an option, though this method can result in scarring. A more common and cosmetically favorable technique, especially for multiple lesions, involves making a minimal incision, such as a 1 to 3-millimeter puncture.
Through this small opening, the oily cyst contents are expressed, and the entire cyst wall is carefully removed. Removing the complete cyst wall is paramount to prevent the steatoma from recurring. Alternative minimally invasive methods include carbon dioxide laser ablation, which is effective for treating numerous lesions in a single session with good aesthetic results. Aspiration using a fine needle can also be used, particularly for smaller lesions, but this technique carries a higher risk of recurrence if the cyst wall is left behind.