A dermoid cyst is a sac-like pocket containing tissues normally found on the outer layer of the skin. These growths are congenital, meaning they are present from birth, and represent a common developmental anomaly. While they can arise anywhere in the body, their prevalence varies significantly depending on the specific location.
What Exactly Is a Dermoid Cyst?
A dermoid cyst is a benign tumor originating from the entrapment of ectodermal elements, or skin-forming cells, along the lines of embryonic closure during fetal development. This process sequesters a pocket of skin tissue beneath the surface, forming a cyst lined by stratified squamous epithelium. The cyst continues to grow slowly because the glands and follicles within its lining continue to produce secretions and mature cells.
The composition of a dermoid cyst is unique, often containing mature skin appendages such as hair follicles, sweat glands, and sebaceous glands. The inner space of the cyst is typically filled with a greasy, keratinous material, often mixed with hair. In ovarian dermoid cysts, tissues from all three embryonic germ layers may be present, sometimes including bone, cartilage, or fully formed teeth.
This type of cyst is a form of mature cystic teratoma, distinguishing it from simple fluid-filled cysts. Although present at birth, they may not be noticeable until later in life, growing slowly over many years as the trapped tissue continues its normal function.
Frequency Based on Location and Type
The frequency of dermoid cysts is highly dependent on where they develop in the body. The majority are found in superficial locations, where they are easily observed and diagnosed. Roughly 85% of all dermoid cysts are located in the head and neck region, making this the most common site of occurrence.
Most superficial dermoid cysts are diagnosed in childhood, often before the age of five. The most frequent site is the periorbital area, appearing near the lateral third of the eyebrow. They present as a firm, non-tender lump just under the skin, often causing concern for parents.
In internal organs, the prevalence shifts, particularly for ovarian dermoid cysts (mature cystic teratomas). In women of reproductive age, these cysts are the most common type of ovarian germ cell tumor, representing approximately 20% of all ovarian tumors. They are typically found in women between 15 and 40 years old and are often detected incidentally during routine pelvic imaging.
Deep-seated dermoid cysts, such as those found within the central nervous system, are significantly more rare but carry greater clinical importance. Intracranial or intraspinal dermoid cysts develop deep within the brain or along the spinal cord. Their location means that even slow growth can lead to serious neurological complications.
Symptoms, Diagnosis, and Outlook
Many dermoid cysts, especially small or superficial ones, remain asymptomatic for years. When symptoms occur, they are related to the size and location of the growth, often presenting as a palpable, painless lump near the skin’s surface. Internally located cysts may cause pain or pressure as they expand against surrounding tissues, such as pelvic pain in the case of a large ovarian cyst.
Complications can arise if the cyst becomes infected, ruptures, or causes the ovary to twist (torsion) in the case of ovarian dermoids. A cyst near the eye may cause noticeable swelling, and a spinal cyst may press on nerves, leading to neurological symptoms.
Diagnosis for superficial cysts is often confirmed through a physical examination due to their characteristic location. For deeper or more complex cysts, imaging studies determine the exact location and extent of the growth. Ultrasound is commonly utilized for ovarian cysts, while CT scans and Magnetic Resonance Imaging (MRI) provide detailed pictures of cysts near sensitive areas like the eye, spine, or brain.
The outlook for individuals with a dermoid cyst is positive. The standard treatment is surgical removal, which permanently resolves the issue and prevents future complications. While malignant transformation is possible, it is extremely rare, occurring primarily in mature cystic teratomas of the ovary.