A lymphoepithelial cyst is a benign, slow-growing mass that can develop in various parts of the head and neck. These cysts are characterized by a distinct structure composed of epithelial tissue, which forms the cyst lining, enclosed by a dense collection of lymphoid tissue. The contents of the cyst are a clear, serous fluid or a thicker, mucoid substance. They are acquired lesions, meaning they develop over time and are not present at birth.
Common Locations and Symptoms
Lymphoepithelial cysts are most frequently discovered in the head and neck region, with a particular prevalence in the parotid glands, which are the large salivary glands located in the cheeks in front of the ears. These cysts can also appear in the submandibular glands under the jaw, or within the oral cavity itself, on the floor of the mouth or the tongue. Their size can vary significantly, ranging from a small, barely noticeable lump of 0.5 centimeters to a much larger mass of up to 5.0 centimeters.
Many individuals with a lymphoepithelial cyst experience no symptoms at all, and the discovery is often incidental during a routine physical or dental examination. When symptoms are present, they manifest as a single, painless swelling that is mobile under the skin. The texture of the lump can range from soft and fluctuant to firm. In rare cases, if the cyst becomes infected, it may become painful.
Underlying Causes and Associations
The precise origin of lymphoepithelial cysts is not fully understood, but the leading theory suggests they form from the entrapment of epithelial tissue, such as salivary gland ducts, within a lymph node. This entrapment is thought to happen during embryonic development. Over time, the trapped epithelial cells can proliferate and accumulate fluid, leading to the cystic structure surrounded by the native lymphoid tissue of the node.
A significant association has been established between the development of these cysts and human immunodeficiency virus (HIV) infection. The presence of multiple cysts, particularly when they appear in both parotid glands, is a well-recognized clinical indicator that can be associated with HIV. In this context, the cysts are believed to result from lymphoid hypertrophy, or the overgrowth of lymphoid tissue, which can obstruct glandular ducts and lead to cyst formation. The appearance of these specific cysts may be one of the earlier signs of the underlying viral infection.
Diagnosis and Medical Evaluation
The diagnostic process begins with a physical examination of the head and neck, where a provider assesses the mass’s size, location, and consistency. Following the physical exam, imaging studies are commonly employed to visualize the lesion in greater detail. Ultrasound is often the initial imaging modality used, as it can effectively differentiate cystic (fluid-filled) structures from solid masses. For more detailed anatomical information, a computed tomography (CT) or magnetic resonance imaging (MRI) scan may be ordered.
A definitive diagnosis requires cellular analysis to rule out other conditions. This is achieved through a procedure called fine-needle aspiration (FNA). During an FNA, a thin needle is inserted into the cyst to withdraw a sample of fluid and cells, which is then examined under a microscope. The presence of squamous cells mixed with a rich population of lymphocytes is a characteristic finding. In some cases, a complete surgical removal, or excisional biopsy, may be necessary to confirm the diagnosis.
Treatment and Management Approaches
Once a lymphoepithelial cyst is diagnosed, the approach to management depends on several factors, including its size and whether it is causing symptoms. For small, asymptomatic cysts, a strategy of “watchful waiting” or simple observation may be recommended.
For cysts that are large, cause physical discomfort, are cosmetically deforming, or become recurrently infected, surgical excision is the most common and effective treatment. The procedure involves the complete removal of the cyst with a low chance of recurrence. Another option is aspiration, where the fluid is drained from the cyst with a needle. While aspiration can provide temporary relief from swelling, it is not a permanent solution, as the cyst lining remains and the fluid often reaccumulates.