The lymphatic system is a complex network of vessels and nodes that maintains fluid balance and supports immune function by collecting excess fluid, known as lymph, and returning it to the bloodstream. A lymphatic malformation (LM) is a rare, congenital mass originating from errors within this system. LMs are benign lesions, meaning they are not cancerous, but their presence can still lead to significant health challenges depending on their size and location.
Defining Lymphatic Malformations
A lymphatic malformation is a developmental abnormality of the lymphatic vessels resulting in a cluster of disorganized, fluid-filled sacs or cysts. These sacs form because the lymphatic channels failed to connect properly to the body’s drainage network during embryonic development. This lack of drainage causes fluid to accumulate, distending the abnormal vessels and forming a noticeable mass. LMs are classified as slow-flow vascular malformations and are present at birth, though they may not become apparent until later in childhood. They represent a defect in the formation of normal tissue structures rather than uncontrolled cell proliferation.
Classification Based on Structure and Location
LMs are primarily categorized based on the size of the cysts they contain.
Classification by Structure
Macrocystic lesions are composed of large, distinct cysts, typically measuring more than two cubic centimeters in volume. Microcystic malformations are characterized by small, numerous cysts that are often described as sponge-like and tend to infiltrate surrounding tissue. Many lymphatic malformations are classified as mixed lesions, containing both macrocystic and microcystic components within the same mass.
Classification by Location
Lymphatic malformations can develop anywhere in the body, but they show a strong preference for the head and neck region, occurring there in approximately 75 percent of cases. Other common sites include the torso, limbs, and internal organs. The malformation’s location is a determining factor for potential complications, such as a large lesion in the neck causing pressure on the airway or difficulty with swallowing. The extent to which the malformation infiltrates normal tissue also impacts the difficulty of surgical removal and the likelihood of successful treatment.
Origins and Diagnostic Procedures
Origins
Lymphatic malformations are congenital, arising from errors in the formation of the lymphatic system during early fetal development. They usually occur sporadically, meaning they are not inherited, although associations with certain genetic syndromes exist. Recent scientific analysis suggests that a significant number of LMs are linked to somatic mutations in genes such as PIK3CA. These changes occur after conception and affect only the cells of the malformation itself, explaining the localized, non-inherited nature of many malformations.
Diagnostic Procedures
The diagnostic process typically begins with imaging studies to confirm the presence and map the extent of the lesion. Ultrasound is frequently used as an initial screening tool, as it can easily distinguish the fluid-filled cystic structures from solid masses. For detailed mapping, Magnetic Resonance Imaging (MRI) is the preferred technique. MRI provides high-resolution images that clearly show the relationship between the LM and adjacent structures, such as nerves, muscles, and blood vessels, which is necessary for planning intervention.
Interventional and Supportive Care
Management is tailored to the lesion’s type, size, and the symptoms it causes. For small, stable lesions that do not interfere with function, careful observation may be appropriate. Intervention is recommended when the malformation causes pain, recurrent infection, or functional issues like difficulty breathing or eating.
Sclerotherapy
The primary non-surgical treatment is sclerotherapy, a minimally invasive procedure performed by an interventional radiologist. This involves aspirating fluid from the cysts and injecting a sclerosing agent directly into the malformation. Agents such as doxycycline, bleomycin, or OK-432 irritate the lining of the abnormal vessels. This triggers an inflammatory response that causes the cyst walls to collapse and scar down, reducing the size of the lesion. Sclerotherapy is often the first-line treatment for macrocystic lesions.
Surgical Excision and Supportive Care
Surgical excision is reserved for lesions that do not respond to sclerotherapy or for those that are well-defined and can be removed without undue risk to surrounding structures. Complete surgical removal is often challenging, particularly with microcystic or infiltrating lesions, due to the risk of damaging nerves or other healthy tissue. Supportive care focuses on treating complications such as cellulitis, a common bacterial infection associated with LMs, and addressing any potential compromise to the airway.