A Lymphatic Malformation (LM) is a rare, benign, and congenital anomaly of the lymphatic system. This network of vessels and nodes manages the body’s fluid balance and immune function by collecting lymph and returning it to the bloodstream. LMs are characterized by an abnormal cluster of vessels that fail to connect correctly to the network. This structural error causes lymph fluid to pool, resulting in a mass typically present at birth or appearing early in childhood.
What Lymphatic Malformations Are and How They Form
Lymphatic malformations are not cancerous and are classified as vascular malformations. They arise from a developmental error (dysplasia) in the lymphatic vessels during early fetal development. Instead of forming a functional network, the vessels become disorganized and blocked, forming a spongy cluster of cysts that cannot drain fluid effectively.
This abnormal development is generally sporadic, occurring randomly rather than being inherited. Some LMs are linked to somatic mutations in genes like PIK3CA, which play a role in cell growth. Due to this abnormal structure, the malformation grows with the child and does not shrink or regress on its own over time.
The abnormal vessels are often fragile and may contain small veins, causing them to bleed easily. When bleeding occurs, the cysts can quickly fill with blood or lymph fluid, leading to a sudden and painful increase in size, sometimes called a “flare.” This inability to properly drain the lymph fluid leads to the characteristic spongy, fluid-filled mass.
Classification of Lymphatic Malformations
Classification is based on the size of the abnormal cysts, which helps determine the most effective treatment strategy. The International Society for the Study of Vascular Anomalies (ISSVA) system categorizes LMs primarily into three types.
Macrocystic LMs are defined by having large cysts, generally measuring more than one centimeter in diameter. They often present as a soft, compressible mass under the skin and were historically called cystic hygromas when found in the neck. Macrocystic lesions respond predictably to non-surgical treatments because the cystic fluid is easily accessible.
Microcystic LMs consist of many small, diffuse cysts, typically less than one centimeter in diameter. These lesions tend to be firmer and more infiltrative, weaving through surrounding tissues like muscle and fat. This pervasive nature makes them challenging to treat surgically because complete removal without damaging healthy tissue is often impossible.
Mixed lymphatic malformations contain a combination of both large macrocysts and small microcysts. The treatment plan must address both the larger, drainable cysts and the smaller, more infiltrative components. The morphology dictates the complexity of management and the likelihood of recurrence following intervention.
Identifying Symptoms and Diagnostic Methods
Lymphatic malformations are usually visible at birth or become apparent within the first two years of life, presenting as a soft, spongy lump. While they can occur anywhere, the most common location is the head and neck region, accounting for approximately 75% of all cases. Symptoms depend on the size and location, ranging from a cosmetic concern to serious functional impairment.
When an LM is located near vital structures, such as the mouth, orbit, or neck, it can cause complications. These complications include difficulty swallowing, breathing problems, or vision impairment. A sudden expansion due to infection or internal bleeding can lead to acute pain and swelling, requiring urgent medical attention.
Diagnosis begins with imaging studies to accurately map the malformation and its relationship to surrounding structures. Ultrasound is often the initial tool used to confirm the cystic nature of the mass. Magnetic Resonance Imaging (MRI) provides the most detailed information, outlining the extent of the lesion, its classification (macrocystic or microcystic), and its involvement with adjacent tissues. Biopsy is rarely required because imaging characteristics are usually sufficient to confirm the diagnosis and guide treatment.
Treatment and Long-Term Management
The management approach is tailored to the lesion’s size, location, and classification. Small, asymptomatic LMs are often managed with observation and periodic imaging to monitor for growth. When intervention is necessary, the primary goal is to control symptoms, preserve function, and improve appearance.
Sclerotherapy is a minimally invasive treatment that is often the first-line option, especially for macrocystic and mixed lesions. This procedure involves puncturing the cyst, draining the fluid, and injecting a sclerosant agent into the space to induce inflammation and fibrosis. This causes the cyst walls to collapse and scar down. Common sclerosant agents include doxycycline, bleomycin, and ethanol, which intentionally damage the abnormal vessel lining.
Surgical excision is reserved for cases where sclerotherapy has failed or when the malformation causes significant functional impairment requiring immediate removal. Surgery for microcystic LMs is difficult because the lesion infiltrates surrounding tissues, making complete removal challenging and increasing the risk of damage to nearby structures. Recurrence remains a concern, especially with incompletely removed microcystic lesions, necessitating long-term follow-up and monitoring.