Lymphatic System

The Lymphatic System

Overview and Definition

The lymphatic system is a subsystem of the circulatory system in the vertebrate body that consists of a complex network of vessels, tissues, and organs. It is an important and often underappreciated component of the circulatory, immune, and metabolic systems, composed of lymphatic fluid, lymphatic vessels, and lymphatic cells. Its main function is to return lymph from the tissues back into the bloodstream, and it is considered part of both the circulatory and immune systems.

The lymphatic system is fundamentally important to cardiovascular disease, infection and immunity, cancer, and probably obesity — the four major challenges in healthcare in the 21st century. Despite this significance, the lymphatic system is arguably the most neglected bodily system, and as a result, its contribution to human health and disease is not well understood.

Components and Anatomy

Major Structural Components

Components of the lymphatic system include lymph, lymphatic vessels and plexuses, lymph nodes, lymphatic cells, and various lymphoid organs. The pattern and form of lymphatic channels are more variable and complex, but generally parallel those of the peripheral vascular system.

Lymph Fluid

The lymphatic system regulates the balance of fluids in the body and filters pathogens from the blood. When the interstitial fluid gets absorbed into the lymphatic capillaries, it becomes the lymph. Similar to blood plasma, lymph is composed mainly of water. The other components are proteins, lipids, glucose, ions, and cells. Depending on where the lymph is produced, the composition can vary — for example, lymph produced in the gastrointestinal system is rich in fats. The lymphatic system maintains tissue fluid balance by draining approximately 2–4 litres of protein-rich interstitial fluid on a daily basis through specialized vessels equipped with intrinsic contractility and unidirectional valves.

Lymphatic Vessels

The lymphatic system consists of initial capillaries, collecting vessels, trunks, and lymph nodes that transport lymph, a fluid rich in proteins, immune cells, lipids, and metabolic waste. Lymphatic capillaries are thin-walled, blind-ended structures made up of a single-cell layer of endothelial cells joined by discontinuous button-like junctions that open in response to increased interstitial fluid pressure. The lymphatic vessels begin as open-ended capillaries, which feed into larger and larger lymphatic vessels, and eventually empty into the bloodstream by a series of ducts.

Collecting vessels have intraluminal valves as well as pericytes. The pericytes contain alpha-smooth muscle actin, which functions to contract the vessel and pump the fluid further through the system. A major distinction between the lymphatic and cardiovascular systems is that lymph is not actively pumped by the heart, but is forced through the vessels by the movements of the body, the contraction of skeletal muscles during body movements, and breathing.

Lymph Nodes

Lymph travels through the lymph nodes, which are commonly found near the groin, armpits, neck, chest, and abdomen. Humans have about 500–600 lymph nodes throughout the body. Lymph nodes play a pivotal role in the initiation of immune responses by detecting microbial components and foreign substances present in the lymph. Resident macrophages and specialized lymphatic sinus structures play a critical role in filtering lymph-borne substances, orchestrating a stepwise filtration process that prevents the entry of foreign substances into the bloodstream.

Primary and Secondary Lymphoid Organs

The lymphatic system is a group of organs, vessels and tissues that protect against infection and maintain fluid balance throughout the body. Lymphatic system organs include bone marrow, the thymus, and lymph nodes. The largest lymphoid organ is the spleen, which is involved in immune responses and in filtering the blood.

In the cortex of the thymus, developing T cells (thymocytes) come to distinguish between the body's own components ("self") and those substances foreign to the body ("nonself"). This occurs when thymocytes undergo positive selection, in which they are exposed to self molecules belonging to the major histocompatibility complex (MHC). Those cells capable of recognizing the body's MHC molecules are preserved, while those that cannot are destroyed. The thymocytes then move to the medulla of the thymus, where further differentiation occurs.

Lymphatic cells include macrophages, dendritic cells, and lymphocytes, as well as lymphatic organs such as the spleen and thymus.

Thoracic Duct and Cisterna Chyli

The lymphatic system conveys lymphatic fluid through a network of lymphatic channels, filters it through lymph nodes, and returns it to the bloodstream, where it is eventually eliminated. Nearly all body organs, regions, and systems have lymphatic channels that collect the various byproducts that require elimination. The thoracic duct is the largest lymphatic vessel in the body and represents the final common drainage pathway, returning lymph to the venous circulation at the junction of the left subclavian and internal jugular veins. The cisterna chyli is a dilated sac at the lower end of the thoracic duct where lymph from the lower body and intestines collects.

Physiological Functions

There are three primary functions of the lymphatic system: first is the maintenance of fluid balance, second is the facilitation of the absorption of dietary fats from the gastrointestinal tract to the bloodstream for metabolism or storage, and third is the enhancement and facilitation of the immune system.

1. Fluid Homeostasis

The lymphatic vessels reabsorb interstitial fluid from the periphery to return it to the intravascular space, which prevents fluid build-up in peripheral tissues. Of the fluid that leaves the capillaries, about 90 percent is returned directly. The 10 percent that does not return becomes part of the interstitial fluid that surrounds the tissue cells. Small protein molecules may leak through the capillary wall and increase the osmotic pressure of the interstitial fluid, further inhibiting the return of fluid into the capillaries, so that fluid tends to accumulate in the tissue spaces — making the lymphatic drainage of these proteins essential to normal physiology.

Lymph vessels return the capillary ultrafiltrate and escaped plasma proteins from most tissues back to the blood circulation. Working in partnership with the cardiovascular system, the lymphatics are responsible for maintaining tissue and plasma volume homeostasis.

2. Lipid Absorption and Transport

Intestinal lymphatics (lacteals) are responsible for most fat absorption, first documented by Gaspare Aselli in 1627, when the lymphatic system was discovered. Lymphatic vessels are found in nearly all tissues and have several important functions including transportation of fluids, plasma macromolecules, and cells back to the blood circulation. The lymphatics also form a major transport route for lipids absorbed from the intestinal tract and are a critical component of the immune system, transporting leucocytes and antigens from the tissues to the lymphoid organs.

3. Immune Surveillance and Defense

The lymphatics allow the immune system to function properly as they carry antigens to lymph nodes, and also carry immune cells such as macrophages to sites of infection to begin the immune process. Lymphatics have an important immune surveillance function, as they represent the principal route of transport from tissues for antigen and immune cells. As such, lymphatics are important for adaptive immunity.

The lymphatic system consists of initial capillaries, collecting vessels, trunks, and lymph nodes that transport lymph, a fluid rich in proteins, immune cells, lipids, and metabolic waste. Superficial and deep lymphatic networks are connected by perforating vessels that traverse fascial layers, maintaining tissue fluid balance and immune surveillance.

The lymphatics serve as the main pathways for the removal of inorganic material (e.g., silica and carbon) as well as dying and mutant cells. The lymphatic vasculature and nodal tissue is the preferred route for the metastatic spread of cancer. Accordingly, the lymphatic system may be important for defense against cancer by generating immune responses to malignant cell antigens.

Assessment of Lymphatic System Health

Assessment of the lymphatic system involves both clinical evaluation and specialized diagnostic tests. Aims of lymphedema evaluation include screening, diagnosis, individualization of treatment, and monitoring treatment response. Well-established assessment tools that have been integrated into lymphedema research and clinical management include history and physical examination, tape measure (TM), water displacement, perometry, and lymphoscintigraphy. A rapidly expanding collection of novel tools includes bioimpedance spectroscopy (BIS), tissue dielectric constant (TDC), three-dimensional (3D) camera, patient-reported outcome measures (PROMs), ultrasound, indocyanine green (ICG) lymphography, computed tomography (CT), and magnetic resonance imaging (MRI).

Lymphoscintigraphy

Lymphoscintigraphy is a special type of nuclear medicine imaging that provides pictures called scintigrams of the lymphatic system. It uses small amounts of radioactive material called radiotracers. Indirect radionuclide lymphoscintigraphy is a safe, non-invasive, and physiological method for the assessment of the limb lymphatic system, used for morphological studies and objective measurement of the peripheral lymphatic function necessary to assess lymphatic variation under therapy. This nuclear medicine test has essentially replaced the more complex procedure formerly used to assess the lymphatic system, as well as to determine the spread of cancer to lymph nodes.

Bioimpedance Spectroscopy

Bioimpedance spectroscopy is based on the theory that the level of opposition to the flow of electric current (impedance) through the body is inversely proportional to the volume of fluid in the tissue. In lymphedema, with the accumulation of excess interstitial fluid, tissue impedance decreases. Bioimpedance has been proposed as a diagnostic test for this condition. Bioimpedance spectroscopy and the tissue dielectric constant are non-invasive tools that quantify extracellular fluid volume and detect subclinical lymphedema with high sensitivity.

ICG Lymphography

ICG lymphography uses a specialized camera to visualize dye that is injected into the skin. The technology allows providers to see the actual lymphatic channels as they go up an arm or leg, as well as areas of blockage that cause spillage of dye into the surrounding tissues. It is one of the most commonly used imaging techniques in lymphatic surgery for diagnosing patients, staging, and planning surgeries.

Imaging: MRI and CT

Various imaging methods allow for the identification of fluid or assessment of the extent of lymphedema (with MRI); identification of anatomical abnormalities of the central lymphatics, including the presence or absence of the thoracic duct and variations in anatomy; and abnormal lymphatic flow, such as intercostal lymphatic flow and dermal backflow.

Factors That Support Normal Lymphatic Function

Physical Activity and Movement

Unlike the cardiovascular system, lymph is not actively pumped by the heart, but is forced through the vessels by the movements of the body, the contraction of skeletal muscles during body movements, and breathing. Clinical evidence supports the use of exercise in preserving lymphatic function. Self-manual lymph drainage, in combination with physical exercise, is beneficial for breast cancer patients in preventing postmastectomy scar formation, upper limb lymphedema, and shoulder joint dysfunction. A prospective randomized controlled study of 52 breast cancer patients found that a clinical and home-based, nurse-led physical activity program and simple lymphatic drainage significantly reduced the risk of developing breast cancer-related lymphedema compared to a control group.

Body Weight and Metabolic Health

Risk factors for lymphedema include obesity, limited mobility, and recurrent infections. A relationship between fat and lymphatics may exist well beyond the gut alone. Fat deposition is a defining clinical characteristic of lymphedema.

Compression and Manual Lymphatic Drainage

Management of established lymphedema focuses on early recognition, infection prevention, meticulous skin care, exercise, weight management, and compression garments. Effective care relies on patient education, self-management techniques such as manual lymphatic drainage, and a multidisciplinary approach.

Nutrients, Herbs, and Natural Ingredients

Research into nutrients which support the lymphatic system directly is limited. Research into nutrients that support the lymphatic system is currently very limited. It is logical that nutrients beneficial for supporting blood vessels might be similarly beneficial for the lymphatic vessels in maintaining tissue integrity and therefore optimal permeability and function. The following sections distinguish between traditional use and available scientific evidence.

Nutrients and Micronutrients

Vitamin C (Ascorbic Acid)

Role in Lymphatic Tissue: Vitamin C is needed for collagen formation, which forms part of the connective tissue in the outer layer of lymphatic vessels. The inner lining of lymph vessels is an epithelial lining, a one-cell thick layer, which in the lymphatic capillaries allows for fluid flow.

Scientific Evidence: Vitamin C (ascorbic acid) is implicated in many biological processes and has been proposed as a supplement for various conditions, including cancer. Research has examined its effects on the development and function of lymphocytes. The evidence base for vitamin C's direct effects on lymphatic vessel structure and drainage is primarily mechanistic (its requirement for collagen biosynthesis is well-established biochemistry); high-quality clinical trials specifically measuring lymphatic vessel function following vitamin C supplementation in healthy populations are lacking. Evidence is therefore indirect and preliminary for direct lymphatic applications.

Vitamin A, Vitamin D, and Zinc

Role in Lymphatic Tissue: Nutrients that support the epithelial layer of cells include vitamin A, vitamin D, and zinc. Deficiency in these nutrients is known to reduce epithelial integrity.

Scientific Evidence: The relationship between zinc, vitamin A, and vitamin D deficiency and immune cell function is well-established in nutritional science, with effects on lymphocyte proliferation documented in the broader immunological literature. However, clinical evidence specifically demonstrating that supplementation of these nutrients improves lymphatic vessel performance or lymphatic flow in humans without pre-existing deficiency is limited. Their relevance is primarily inferred from their known roles in maintaining mucosal and epithelial integrity.

Selenium

Scientific Evidence (strongest among micronutrients for lymphatic applications): Selenium has the most direct clinical evidence for an effect on lymphedema specifically. Between June 1996 and June 2001, a clinical trial treated 12 patients with edema of the arm and 36 patients with edema of the head-and-neck region with selenium for therapy-related lymphedema. The results suggested a short positive effect of sodium selenite on secondary head and neck lymphedema caused by radiotherapy alone or in combination with surgery.

A more rigorous study provides further detail: a randomized, double-blind, controlled trial was conducted on 26 participants with clinical stage II to III breast cancer-related lymphedema (BCRL). The control group (n = 12) and selenium group (n = 14) underwent five sessions of 0.9% saline and 500 μg sodium selenite (Selenase®) IV injections, respectively, within 2 weeks. At follow-up, 83.3% and 10.0% of the selenium and control groups, respectively, showed stage changes from III to II (p = 0.002). Extracellular water ratios were significantly reduced at 2 weeks and follow-up, only in the selenium group. Sodium selenite improved diagnostic stages of BCRL along with extracellular water ratios, although the beneficial effect might not be related to its antioxidant activity.

A systematic review of pharmacotherapy agents in lymphedema concluded that the majority of publications were clinical, and three authors conducted randomized, placebo-controlled, double-blinded clinical studies. Promising results were observed for the oral administration of selenium. Present data demonstrate that selenium can enhance the benefits of physical therapy in radiation-induced lymphedemas. The very low toxicity profile of selenium and its cost-effectiveness are further arguments for its use in lymphedema treatment.

Evidence strength: Preliminary to moderate. Studies are small (n = 12–48 typically), use varied doses and formulations (oral vs. IV), and populations are largely confined to radiation-treated cancer patients. Larger confirmatory RCTs are needed before broad clinical recommendations can be made.

Herbal and Botanical Ingredients

Cleavers (Galium aparine)

Traditional Use: Cleavers (Galium aparine) has a long history of use in traditional herbal medicine, particularly for supporting the lymphatic system. Herbalists have used cleavers as a "lymphatic tonic," claiming it helps stimulate lymph flow and reduce swollen glands. This traditional use is documented in historic European, North American, and Ayurvedic herbal texts. The plant is typically prepared as a tea, tincture, or topical wash for lymphatic complaints such as lymphedema, swollen lymph nodes, and as an adjunct for skin conditions linked to lymphatic stagnation.

Scientific Evidence: Scientific evidence to validate these traditional uses is limited. While cleavers contains bioactive compounds like iridoids, flavonoids, and coumarins, there is a lack of high-quality clinical studies directly demonstrating its effects on human lymphatic function. Some in vitro and animal studies suggest mild anti-inflammatory and diuretic properties, which could theoretically support lymphatic health, but these findings are preliminary. No robust human clinical trials specifically assessing cleavers' effect on lymphatic function have been published in peer-reviewed literature.

Evidence strength: Very weak — traditional use only; no quality human clinical trial evidence.

Red Clover (Trifolium pratense)

Traditional Use: Red clover (Trifolium pratense) has a long history of use in traditional herbal medicine, particularly in Western herbalism, where it is considered an "alterative" or "blood purifier." Historically, herbalists believed that alterative herbs support the lymphatic system by helping to clear waste products from the bloodstream and tissues, thus promoting healthy lymphatic function. Red clover was commonly included in traditional formulas aimed at supporting the lymphatic system, addressing conditions such as swollen glands, skin eruptions, and chronic inflammatory states thought to be related to lymphatic stagnation.

Scientific Evidence: From a scientific perspective, there is limited direct evidence to confirm that red clover specifically supports lymphatic health. Most modern research on red clover focuses on its isoflavones and potential benefits in menopause, cardiovascular health, and cancer prevention, rather than its effects on the lymphatic system. In summary, the use of red clover to support the lymphatic system is primarily justified by traditional use and historical precedent, rather than modern scientific validation.

Evidence strength: Very weak — traditional use only; no human clinical trials demonstrating direct lymphatic effects.

Echinacea (Echinacea purpurea and related species)

Traditional Use: Echinacea is a flowering plant native to central and eastern North America that has been used in herbal medicine for its potential to boost the immune system. Echinacea is better known for immune support during colds, but its relevance to the lymphatic system extends beyond fighting infections. It stimulates lymphocyte activity and has a traditional reputation for addressing swollen lymph nodes. The root is considered the most active part of the plant for lymphatic purposes.

Scientific Evidence: Echinacea's effects are most studied in the context of upper respiratory infections and immune modulation. A systematic review of 26 controlled clinical trials (18 randomized, 11 double-blind) found that existing controlled clinical trials indicate that preparations containing extracts of Echinacea can be efficacious immunomodulators. However, the evidence is still insufficient for clear therapeutic recommendations as to which preparation to use and which dose.

Regarding specific mechanistic actions relevant to the lymphatic immune interface: Echinacea extracts influence the immune system in a manner best described as adaptive immune modulation rather than pure immune stimulation. Echinacea significantly reduced expression of inflammatory cytokines TNF-α and IL-1β by up to 24% compared to baseline, and increased levels of the anti-inflammatory cytokine IL-10.

Evidence strength: Moderate for general immunomodulation; weak to absent for direct lymphatic drainage or lymphatic vessel effects specifically. The immunological actions of Echinacea indirectly involve lymphatic tissue (lymph nodes, lymphocytes) but clinical trials have not tested outcomes specific to the lymphatic system.

Astragalus (Astragalus membranaceus / Radix Astragali)

Traditional Use: Astragalus has been used medicinally and as food for centuries, especially in traditional Chinese medicine, where it is widely applied in immune modulation, antioxidant therapy, anti-inflammatory treatments, and antitumor applications.

Scientific Evidence: Recent studies show that Astragalus species are rich in bioactive compounds, such as polysaccharides, flavonoids, saponins, alkaloids, and simple phenolics, which demonstrate significant pharmacological effects including anti-inflammatory, antioxidant, immunomodulatory, and antitumor properties.

A study assessing the physiological response following in vivo administration of Astragalus membranaceus in human subjects found that a dose-dependent increase in monocytes, neutrophils, and lymphocytes was measured 8–12 hours after administration, and a dynamic change in the levels of circulating cytokines was observed, especially in interferon-γ and tumor necrosis factor-α. A PMC review of astragalus polysaccharides found that astragalus polysaccharides can promote the activities of macrophages, dendritic cells, natural killer cells, T lymphocytes, and B lymphocytes and induce the expression of a variety of cytokines and chemokines.

Evidence strength: Preliminary to moderate for immunomodulatory effects involving lymphocytes and immune cells that reside in lymphoid tissue. Direct evidence for effects on lymphatic vessel contractility, lymph flow, or lymphedema in clinical settings is lacking.

Quercetin (a flavonoid found in many plants)

Traditional Use: Quercetin is not used as a standalone traditional herb but is a biologically active flavonoid found in foods such as onions, apples, and berries, and in herbal preparations including Astragalus and many other plants.

Scientific Evidence: Quercetin is one of the most studied flavonoids in nutritional science, and its relevance to lymphatic health extends beyond its reputation for supporting a balanced immune environment. Mechanistically, quercetin helps regulate signaling markers in the bloodstream that can interfere with normal lymphatic vessel function when elevated. A 2019 meta-analysis of randomized controlled trials found that quercetin supplementation can significantly reduce C-reactive protein (CRP), particularly in individuals with underlying inflammatory or metabolic conditions, although effects on IL-6 were less consistent. In practical terms, quercetin helps lower overall inflammatory load, especially in people with existing metabolic stress. Still, its effects on specific inflammatory pathways are more variable.

Evidence strength: Preliminary. Anti-inflammatory effects are documented in RCTs, but no clinical trials have specifically tested quercetin's effect on lymphatic drainage, lymphatic vessel contractility, or clinically defined lymphedema.

Conditions and Diseases of the Lymphatic System

Dysfunction of the lymphatic system can lead to a variety of diseases and conditions, such as lymphedema, cancer metastasis, and inflammation. The lymphatic system clears away infection and keeps body fluids in balance. If it is not working properly, fluid builds in tissues and causes swelling, called lymphedema. Other lymphatic system problems can include infections, blockage, and cancer.

Lymphedema

Lymphedema is a chronic, progressive condition caused by impaired lymphatic drainage, leading to the abnormal accumulation of protein-rich lymphatic fluid in the interstitial tissues. When lymphatic transport capacity is exceeded, persistent edema triggers inflammation and progressive tissue remodeling, resulting in functional decline and long-term morbidity.

Lymphedema is classified as primary, due to congenital or genetic abnormalities in lymphatic development, or secondary, arising from acquired injury or obstruction. This condition most commonly occurs after cancer treatment, particularly when lymph nodes are removed or irradiated, but it can also arise from infections, injuries, or congenital abnormalities.

Primary Lymphedema: Primary lymphedema typically manifests through genetic mutations affecting lymphatic morphogenesis and is diagnosed via combined lymphoscintigraphy findings and molecular testing. The first gene identified as causative for human lymphedema was VEGFR3, in 1998. This gene was observed to be mutated in some cases of Milroy disease, a congenital-onset form of lymphedema with swelling of the feet and lower limbs. The gene for lymphedema-distichiasis syndrome was subsequently identified as the developmentally important transcription factor FOXC2. Lymphedema-distichiasis syndrome is a syndromic condition in which distichiasis (aberrant eyelashes originating from the meibomian glands) occurs at birth.

Secondary Lymphedema: Secondary lymphedema is an acquired disorder involving lymphatic system dysfunction that may result from many causes, including cancer, infection, trauma, or surgery. The treatment depends on the cause. Oncological and other surgeries may result in secondary lymphedema due to the removal or biopsy of lymph nodes or lymphatic vessels.

There is no absolute cure for lymphedema, but diagnosis and careful management can help to minimize complications. Management focuses on early recognition, infection prevention, meticulous skin care, exercise, weight management, and compression garments, relying on a multidisciplinary approach involving clinicians, certified lymphedema therapists, nurses, physical and occupational therapists, and mental health professionals.

Lymphoma

Lymphomas are cancers that arise from the cells of the lymphatic system. Lymphoma is cancer of the lymph nodes that occurs when lymphocytes grow and multiply uncontrollably. There are several different types, including Hodgkin's lymphoma and non-Hodgkin's lymphoma.

Lymphoma is a form of cancer in which masses of malignant T and/or B lymphocytes collect in lymph nodes, the spleen, the liver, and other tissues. The malignant leukocytes do not function properly, causing an increased risk for severe infection. Some types progress slowly and respond well to treatment, but others progress quickly and require aggressive treatment, without which they are rapidly fatal.

Hodgkin lymphoma can usually be cured if it is found and treated early. Non-Hodgkin lymphoma (NHL) is a diverse group of blood cancers that includes all types of lymphoma except Hodgkin's lymphoma. Non-Hodgkin lymphoma is much less predictable than Hodgkin lymphoma and is more likely to metastasize.

Lymphadenopathy (Swollen Lymph Nodes)

Common diseases and disorders of the lymphatic system include swollen lymph nodes (lymphadenopathy). Infection, inflammation and cancer cause swollen (enlarged) lymph nodes. Common infections that can cause enlarged lymph nodes include strep throat, mononucleosis, HIV, and infected skin wounds. Lymphadenitis refers to lymphadenopathy that is caused by an infection or inflammatory condition.

Lymphatic Filariasis

Lymphatic filariasis, or elephantiasis, is a very common mosquito-borne disorder caused by a parasite found in tropical and subtropical regions worldwide, including Africa, Asia, the Pacific, the Caribbean, and South America. This condition involves parasitic microscopic nematodes (roundworms) that infect the lymphatic system, rapidly multiply, and disrupt lymphatic function. Many infected individuals may have no outward symptoms, although the kidneys and lymphatic tissues may be damaged and dysfunctional. Symptomatic individuals may present with disfigurement due to severe lymphedema and elephantiasis (thickening of the skin, particularly the extremities). The parasite may also cause a hydrocele, an enlargement of the scrotum due to fluid accumulation, which may result from obstruction of the lymph nodes or vessels in the groin. Individuals presenting with symptoms have poorly draining lymphatics, often involving the extremities, resulting in huge extremities and marked disability.

Lymphangitis and Lymphangioma

Lymphangitis is an inflammation of the lymph vessels. Impaired lymphatic function predisposes to infection, which can clinically manifest as cellulitis/erysipelas, one of the most common medical conditions to present to hospital emergency departments.

Lymphangioma is a condition present from birth. It involves the presence of noncancerous, fluid-filled bumps (cysts) under the skin due to overgrown lymph vessels.

Intestinal Lymphangiectasia

Intestinal lymphangiectasia involves loss of lymph tissue in the small intestine, leading to loss of protein, gamma globulins, albumin, and lymphocytes. Systemic disorders of the lymphatics include intestinal lymphangiectasia, chylous ascites, pleural effusions, pericardial effusions, and pulmonary lymphangiectasia.

Noonan Syndrome and Associated Lymphatic Anomalies

Noonan syndrome is a genetic disorder characterized by unusual facial features, small stature, and cardiac anomalies. It affects approximately one in 1,000 to 2,500 live births. About 20% of patients develop lymphatic abnormalities. Noonan syndrome contributes to a large percentage of patients with nontraumatic lymphatic disorders. Manifestations include hydrops, chylothorax, pulmonary lymphangiectasia, mesenteric lymphangiectasia, and scrotal lymphangiectasia.

The Lymphatic System and Cancer Metastasis

The lymphatic vasculature and nodal tissue is the preferred route for the metastatic spread of cancer. Accordingly, the lymphatic system may be important for defense against cancer by generating immune responses to malignant cell antigens. The prevention of lymphatic entry and propagation of malignant metastasis would effectively render the cancer nonfatal.

New knowledge of lymphatic genes and molecular mechanisms has demonstrated that lymphatic dysfunction should no longer be considered a passive bystander in disease but rather an active player in many pathological processes and, therefore, a genuine target for future therapeutic developments.

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