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Enhancing our understanding of lymphatic anatomy from the microscopic to the anatomical scale is essential to discern how the structure and function of the lymphatic system interacts with different tissues and organs within the body and contributes to health and disease. The knowledge of molecular aspects of the lymphatic network is fundamental to understand the mechanisms of disease progression and prevention. Recent advances in mapping components of the lymphatic system using state of the art single cell technologies, the identification of novel biomarkers, new clinical imaging efforts, and computational tools which attempt to identify connections between these diverse technologies hold the potential to catalyze new strategies to address lymphatic diseases such as lymphedema and lipedema. This manuscript summarizes current knowledge of the lymphatic system and identifies prevailing challenges and opportunities to advance the field of lymphatic research as discussed by the experts in the workshop.

Often regarded as the forgotten second circulatory system, the lymphatic system is critical in working with the venous and arterial system to maintain fluid equilibrium, circulate cells and signaling molecules in the immune system, and transport fat molecules and nutrients. When there is an alteration in the flow of lymphatic fluid, lymphedema is the result, usually manifesting as significant swelling of a particular region of the body with protein-rich fluid accumulation in the interstitial spaces. The result of this disease ranges from psychological disturbance to significant disability and morbidity, even leading to aggressive malignancy. The prevalence of lymphedema is in the hundreds of millions worldwide; however, it is routinely under-diagnosed and under-recognized as a disease, especially in the United States. Treatment rates for lymphedema are variable, ranging from low rates of treatment in non-cancer etiologies, to high treatment rates seen in breast cancer related etiologies. Furthermore, treatment modalities are equally notorious for being unsuccessful, either as a result of non-compliance or lack of efficacious therapeutic techniques, or a combination of both. There is no cure for lymphedema and treatment mainly focuses on minimizing limb swelling, maintaining functionality, and preventative treatments to reduce complications.

Lipedema is a relatively common, unrecognized connective tissue disorder. It affects about 11% of women across the globe. In lipedema, there is symmetrical abnormal deposition of fat especially in the lower extremities. Lipedema can be accompanied with pain, spider veins and easy bruising. Lipedema is rare in men. The disease is progressive in nature. Trigger points for lipedema appear to be puberty, pregnancy and menopause. The disease affects various aspects of the connective tissues like lymphatics, veins, skin, ligaments and even joints as it progresses. Oestrogen and progesterone abnormalities seem to have a role in the progression of the condition. Lipedema also appears to have a genetic predisposition. Lipedema is classified into 4 stages depending on the degree and type of abnormal fat deposition. The severe form can be confused with Dercum’s disease. Depending on the site of deposition of abnormal fat, lipedema is also classified into 5 different types. Lipedema is often confused to be obesity or lymphedema and treated accordingly. Treatments are based on the stages and types of lipedema. Lipedema is extremely difficult to manage with diet, exercises and bariatric surgery alone. All treatments are focused around improving the quality of life, improving physical abilities and appearances.

Lipedema is a chronic and progressive adipose tissue disorder, characterized by the painful and disproportionate increase of the subcutaneous fat in the lower and/or upper extremities. While distinct immune cell infiltration is a known hallmark of the disease, its role in the onset and development of lipedema remains unclear. To analyze the macrophage composition and involved signaling pathways, anatomically matched lipedema and control tissue samples were collected intra-operatively from gender- and BMI-matched patients, and the Stromal Vascular Fraction (SVF) was used for Cytometry by Time-of-Flight (CyTOF) and RNA sequencing. The phenotypic characterization of the immune component of lipedema versus control SVF using CyTOF revealed significantly increased numbers of CD163 macrophages. To gain further insight into this macrophage composition and molecular pathways, RNA sequencing of isolated CD11b+ cells was performed. The analysis suggested a significant modification of distinct gene ontology clusters in lipedema, including cytokine-mediated signaling activity, interleukin-1 receptor activity, extracellular matrix organization, and regulation of androgen receptor signaling. As distinct macrophage populations are known to affect adipose tissue differentiation and metabolism, we evaluated the effect of M2 to M1 macrophage polarization in lipedema using the selective PI3Kγ inhibitor IPI-549. Surprisingly, the differentiation of adipose tissue-derived stem cells with conditioned medium from IPI-549 treated SVF resulted in a significant decreased accumulation of lipids in lipedema versus control SVF. In conclusion, our results indicate that CD163+ macrophages are a critical component in lipedema and re-polarization of lipedema macrophages can normalize the differentiation of adipose-derived stem cells in vitro evaluated by the cellular lipid accumulation. These data open a new chapter in understanding lipedema pathophysiology and may indicate potential treatment options.

Lipoedema is an overlooked and often misdiagnosed condition, which mainly affects women. This review summarises the present knowledge of the condition. It is characterised by bilateral and symmetrical accumulation of subcutaneous adipose tissue mainly in the legs. Patients with lipoedema often display tenderness to palpation or spontaneous pain in the adipose tissue. Lipoedema is diagnosed based on the medical history and clinical findings. Treatment includes conservative and surgical options with the aim of relieving symptoms and increasing mobility, but there is a paucity of randomised controlled trials.

OBJECTIVE: Does short-term use of pneumatic compression devices (PCD) and off-the-shelf compression alleviate symptoms and improve quality of life in women with lipedema and secondary lipolymphedema? METHODS: Prospective, randomized controlled, industry-sponsored, proof-in-principle study comparing PCD plus conservative care (PCD+CC) to CC alone (control). Adult females with bilateral lipedema and secondary lymphedema were randomized to PCD+CC or CC. Outcome measures were lower limb and truncal circumferential measurements, bioimpedance, and quality-of-life, symptom, and pain intensity questionnaires. RESULTS: Both groups experienced improvements in leg circumference and bioimpedance with more improvement in the PCD+CC group than the CC group. Pain scores of the SF-36 survey and numerical rating scales were improved in the PCD+CC group. Wong-Baker Faces scores showed trends toward improvement in both groups. CONCLUSIONS: This proof-in-principle study supports conservative management with graduated compression and with or without PCD for improvement in leg circumference, bioimpedance measurements, and pain in patients with lipedema.

Edema of the lower extremities is always associated with a pathological condition that should be treated, especially in patients with chronic wounds. Because the underlying causes of edema can vary greatly and sometimes be complex, clinical and, if necessary, various diagnostic tests should also be performed. Often, a suspected clinical diagnosis can already be made after clinical inspection with testing of Stemmer's and Godet's signs. Sonographic examination should then be performed as the next diagnostic test. Although measurement techniques such as water plethysmography are currently considered gold standard for volume measurements, they are very complex and prone to error, so that they are rarely used in clinical routine today. In summary, it is recommended to perform a clinical examination, if possible in combination with sonography, for edema diagnosis. Especially at the beginning of the decongestion phase, regular circumferential measurements should be performed and documented. This documentation is of high relevance for evaluation of therapeutic success.

EXECUTIVE SUMMARY Nuclear medicine is an essential tool in the delivery of high-quality medical care, going beyond simple anatomical imaging to the use of physiological processes for both imaging and therapy. Nuclear medicine techniques were applied to the lymphatic system as early as the 1950s by Sherman et al. (1), using 198Au colloid (a beta emitter) as a therapeutic agent for lymph node metastasis. In the late 1960s and early 1970s, the ready availability of technetium-99m (99mTc) allowed more widespread lymphatic imaging (lymphoscintigraphy) with 99mTc colloid. In 1976, Ege (2) studied lymphatic flow in 848 patients, suggesting lymphoscintigraphy could demonstrate variable lymphatic drainage patterns, therefore allowing more accurate radiation therapy fields. In recent years, advances in radiopharmaceuticals and imaging technology have allowed more accurate localization of lymph nodes during lymphoscintigraphy and the development of the sentinel lymph node (SLN) concept. One of the first mentions of SLN was made in 1960 by Gould and Philben (3). They described a specific location of a node that drained the parotid gland. This node, located at the junction of the anterior and posterior facial veins, was described as the node most likely to contain metastasis. It was recommended that this node be investigated first before carrying out complete node dissection (3). The SLN concept was further explored by Cabanas (4) in 1977 when lymphangiography with contrast was used to identify a specific location for lymphatic drainage from the penis. Similar to what was described by Gould and Philben, Cabanas (4) felt that this 1 specific lymph node (located at the superficial epigastric vein by Cabanas for penile carcinoma) could be defined as the SLN for all patients. Individual variations demonstrated in the lymphatic channels and the location of the sentinel node since the initial investigations have confirmed that mapping of lymphatic drainage needs to be carried out for each patient undergoing SLN sampling. SLN identification can be done with optical agents, such as isosulfan or methylene blue, as well as with radiotracers and fluorescent tracers. Localization of the SLN(s) with these techniques in individual patients has allowed a more focused investigation of nodal drainage from a primary tumor site, preventing the morbidity and mortality of complete node bed dissection in patients with no clinical evidence of tumor in the regional nodal basin (5). One difficulty with reviewing the literature describing lymphoscintigraphy is the variety of tracers in use around the world and throughout the history of lymphoscintigraphy. Smaller particles tend to move through the lymphatics more quickly. Some tracers are more likely to stop at the first node they encounter, while others are more likely to move through the lymphatic system more readily, demonstrating channels, node beds, and central lymphatic structures. The tracer used depends on the clinical indication (e.g., sentinel node scintigraphy, lymphedema, or lymphatic vessel integrity), as well as availability and local regulations. In the United States, there are only 2 tracers generally available for clinical use: 99mTc sulfur colloid and 99mTc tilmanocept. In addition, injection techniques, imaging protocols, and camera technology can vary substantially, making comparisons between studies challenging. A discussion of these technical differences is beyond the scope of this document. These appropriate use criteria (AUC) have been developed to describe the appropriate use of radiopharmaceuticals for lymphoscintigraphy in SLN mapping and lymphedema. It is hoped that through these recommendations, nuclear medicine lymphatic imaging techniques will be used to benefit patients in the most cost-effective manner. Representatives from the Society of Nuclear Medicine and Molecular Imaging (SNMMI), the Society for Vascular Medicine (SVM), the Australia and New Zealand Society of Nuclear Medicine (ANZSNM), the American College of Radiology (ACR), the Society of Surgical Oncology (SSO), the European Association of Nuclear Medicine (EANM), the American Head and Neck Society (AHNS), the American Society of Clinical Oncology (ASCO), the American Society of Breast Surgeons (ASBrS), the American College of Nuclear Medicine (ACNM), and the American College of Surgeons (ACS) assembled as an autonomous workgroup to develop these AUC. This process was performed in accordance with the Protecting Access to Medicare Act of 2014 (6). This legislation requires that all referring physicians consult AUC by using a clinical decision support mechanism before ordering any advanced diagnostic imaging services. Such services are defined as diagnostic magnetic resonance imaging (MRI), computed tomography (CT), and nuclear medicine procedures, including positron emission tomography (PET) and others, as specified by the Secretary of Health and Human Services in consultation with physician specialty organizations and other stakeholders (3). Lymphoscintigraphy usually causes trivial radiation exposures for the patient, the surgeon, and the staff handling any specimens that may contain radioactivity. Local regulations that address the handling of radiopharmaceuticals and exposure of the public should always be followed. Radiation exposures are also trivial for pregnant patients and infants exposed to someone who has been injected with lymphoscintigraphic agents labeled with 99mTc. The amount of radiopharmaceutical transferred from the interstitium into the blood and from the blood to the milk is very low. However, when performing an SLN procedure for breast cancer, it seems prudent to recommend the interruption of direct breastfeeding for 24 hours after administration of the radiopharmaceutical. There is a potential for more fetal or infant exposure if the radioisotope dissociates from the radiopharmaceutical; however, exposures will remain very small and likely of no consequence. The rapid decay of 99mTc (6-hour half-life) also allows for rapid return of radiation exposures to background levels within a short time. More detailed information can be found in the document “Advisory Committee on Medical Uses of Isotopes (ACMUI) Sub-Committee on Nursing Mother Guidelines for the Medical Administration of Radioactive Materials” (https://www.nrc.gov/docs/ML1803/ML18033B034.pdf).

Socio-economic position is a well-established driver of health status in the United Kingdom. However, less is known about the reverse relationship — the effect health conditions have on socio-economic position and social mobility. The purpose of this qualitative study was to explore individual experiences and perceptions of the relationship between ill-health and social mobility amongst people with long-term physical health conditions. Structured, in-depth interviews or focus group discussions were conducted with 37 people with long-term physical health conditions (including asthma, cancer, diabetes, heart disease, back pain, arthritis and lipoedema) between November 2019 and January 2020. Participants were asked about the impact of physical health on their career, education, and social life. Factors affecting their ability to cope with their condition were also explored. Participants reported their conditions had been a barrier to upward, and a facilitator of downward social mobility. Physical health conditions were commonly reported to have affected the participants’ educational attainment, choice of occupation, financial stability, and retirement age. Participants also described a lack of understanding from employers about their conditions, with some experiencing instances of discrimination. Factors that reduced the extent to which their condition affects social mobility included, a feeling of control over their condition, support from their employers and knowledge of the available support systems. Individual experience, psychological make-up, and early-life experience also mediated the impact. Participants described clear regional differences in terms of access to services. Advice and support services were often filled by charitable organisations. In conclusion, physical ill-health was reported to have a substantial downward impact on social mobility; by negatively impacting a person's education, choice of occupation and earning ability. Key changes that may enable people to better manage their condition and its impact on social mobility include, improved training of and support from employers and better and consistent access to multi-disciplinary support services from the health and social care system.

Lipedema is a pathology of the adipose tissue, in evident female prevalence, diagnosed clinically and still of not well-defined etiopathogenesis. Indeed, an estrogen-related component is present, and an inflammatory state and a condition of edema are present in most cases; even pain seems to be a recurring feature, and insulin resistance is also often associated with lipedema. The therapeutic approach is finally becoming holistic. Therefore, with surgery, physiotherapy, and elastic compression therapy, the nutritional aspect of food supplementation is gaining much value. The objective of the present work is to consider the nutritional supplements that could be useful to manage this condition, underlining that, at the moment, the specific literature is practically non-existent. The most promising supplements seem to be omega 3 fish oil, polyphenols, and vitamin C, but the need for studies in this sector is urgent.

Lipedema is an adipofascial disorder that almost exclusively affects women. Lipedema leads to chronic pain, swelling, and other discomforts due to the bilateral and asymmetrical expansion of subcutaneous adipose tissue. Although various distinctive morphological characteristics, such as the hyperproliferation of fat cells, fibrosis, and inflammation, have been characterized in the progression of lipedema, the mechanisms underlying these changes have not yet been fully investigated. In addition, it is challenging to reduce the excessive fat in lipedema patients using conventional weight-loss techniques, such as lifestyle (diet and exercise) changes, bariatric surgery, and pharmacological interventions. Therefore, lipedema patients also go through additional psychosocial distress in the absence of permanent treatment. Research to understand the pathology of lipedema is still in its infancy, but promising markers derived from exosome, cytokine, lipidomic, and metabolomic profiling studies suggest a condition distinct from obesity and lymphedema. Although genetics seems to be a substantial cause of lipedema, due to the small number of patients involved in such studies, the extrapolation of data at a broader scale is challenging. With the current lack of etiology-guided treatments for lipedema, the discovery of new promising biomarkers could provide potential solutions to combat this complex disease. This review aims to address the morphological phenotype of lipedema fat, as well as its unclear pathophysiology, with a primary emphasis on excessive interstitial fluid, extracellular matrix remodeling, and lymphatic and vasculature dysfunction. The potential mechanisms, genetic implications, and proposed biomarkers for lipedema are further discussed in detail. Finally, we mention the challenges related to lipedema and emphasize the prospects of technological interventions to benefit the lipedema community in the future.

Lipoedema is a chronic disease in adipose tissue that almost exclusively affects women during periods of hormonal alterations. Its main symptoms include an abnormal accumulation of subcutaneous fat in the buttock, hips, and legs, which is associated with pain, swelling, and easy bruising. Herein, a grading in three stages is used to determine disease progression. Problematically, lipoedema manifestations are often confused with lifestyle-induced obesity, which is why the various health problems among affected women often remain unrecognized. Overall, research on lipoedema is scarce. As such, this study examined the health, health-related quality of life (HRQOL), and sense of coherence (SOC) among women with lipoedema.

Lipedema is a common disorder characterized by excessive deposition of subcutaneous adipose tissue (SAT) in the legs, hips, and buttocks, mainly occurring in adult women. Although it appears to be heritable, no specific genes have yet been identified. To identify potential genetic risk factors for lipedema, we used bioelectrical impedance analysis and anthropometric data from the UK Biobank to identify women with and without a lipedema phenotype. Specifically, we identified women with both a high percentage of fat in the lower limbs and a relatively small waist, adjusting for hip circumference. We performed a genome-wide association study (GWAS) for this phenotype, and performed multiple sensitivity GWAS. In an independent case/control study of lipedema based on strict clinical criteria, we attempted to replicate our top hits. We identified 18 significant loci (p < 5 × 10−9), several of which have previously been identified in GWAS of waist-to-hip ratio with larger effects in women. Two loci (VEGFA and GRB14-COBLL1) were significantly associated with lipedema in the independent replication study. Follow-up analyses suggest an enrichment of genes expressed in blood vessels and adipose tissue, among other tissues. Our findings provide a starting point towards better understanding the genetic and physiological basis of lipedema.

BackgroundThere are both conservative and surgical treatment options for Lipohyperplasia dolorosa (LiDo). A procedure that has been established since 1997 is the surgical treatment through Lymphological Liposculpture according to Cornely™.AimAfter extensive suctioning of the extremities, an extensive subcutaneous wound cavity with a trabecular connective tissue scaffold remains. Nevertheless, surgery-related complications are rare. Postoperative management and administration of antibiotics and antithrombotics are reviewed. The therapies for complications are presented in detail.Materials and methodsRetrospectively, the frequencies of adverse events in 1400 LiDo surgeries in 2020 were evaluated. The mean age of the patients was 47.81 years (range 16–78 years). Symmetrically, 504 outer legs (outer half of the limb [BO]), 504 inner legs (inner half of the limb [BI]), and 392 arms [A] were surgically treated.ResultsRelevant adverse events rarely occurred: infections (1.79%), seromas (0.79%), erysipelas (0.28%), necrosis (0.14%) and deep vein thrombosis (0.07).DiscussionWe were able to reduce the rate of postoperative complications to 3.07% in the Lymphological Liposculpture™ regime for the surgical treatment of LiDo. In their meta-analysis on liposuction, Kanapathy et al. reported an overall incidence of major surgical complications of 3.35%. The overall incidence of minor surgical complications was 11.62%, with seroma (5.51%) being the most common minor complication [26]. Kruppa et al. report that the liposuction procedure including fat removal for esthetic reasons has a complication rate of 9.5%. Wound infections with 4.5% and the formation of erysipelas with 4% are clearly in the foreground [20].

In this study an analysis of identified ICG lymphography features of the superficial lymphatics of the lower extremity was undertaken [Table 2.2]. The absence or presence and extent of the superficial lymphatics in the limb with LLLE was assessed to identify if any of these features or combination of features were significantly associated with particular diagnostic groups of primary or secondary cancer related or secondary non-cancer related LLLE. ICG lymphography studies undertaken by the researcher (submitted for publication) had identified two compensatory lymph drainage regions, the contralateral inguinal and axillo-inguinal nodal regions, associated with secondary cancer related LLLE which were not seen or very rarely seen in clinically diagnosed primary LLLE and less so in secondary non-cancer related LLLE. Conversely, retrograde flow in lymph vessels demonstrated during the ICG lymphography procedure was not seen in secondary cancer related LLLE. These observations provided a background rationale to exploring the diagnostic capacity of ICG lymphography in LLLE. One purpose of this study was to explore the feasibility of using ICG lymphography features as a diagnostic tool. It was hoped that identified ICG lymphographic features would allow the individual presenting with persistent leg swelling of unknown causation to be able to be advised that their condition is most likely a secondary non cancer related LLLE rather than an adult onset primary LE and therefore be possibly less likely to progress or deteriorate. This may potentially provide better prognostic information and improve individualised therapeutic plans of management and support compliance (Pigott, 2021). The aim of Part A of this study was to identify the prevalence and characteristics of ICG lymphography features of the lymph vessels, position and extent of DBF and drainage patterns. In addition, Part B of this study was to explore whether using the ALERT standardised ICG lymphography technique and a structured analysis of ICG lymphography features could be translated into a simple score to distinguish the ICG pattern of adult onset primary LLLE from secondary non-cancer related LLLE.

INTRODUCTION: Lipedema is a poorly known condition. Diagnosis is based almost exclusively on clinical criteria, which may be subjective and not always reliable. This study aimed to investigate regional body composition (BC) by dual-energy X-ray absorptiometry (DXA) in patients with lipedema and healthy controls and to determine cut-off values of fat mass (FM) indices to provide an additional tool for the diagnosis and staging of this condition. METHODS: This study is a single-center case-control study performed at Lausanne University Hospital, Switzerland. Women with clinically diagnosed lipedema underwent regional BC assessment by DXA. The control group without clinical lipedema was matched for age and body mass index (BMI) at a ratio of 1:2 and underwent similar examination. Regional FM (legs, arms, legs and arms, trunk, android and gynoid FM) was measured in (kg) and divided by FM index (FMI) (kg/m2) and total FM (kg). The trunk/legs and android/gynoid ratios were calculated. For all indices of FM distribution showing a significant difference between cases and controls, we defined the receiver operating characteristic (ROC) curves, calculating the area under the curve (AUC), sensitivity, specificity, and Youden's index. Types and stages of lipedema were compared in terms of FM indices. Correlation analyses between all FM distribution indices and lipedema stages were performed. RESULTS: We included 222 women (74 with lipedema and 148 controls). Overall, the mean age was 41 years (standard deviation [SD] 11), and mean BMI was 30.9 kg/m2 (SD 7.6). A statistically significant difference was observed for all DXA-derived indices of FM distribution between groups, except for arm FM indices. The ROC curve analysis of leg FM/total FM, as a potential indicator of lipedema, resulted in an AUC of 0.90 (95% confidence interval 0.86-0.94). According to Youden's index, optimal cut-off value identifying lipedema was 0.384. Sensitivity and specificity were 0.95 and 0.73, respectively. We found no significant differences between lipedema types and stages in terms of FM indices, nor significant correlations between the latter and lipedema stages. DISCUSSION/CONCLUSION: BC assessment by DXA, and particularly calculation of the leg FM/total FM index, is a simple tool that may help clinicians rule out lipedema in doubtful cases.