Introduction
Lymph vessels under normal conditions
Macroscopic anatomy and organization
Physiological roles
Interstitial fluid balance
Lymph transport
Key points: |
• Lymphatic vessels are widely distributed throughout the body. They can be divided into absorbing, non-contracting initial lymphatics and contractile collecting lymphatics. |
• Lymph flow is not a passive process, but results from spontaneous contractions generated in functional units called lymphangions |
In vivo imaging of lymphatic vessels
Lymphoscintigraphy
Magnetic resonance lymphangiography
Near infrared fluorescence imaging
Key points:
|
• Lymphoscintigraphy is the gold standard for investigating the lymphatic vasculature in humans. The techniques allow quantification of lymph transport and visualization of the major lymphatic vessels. |
• Magnetic resonance lymphangiography and near infrared fluorescence imaging is emerging as new techniques due to superior spatial and temporal resolution. |
Primary lymphedema
Secondary lymphedema
Key points:
|
• Primary lymphedema is caused by a failure of the development of the lymphatic system whereas secondary lymphedema is the result of an external stimulus, e.g. parasitic or cancer (metastasis or induced by treatment). |
• Advance in genetics have so far identified nine causal genes of primary lymphedema and has helped refine the classification of primary lymphedema, which now is based on clinical genotyping and phenotyping. |
Microscopic imaging of lymphatic vessels and histopathology of lymphatics
Immunohistochemical markers for lymphatic endothelium
Lymphatic markers | Podoplanin | LYVE-1 | Prox-1 | VEGFR-3 | |
---|---|---|---|---|---|
Lymphatic vessels | Capillary | ++ | ++ | ++ | ++ |
Collecting vessel | ++ | ++ | + | +/++ | |
Blood vessels | Artery | - | - | - | - |
Capillary | - | - | - | + | |
Vein | + | - | - | - | |
Hepatic sinus | + | + | - | + | |
Embryonic development | +/++ | +/++ | ++ | +/++ | |
Postnatal development | ++ | ++ | ++ | ++ |
Key points
|
• CD31 is the most sensitive and specific pan-endothelial marker. |
• Most important specific lymphatic endothelium markers are podoplanin (D2-40), Prox-1, and LYVE-1. |
• The use of the panel of one pan endothelial marker and two lymphatic markers is recommended for proper identification of lymphatic vessels. |
Lymphatic vessels: inflammation
Lymphatic vessels: transplantation
Lymphatic vessels: atherosclerosis, lipid metabolism, obesity and hypertension
Lymphatic differentiation in tumours and tumour-like lesions
Current classification
Vascular tumours with lymphatic differentiation
Name | Biological behavior according to ISSVAa 2015 [55] |
---|---|
Primary lymphoedema/lymphatic malformation | Congenital malformation. Isolated or in combination with other vascular or nonvascular malformations or genetic syndromes |
Tufted angioma | Benign tumor of skin. Partial lymphatic differentiationb
|
Spindle cell angioma | Provisionally unclassified. Probably vascular malformation with partial lymphatic differentiation |
Verrucous angioma | Provisionally unclassified; probably congenital malformation with partial lymphatic |
Angiokeratoma | Provisionally unclassified vascular anomaly. Partial lymphatic differentiation |
dMLT/CATc
| Provisionally unclassified lesion. |
Kaposiform hemangioendothelioma | Locally aggressive tumor. Extends into deep tissues; resembles tufted angioma |
PILAd
| Borderline malignant tumour |
Kaposi sarcoma | Borderline malignant tumour |
Lymphangiosarcoma | Malignant. Variable expression patterns with lymphatic markers |
Kaposiform lymphangiomatosis | Provisionally unclassified vascular lesion |
Key points
|
• Many lesions that were previously designated as ‘lymphangiomas’ are in fact lymphatic malformations, being mostly congenital in nature |
• Specific lymphatic endothelium antibodies identify (partial) lymphatic differentiation in a still increasing number of vascular tumours |
• Occurrence of blood-filled spaces, haemorrhages or hobnail appearance of endothelium does not rule out the diagnosis of a lymphatic lesion |
Lymphovascular invasion: patterns and diagnosis
Authors, setting and date of study (reference number) | Number and type of biopsy | Principle findings | Comments |
---|---|---|---|
Alexander-Sefre et al. London, UK 2003 [72] | 108 patients with stage 1 endometrial adenocarcinoma | Substantial increase in the detection of vascular invasion with pan-cytokeratin and CD31 immunohistochemistry (from 21 to 58 cases). No distinction between blood and lymphatic vessels | Vascular invasion has been underestimated in early endometrial adenocarcinoma |
Vass et al. Glasgow, UK 2004 [73] | 75 Colonic adenocarcinomas | Elastin staining increased detection of venous invasion from 18 to 32 cases for extramural invasion and from 8 to 30 cases for intramural invasion | Elastic staining should be part of standard protocols |
Pawlik et al. China, France, Japan, USA 2006 [74] | Multinational registry of 1073 resections for hepatocellular carcinoma | 41 % of tumours >5 cm had LBVI in comparison with 27 % <5 cm. Multicentricity, histological grade and high AFP levels also associated with LBVI | No comments on histological methods for identifying LBVI |
Chen et al. South Australia 2010 [75] | 110 Whipple’s resections for pancreatic carcinoma between 1998 and 2008 | 5 year survival 77 % in patients negative for both LBVI and perineurial invasion but only 15 % in patients positive for both | Poor differentiation, size >3 cm and nodal involvement also poor prognostic features |
Storr et al. Nottingham, UK 2012 [76] | 202 cutaneous melanomas | Lymphatic invasion more common than venous invasion (27 vs 4 %). Immunohistochemistry with CD34 and D2-40 increases detection rate of blood vessel and lymphatic invasion. | Lymphatic invasion is associated with adverse factors but lymphatic characteristics do not predict outcome |
Kirsch et al. Canada 2013 [77] | Sections of 40 colorectal carcinomas circulated to specialist and non-specialist GI pathologists | GI pathologists detected venous invasion more frequently than non-GI with both H&E and Movat’s stain. Detection of venous invasion was >2 fold higher with Movat’s stain (46 vs 20 %) | Venous invasion is under-detected with H&E, even by specialist pathologists |
Gujam et al. Glasgow, UK 2014 [78] | Review of 59 reports of 62514 patients with breast carcinoma | 19/21 studies demonstrated lymphatic vessel invasion predicted poorer prognosis. Improvement of lymphatic detection using immunohistochemistry | Guidelines for the use of immunohistochemistry in mammary carcinoma should be followed |
Castonguay et al. Canada 2014 [79] | 103 oesophageal adenocarcinoma resections | Venous invasion detected in 8 cases with H&E but in an additional 66 cases with Movat’s pentachrome | Venous invasion, stage, size and grade prognostically significant on univariate analysis |
Detection of lymphovascular invasion in surgical resections
Techniques for detection of lymphatic and venous invasion
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Appropriate sampling of tumours and adjacent tissuesFew studies have specifically addressed dissection techniques for the enhanced detection of LBVI. The convention that malignant tumours should be sampled in three blocks is outdated and we advocate a minimum of five. Sternberg and colleagues dissected blocks perpendicular and tangential to tumours, blocks taken across the mesentery and around major blood vessels [91]. The authors found that LBVI was most often detected in perpendicular blocks but in some cases, it was only identified in the tangential blocks. Further studies of dissection techniques and the number of blocks that should be sampled would be valuable.
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“What to look for”—recognition of the particular histological features of vascular invasionThe multicentre Canadian study of Kirsch et al. described two important histological signs that suggest LBVI in colorectal carcinoma, although no distinction was made between lymphatic and blood vessels. Veins and arteries are closely related to each other but this is especially true in the bowel wall. The so-called protruding tongue sign is a rounded protrusion of carcinoma extending towards the extramural space at the tumour edge. This suggests venous invasion, especially if the deposit is close to a small artery. In the ‘lone artery’ or ‘orphan arteriole’ sign, an often elongated tumour deposit is seen next to a normal extramural artery. This, in fact, is an obliterated vein twinned with the artery [77]. Whether this also applies to lymph vessels is not known.
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Routine use of special stains, especially elastic tissue stains and vascular immunohistochemistry.Small- and medium-sized lymphatics contain a network of elastic tissue although less in abundance than in veins. In contrast to arteries, this is not arranged as distinct internal and external lamellae but as an irregular network. Small lymphatic invasion can be identified with immunomarkers but larger vessel invasion might be indistinguishable from venous as the endothelium is obliterated by most carcinomas. Elastin can form tumour within nests of malignant cells and must not be mistaken as evidence of vascular invasion. In this context, Kojima et al. suggested that venous invasion should only be diagnosed when a tumour deposit has 50 % of its circumference surrounded by elastin or D2-40 [90]. Remnants of vascular media of larger veins or lymph vessels can sometimes be visualized adjacent to tumour deposits with the use of smooth muscle actin immunostaining. Figure 6 displays intratumoral invasion of small vessels by immunostaining for CD31 and D2-40.×
Key points
|
• LI detection in breast carcinomas is especially important in patients with operable breast cancer without lymph node involvement. |
• Defined criteria of vascular invasion need to be used alongside special stains to detect vascular invasion in colorectal carcinoma. |
• Vascular antibodies, particularly the lymphatic marker D2-40, improve detection of LI in malignant melanoma. |