Defining lymphatic drainage of the liver segments in man

The role of the liver lymphatic system in liver disease and malignancy has not
been extensively studied. In cirrhosis, fibrosis, and other abnormalities of
liver architecture, portal lymph flow is increased (Ohtani, 2008). Liver
lymphangiogenesis occurs in cirrhosis but also in hepatocellular carcinoma
(HCC) and lymphatics are abundant in the periphery of metastatic liver tumors
(Mouta Careira, 2001). The lymphangiogenic growth factor vascular endothelial
growth factor (VEGF)-C is present in the human liver (Joory, 2006) and VEGF-C
overexpression is associated with lymph node metastasis and poor survival in
HCC (Xiang, 2009). Clinically, (hepatic pedicular) lymph node metastasis is a
common phenomenon in colorectal liver metastasis that is present in 15-28% of
patients undergoing resection (Adam, 2011; Beckurts, 1997; Laurent, 2004,
Viana, 2009). The presence of lymph node metastasis in these patients
significantly worsens their prognosis to a 5-year overall survival to 5-22%
(Adam, 2008; Adam, 2011; Beckurts, 1997; Laurent, 2004), which compares
unfavorably even to patients with lung metastases. Pathologically, the presence
of intralymphatic tumor cells in colorectal liver metastasis correlates with
(hepatic pedicular) lymph node metastasis (Korita, 2007). In addition,
colorectal liver metastases contain lymphatic vessels (Schoppmann, 2011; Hadj,
2012). This evidence suggests that intrahepatic lymphatic spread may contribute
to onward dissemination of colorectal liver metastasis and that this phenomenon
carries an unfavorable prognosis.

Our preliminary data identify a subgroup of colorectal liver metastasis
patients specifically at risk for hepatic-lymphatic dissemination.

In the past 15 years, one of the major reasearch subjects of the Department of
Oncological Surgery (Borel Rinkes/Kranenburg Group) in the UMC Utrecht is the
biology of colorectal metastases in the liver. Novel preliminary data identify
1) a lymphangiogenesis gene set is associated with a poorly-differentiated,
stem-cell like colon cancer phenotype that carries a poor prognosis, and 2) a
subgroup of colorectal liver metastases that carries a poor prognosis expresses
high levels of the lymphangiogenesis gene set. These data are currently under
further investigation. They suggest that a specific patient subgroup with
colorectal liver metastasis may benefit from therapy targeting the molecular
pathways involved in lymphatic dissemination and that these patients, when
undergoing partial hepatectomy for their disease, may benefit from additional
lymph node dissection. To further design such translational studies, functional
anatomy of the liver lymphatic system (to which lymphatics/lymph nodes does a
specific liver segment drain?) needs to be elucidated.

Knowledge about the functional anatomy of the liver lymphatic system is
necessary for clinical translation of our experimental data but is currently
lacking. The liver has an extensive lymphatic system and produces a very large
volume of lymph, estimated at 25-50% of lymph flowing through the thoracic duct
(Barrowman, 1991). Lymphatic vessels are found in the liver capsule, but 80% or
more of hepatic lymph drains into portal lymphatic vessels (Ohtani, 2008). The
origin of hepatic lymph is mainly from both the portal circulation and the
arterial peribiliary plexuses (Ohtani, 2008). Hepatic lymph is drained to
several extrahepatic lymph node groups, including the hilar and
subdiaphragmatic (Moore, 2006). All these data stem from older post-mortem
anatomical studies (Moore, Ohtani). In addition, one study performed
intraoperative lymphangiography in patients undergoing partial hepatectomy and
found blue stained perihepatic lymphatics in 11 out of 13 patients undergoing
the procedure (Kane, 2002). Importantly, the distribution of intrahepatic and
extrahepatic drainage relative to liver segmental anatomy has not
systematically been described.

Therefore, we aim to define the pattern of lymphatic drainage from each of the
liver segments, using standard lymphangiography during planned partial liver
resection, thereby creating a *drainage map* of the human liver.

Lymphangiography and draining lymph node identification is performed by
peroperative injection of blue dye in the parenchyma of a liver segment to be
resected (one segment per patient). Subsequent immunohistological analysis is
performed on resected tissue specimen biopsies.

Upon laparotomy and assessment of resectability for a planned partial
hepatectomy, blue dye is injected in the parenchyma of (one of the) liver
segment(s) te be resected by the one of the hepato-pancreato-biliary surgeons
involved in this study. After further mobilization of the liver as needed for
resection, the lymphatics and lymph nodes draining the liver (hilar,
periportal, subdiaphragmatic) are inspected for blue dye and digitally recorded.

After surgery, a tumor tissue fragment from the segment injected as well as
from other segments will be collected at the Department of Pathology.
Collection of liver tissue fragments will only be performed when it will not
jeopardize diagnostics. The infrastructure between the department of Pathology
and Surgical Oncology already exist for other studies (such as the *Collection
of blood and tissue samples from patients subjected to liver surgery for liver
malignancies* * METC protocol ID 09-145). The liver tissue samples will then be
used for immunohistochemistry by the other executing researchers.

Partial hepatectomy is a common procedure world-wide for primary and secondary
liver malignancy. Hilar lymph node dissection is commonly performed as a
staging procedure in primary liver cancer and preclinical evidence suggests
that it may be of benefit in colorectal liver metastasis. However, the
functional anatomy of the liver lymphatic system and its draining lymphatic
vessels and lymph nodes remains poorly defined. To be able to perform future
systematic clinical studies on liver lymph node dissection, we aim to delineate
the lympatics and lymph nodes that drain each of the liver segments. Given that
this observational study involves a single invasive measurement during a
planned laparotomy under general anesthesia, there is no direct clinical
benefit for an individual patient and that the burden and risks associated with
participation are very low.