Anatomy of the transverse colon revisited with respect to complete mesocolic excision and possible pathways of aberrant lymphatic tumor spread

Although lymph node metastases to pancreatic and gastroepiploic lymph node stations in transverse colon cancer have been described, the mode of lymphatic spread in this area remains unclear. This study was undertaken to describe possible pathways of aberrant lymphatic spread in the complex anatomic area of the proximal superior mesenteric artery and vein, the greater omentum, and the lower pancreatic border. Abdominal specimens obtained from four cadaveric donors were dissected according to the principles of complete mesocolic excision. The vascular architecture of the transverse colon was scrutinized in search of possible pathways of lymphatic spread to the pancreatic and gastroepiploic lymph nodes. Vascular connections between the transverse colon and the greater omentum at the level of both the hepatic and the splenic flexures could be identified. In addition, small vessels running from the transverse mesocolon to the lower pancreatic border in the area between the middle colic artery and the inferior mesenteric vein were demonstrated. Moreover, venous tributaries to the gastrocolic trunk could be exposed to highlight its surgical importance as a guiding structure for complete mesocolic excision. The technical feasibility to clearly separate embryologic compartments by predefined tissue planes in complete mesocolic excision was confirmed. However, the vicinity of all three endodermal intestinal segments (foregut, midgut, and hindgut) obviously gives way to vascular connections that might serve as potential pathways for lymphatic metastatic spread of transverse colon cancer.