Lymph nodes of the colon form four groups: the epicolic, paracolic, intermediate, and preterminal colic nodes. Epicolic nodes are minute nodules on the serosal surface of the colon. Paracolic nodes lie along the medial borders of the ascending, and descending colon as well as along the mesenteric borders of the transverse, and sigmoid colon. Intermediate nodes lie along the ileocolic, right colic, middle colic, left colic, sigmoid, and superior rectal arteries (15). Finally, preterminal nodes lie along the main trunks of the superior and inferior mesenteric arteries and drain Inhibitors,research,lifescience,medical into para-aortic nodes at the origin of these vessels. The drainage pattern of the PD-332991 lymphatic fluid from node to node begins with the nodes
closest to the colon and progresses from multiple
nodes through fewer and fewer nodes as the anastomoses between higher order nodes decrease. This process leads to a nomenclature of hierarchical designation for lymph nodes. Consequently, the para-aortic nodes are usually regarded as the highest nodes of the territory which they drain. Within the Inhibitors,research,lifescience,medical nodes at lower levels there is substantial redundancy in colonic coverage by lymphatic drainage possibly explaining the difficulty in determining sentinel lymph nodes as used in other organ resections (15). As such, a radical lymphadenectomy during resection for colorectal cancer requires the removal of the highest possible Inhibitors,research,lifescience,medical lymph nodes draining the area of the colon in which the tumor is located (15). Though Miscusi et al. showed in a small sample size that approximately 34 lymph nodes normally exist within the mesorectum (16), no studies have been performed that attempted to find the average number of lymph nodes present Inhibitors,research,lifescience,medical in the mesocolon. Figure 1 Diagram of the colon and lymphatic drainage. Lymph node Inhibitors,research,lifescience,medical key: right colic (dark green); superior mesenteric (aqua); middle colic (light green); left colic (dark red); sigmoid (purple); inferior mesenteric (orange). Paracolic lymph nodes (red and purple), … Colorectal carcinoma and anatomic sites There is a growing amount of evidence suggesting colon carcinomas of the right and left colon should
be considered distinct entities. A number of differences between the characteristics of right-sided colorectal carcinomas (RCC) and left-sided colorectal carcinomas (LCC) have been repeatedly demonstrated within the literature. Right-sided tumors are commonly Sitaxentan exophytic and present with complications of anemia or abdominal pain. In comparison, left-sided tumors more often cause obstructive symptoms. RCC tends to be: grossly more exophytic in appearance, of the mucinous histologic type and cytogenetically diploid, as well as demonstrate higher rates of microsatellite instability. LCCs, on the other hand, usually possess an infiltrative growth pattern, show chromosomal instability and are more often aneuploid (17). Such differences would suggest RCC and LCC might behave differently.