Tuesday, August 21, 2012

Lymph Node Stations for Pelvic Tumors

Most pelvic visceral tumors metastasize via lymphatics. Metastases to regional lymph nodes is consider N stage in the TNM classification system while spread to nonregional lymph nodes is considered M stage disease (distant metastases). Since upstaging influences prognosis and clinical management, knowledge of the pelvic nodal anatomy is important in evaluation of cross sectional imaging. 

The following groups of pelvic lymph nodes should be considered:
1. Common iliac lymph nodes: between the aortic bifurcation and the common iliac vessel bifurcation.
  • Medial, lateral, and lumbosacral subdivisions
    • lumbosacral subdivision refers to lymph nodes in the lumbosacral fossa (triangular region bounded by common iliac vessels medially, psoas muscle laterally, and lower lumbar/upper sacral vertebral bodies posteriorly)
2. External iliac lymph nodes: between the common iliac vessel bifurcation and the inguinal ligament
  • Medial and lateral subdivisions
    • obturator nodes are considered part of the medial subdivision and gather their name from proximity to the obturator internus muscle
3. Internal iliac lymph nodes: surround the branches of the internal iliac vessels
  • Anterior, lateral sacral, and presacral subdivisions
    • hypogastric is a term used by some to describe the most cephalic of the internal iliac lymph nodes while others use the term to describe all internal iliac lymph nodes as a group
4. Inguinal lymph nodes: inferior to the inguinal ligament
  • Superficial subdivision nodes lie anterior to the inguinal ligament and femoral vessels
  • Deep subdivision lymph nodes are enclosed within the femoral sheath
5. Perivisceral nodes: include perirectal, periprostatic, perivesicular nodes

McMahon CJ, Rofsky NM, Pedrosa I. Lymphatic metastases from pelvic tumors: anatomic classification, characterization, and staging. Radiology 2010;254:31-46.

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