The internal iliac lymph nodes can be found adjacent to the internal iliac artery and its branches and drain the regions supplied by these vessels. This encompasses a large area from the genitalia anteriorly, the psoas muscle posteriorly and medial thigh inferiorly (see internal iliac artery for discussion of branches). The internal iliac lymph nodes lie posterior to the external iliac lymph nodes and can be split into four groups:
- anterior group: anterior to anterior branch of the internal iliac artery
- lateral sacral group: adjacent to the lateral sacral artery
- presacral group: anterior to the sacrum
- hypogastric group 2
Although spread to the external iliac nodes in malignancy occurs more frequently than the internal iliac nodes, some studies have demonstrated the incidence to be twice as high 3, the internal iliac lymph nodes are amongst the first nodes that malignancies within the pelvis spread to along with external iliac nodes. It is far more likely to see positive nodes in these areas than in the common iliac or para-aortic regions that are more proximal, and it is rare to have proximal positive nodes in the absence of nodes distally 4.
Under normal circumstances, it can be difficult to identify internal iliac nodes using CT/MRI as they are normally too small. Enlarged nodes with a diameter of 10mm or more along their shortest axis are deemed to be positive (in patients with malignancy), those with a diameter of between 5 and 10 mm are deemed to be suspicious 2.
- 1. Patterns of lymph node metastasis in locally advanced cervical cancer. Liu Z1, Hu K, Liu A, Shen J, Hou X, Lian X, Sun S, Yan J, Zhang F. Medicine (Baltimore). 2016 Sep;95(39)
- 2. McMinn's Clinical Atlas of Human Anatomy, 6th Edition, 2008
- 3. Lymphatic Metastases from Pelvic Tumors: Anatomic Classification, Characterization, and Staging Colm J. McMahon, MB, Neil M. Rofsky, MD, and Ivan Pedrosa, MD RSNA Radiology, Jan. 2010, Volume 254
- 4. Distribution patterns of metastatic pelvic lymph nodes assessed by CT/MRI in patients with uterine cervical cancer Goro Kasuya, Takafumi Toita, Kazuhisa Furutani, Takeshi Kodaira, Tatsuya Ohno, Yuko Kaneyasu, Ryouichi Yoshimura, Takashi Uno, Akira Yogi, Satoshi Ishikura, and Masahiro Hiraoka. Radiat Oncol. 2013; 8: 139.