MRI of a pathologic internal iliac lymph node in a patient with rectal cancer

Contrast-enhanced axial MRI image shows an abnormally enlarged internal iliac lymph node at initial diagnosis of rectal cancer (arrow). While this is a less common site of lymph node involvement from rectal cancer than is mesorectal lymphadenopathy, these are the only regional lymph nodes for rectal cancer that are not routinely excised during surgery. It is, therefore, crucial that abnormal nodes in this location be specifically recognized and managed in a multidisciplinary approach to treatment.