Lymph nodes >1 cm in short axis are highly suspicious for metastatic disease, particularly if they are located in the hilar regions of the kidney or in the para-aortic or caval areas (eg, testicular cancer landing zones). Various studies have established the accuracy of CT in detecting metastatic retroperitoneal lymph nodes from testicular cancer, which ranges from 73% to 97%, sensitivity ranges from 65% to 96%, and specificity from 81% to 100% [7,17-22]. Data also indicate that the accuracy of CT declines in patients with limited disease (eg, stage N1 and stage N2) and also if the upper limit of normal lymph node size is lowered [15,17,21]. Of note, most of these studies are relatively old and were performed using single-slice CT; however, limited newer data suggest similar accuracy using multi- slice CT compared with single-slice CT [23]. It is important to recognize that a significant percentage of metastatic lymph nodes will be <1 cm, up to 60% in one series [24]. For this reason, some authors suggest using a cut-off value of 0.7 cm to 0.8 cm in testicular cancer at the expense of reduced specificity [24,25]. These cut-off values are for the short-axis measurement when assessing the likelihood of nodal disease (N0 versus N1 disease); however, when assessing the nodal burden, the lymph nodes should be measured in long axis (eg, N1 versus N2 and N3 disease) [6,25]. Two studies have also evaluated the value of nodal craniocaudal length or volume as risk factors for recurrence in testicular cancer [26,27]. Another study comparing lymph node measurements performed by expert radiologists, other observers, and a semiautomated process showed excellent correlation between measurements, indicating that the task of actually measuring lymph nodes, which can be time consuming and tedious, could potentially be delegated or automated in the future [28].
Staging and Surveillance of Testicular Cancer. Lymph nodes >1 cm in short axis are highly suspicious for metastatic disease, particularly if they are located in the hilar regions of the kidney or in the para-aortic or caval areas (eg, testicular cancer landing zones). Various studies have established the accuracy of CT in detecting metastatic retroperitoneal lymph nodes from testicular cancer, which ranges from 73% to 97%, sensitivity ranges from 65% to 96%, and specificity from 81% to 100% [7,17-22]. Data also indicate that the accuracy of CT declines in patients with limited disease (eg, stage N1 and stage N2) and also if the upper limit of normal lymph node size is lowered [15,17,21]. Of note, most of these studies are relatively old and were performed using single-slice CT; however, limited newer data suggest similar accuracy using multi- slice CT compared with single-slice CT [23]. It is important to recognize that a significant percentage of metastatic lymph nodes will be <1 cm, up to 60% in one series [24]. For this reason, some authors suggest using a cut-off value of 0.7 cm to 0.8 cm in testicular cancer at the expense of reduced specificity [24,25]. These cut-off values are for the short-axis measurement when assessing the likelihood of nodal disease (N0 versus N1 disease); however, when assessing the nodal burden, the lymph nodes should be measured in long axis (eg, N1 versus N2 and N3 disease) [6,25]. Two studies have also evaluated the value of nodal craniocaudal length or volume as risk factors for recurrence in testicular cancer [26,27]. Another study comparing lymph node measurements performed by expert radiologists, other observers, and a semiautomated process showed excellent correlation between measurements, indicating that the task of actually measuring lymph nodes, which can be time consuming and tedious, could potentially be delegated or automated in the future [28].