438 stases due to their low sensitivity (0-30%). Positron emis- sion tomography (PET) scanning can detect molecular changes as a result of metabolic changes found via the use of radiolabeled molecular probes that have different rates of cellular uptake. de Jong et al evaluated the tracer [11C]-choline with PET imaging in 67 prostate cancer pa- tients [17]. In 15 patients with biopsy-proven LN meta- stasis, the tracer had a sensitivity rate of 80% and a specific- ity rate of 96%. Another novel technique is high-resolution MRI used in tandem with the intravenous administration of lymphotropic superpara-magnetic nanoparticles, which potentially enables the identification of otherwise un- detectable LN disease. Among 80 patients with localized and locally advanced prostate cancer, this technique had a 90.5% sensitivity rate and a specificity rate of 97.8% com- pared with conventional MRI, which had a sensitivity rate of 35.4% and a specificity rate of 90.5% [18]. However, all false-negative nodes had a short-axis diameter of ＜5 mm when the sensitivity was only 41.1%. This promising tech- nique cannot be used for routine application and requires further clinical validation before its widespread use [18]. Initially, several studies reviewing the 111indium-labeled murine monoclonal antibody scan (ProstaScintTM scan) showed that this technique has superior sensitivity and specificity compared with CT scans [19,20]. However, in patients with a lower stage (mean PSA, 16 ng/ml), ProstaScintTM showed a very low positive predictive value (11%) and sensitivity (17%) for predicting LN invasion (LNI) [21]. 　The sentinel LN concept has in recent years been applied to prostate cancer and was first introduced by Wawroschek et al [22]. This concept has an apparent sensitivity rate of 96% for detecting lymphatic spread in node-positive pa- tients [23]. However, this technique has its drawbacks. Only nodes in close contact with the collimator can be detected. If these nodes are not directly accessible, there is a large chance of them being missed. 　In summary, [11C]-choline PET imaging or MRI with lymphotropic superpara-magnetic nanoparticles are prom- ising but are still currently under investigation for clinical use. At present, there is no accurate or reliable imaging mo- dality that can precisely detect LNI in prostate cancer patients. Thus, PLND represents the most accurate and re- liable staging procedure for the detection of LNI in prostate cancer. EXTENT OF PLND Anatomical studies have demonstrated that the prostate gland drains lymphatically into the periprostatic sub- capsular network; this has been confirmed by nuclear med- icine mapping studies [24-27]. For accurate diagnosis of no- dal metastasis and possible cure of nodal disease, several templates for PLND have been described [28,29]. The most commonly used template for PLND in prostate cancer in- cludes the removal of tissue along the external iliac vein and in the obturator fossa (Fig. 1) and is considered limited Korean J Urol 2011;52:437-445 Joung et al FIG. 1. Pelvic lymph node dissection field including the (1) external iliac node, (2) obturator node, and (3) internal iliac node. Reproduced with permission [32]. PLND (lPLND). The boundaries of the obturator fossa are the bladder (medially), the external iliac vein (laterally), the node of Cloquet (inferiorly), the bifurcation of the com- mon iliac (superiorly), and the obturator nerve (posterio- rly); these are collectively known as the external iliac nodes (diagram area 1). Standard PLND (sPLND) includes LNs in the obturator fossa and LNs deep and proximal to the obturator nerve (the obturator nodes; diagram area 2), whereas extended PLND (ePLND) also generally includes the tissue along the internal iliac vessels posteriorly (the internal iliac nodes; diagram area 3). Although some sur- geons include the additional removal of subaortic and pre- sacral nodes in their definition of ePLND [30,31], ePLND is most commonly considered to be a node dissection that involves bilateral resection of the external iliac, obturator, and internal iliac nodal groups (1, 2 and 3, respectively in Fig. 1) [32]. 　The total number of LNs removed during PLND is im- portant for maintaining the accuracy of the staging procedure. More extensive dissections result in a greater LN yield. Weingärtner et al compared nodal counts in ca- davers without prostate cancer subjected to PLND with ac- tual counts resected during radical prostatectomy and PLND [33] and reported that, on average, 20 LNs must be removed for pathologic analysis to ensure an adequate and representative sample. An ePLND that involves the re- moval of this volume of nodes provides enhanced accuracy as a staging procedure. An average LN yield of 21 nodes during ePLND was reported in one study [34], whereas an- other study described an ePLND template including pre- sacral and common iliac nodes in which the yield averaged 28 LNs [31]. 　To determine optimal templates of PLND in terms of ac- curate diagnosis and possible cure of nodal disease, many studies of pelvic LNs have been performed. Bader et al showed data for positive LN location following ePLND along the external iliac vein, obturator nerve, and internal iliac vessels in 365 patients [32,34]. The most common site