Regional lymph node mapping in patients with penile cancer undergoing radical inguinal lymph node dissection——retrospective cohort study

Background: Radical inguinal lymph node dissection (rILND) is the most available treatment to cure penile cancer (PC) with limited inguinal-confined disease. However, guidelines regarding acceptable boundaries of rILND are controversial, and consensus is lacking. We aimed to standardize the surgical boundaries of rILND with definite pathological evidence and explore the distribution pattern of inguinal lymph nodes (ILNs) in PC. Methods: A total of 414 PC patients from two centers who underwent rILND were enrolled. The ILN distribution was divided into seven zones anatomically for pathological examination. Student’s t test and Kaplan‒Meier survival analysis were used. Results: ILNs displayed a funnel-shaped distribution with high density in superior regions. ILNs and metastatic nodes present anywhere within the radical boundaries. Positive ILNs were mainly concentrated in zone I (51.7%) and zone II (41.3%), but there were 8.7 and 12.3% in inferior zones V and VI, respectively, and 7.1% in the deep ILNs. More importantly, a single positive ILN and first-station positive zone was detected in all seven regions. Single positive ILNs were located in zones I through VI in 40.4%, 23.6%, 6.7%, 18.0%, 4.5% and 1.1%, respectively, and 5.6% presented deep ILN metastasis directly. Conclusion: We established a detailed ILN distribution map and displayed lymphatic drainage patterns with definite pathological evidence using a large cohort of PC patients. Single positive ILNs and first-station metastatic zones were observed in any region, even directly with deep ILN metastasis. Only rILND can ensure tumor-free resection without the omission of positive nodes.