Extramammary Paget's Disease With Bilateral Sentinel Lymph Node Biopsy: a Multicenter Study of Lymphatic Patterns and Outcomes.

BACKGROUND

Extramammary Paget's disease (EMPD) can metastasize to lymph nodes or distant sites. Sentinel lymph node biopsy (SLNB) is recommended for invasive EMPD without clinical nodal involvement.

OBJECTIVES

Lesions near or across the midline may show bilateral lymphatic drainage, but the clinical significance of bilateral SLNB remains unclear. This study evaluated SLN metastatic distribution and its association with clinicopathological features, lymphatic drainage patterns, and survival in patients undergoing bilateral SLNB.

METHODS

We retrospectively reviewed 147 patients with EMPD who underwent bilateral SLNB at three institutions between 2015 and 2025. Tumor characteristics, SLN status, recurrence, and survival outcomes were analyzed. Patients were stratified as bilateral negative, unilateral positive, or bilateral positive. Clinicopathological features, lymphatic drainage patterns, and survival outcomes, including overall survival (OS), recurrence-free survival (RFS), and disease-free survival (DFS), were compared.

RESULTS

Bilateral SLN positivity was detected in eight male patients with genital nodular lesions; unilateral positivity occurred in 12 patients, and 127 were bilaterally negative. Contralateral SLNs were frequently negative despite lesions crossing the midline, although bilateral metastases developed in two patients. Four ectopic lower abdominal lesions were identified, two with irregular drainage. Patients with bilaterally negative SLNs had significantly better survival than those with SLN metastases. No significant differences in RFS or DFS were observed between the unilateral- and bilateral-positive groups.

CONCLUSIONS

Bilateral SLN positivity is rare and limited to male genital cases. It was not associated with worse disease-related outcomes than unilateral positivity. Risk of bilateral metastasis appears to depend more on tumor location than intrinsic aggressiveness.