(401) Magnetic Sentinel Node Biopsy with Sienna+®/SentiMag® in Penile Squamous Cell Carcinoma: A Feasible Radiation-Free Alternative

Introduction Penile squamous cell carcinoma (SCC) is a rare but aggressive malignancy in which accurate inguinal lymph node staging is essential for prognosis, management, and potential preservation of penile function. Dynamic sentinel lymph node biopsy (DSNB) using technetium-99m radiotracers and blue dye is the gold standard, but its use is limited by reliance on nuclear medicine facilities, complex logistics, and exposure to ionizing radiation. Magnetic tracers such as Sienna+® (superparamagnetic iron oxide nanoparticles), detected with the SentiMag® magnetometer, represent a radiation-free alternative that may facilitate sentinel node detection, particularly in centers without access to nuclear medicine. Objective To assess the feasibility and clinical performance of sentinel lymph node biopsy (SLNB) using Sienna+®/SentiMag® combined with methylene blue in penile SCC. Methods A 62-year-old man with a poorly differentiated (G3), HPV-negative penile SCC (cN0) underwent glansectomy with SLNB. The magnetic tracer Sienna+® was injected perilesionally 24 hours before surgery. Intraoperative sentinel node detection was performed with the SentiMag® handheld magnetometer and methylene blue dye. Surgical findings, histopathology, and short-term postoperative outcomes were evaluated. Results Two sentinel nodes were identified and excised: one in the right groin, detected by both SentiMag® (700 units) and methylene blue, and one in the left groin, detected exclusively by SentiMag® (3000 units). Histopathology confirmed pT1b disease with perineural invasion, no lymphovascular invasion, negative surgical margins, and no nodal metastases (pN0). Final staging was pT1b pN0 R0. Postoperative recovery was initially uneventful; however, the patient was readmitted with right-sided orchitis and sepsis, which resolved with antibiotics. At one-month follow-up, wound healing was satisfactory, catheter was removed, and no clinical evidence of recurrence or nodal disease was observed. Conclusions Magnetic SLNB with Sienna+®/SentiMag® is feasible and safe in penile SCC. Notably, it identified a sentinel node not detected by methylene blue, suggesting potential for improved sensitivity. This radiation-free technique offers logistical and safety advantages over conventional DSNB, particularly in centers without nuclear medicine access. By enabling more accurate nodal staging, it may reduce the need for extensive lymphadenectomy, potentially minimizing morbidity and contributing indirectly to the preservation of penile function. Limitations such as MRI artifacts and susceptibility to interference from metallic instruments remain. Larger prospective studies are needed to validate diagnostic accuracy and establish its role in routine clinical practice. Disclosure No