Ho, Thai H.

536 Background: The management of malignant mesothelioma of the tunica vaginalis of the testes (MMTVT) is not clearly defined, though retroperitoneal lymph node dissection has been reported as a diagnostic and potentially therapeutic option. Herein we present our experience with robot assisted retroperitoneal lymph node dissection (RARPLND) in a series of patients with MMTVT. Methods: The Mayo Clinic cancer registry was queried from 1972-present for all patients who had a diagnosis of MMTVT. Six patients were identified, five of whom were treated with RPLND, where four underwent RARPLND. Data was collected on pertinent demographic, preoperative, perioperative, postoperative outcomes and follow-up oncological data. Results: In five patients who underwent RPLND, the median age was 50 years (IQR 34-51), median BMI was 26.9 (IQR 26.4-30.6). Four patients originally presented with right sided symptomatic hydroceles, while one presented with right sided chronic epididymitis. Orchiectomy (one simple, two inguinal radical) was performed in three patients and hydrocelectomy in the other two patients prior to presentation. Preoperative cross-sectional imaging, including PET-CT scan in three patients, was negative for lymphadenopathy or metastasis. RARPLND was performed in 4/5 (80%) cases and concomitant hemiscrotectomy in 4/5 (80%) cases. Full bilateral template was performed in three patients and right modified template was performed in the remaining two. Median lymph node yield was 29 (IQR 22-32) and median blood loss was 275 cc (IQR 200-300). Positive retroperitoneal lymph nodes were found in 3/5 (60%) cases. Final margins of hemiscrotectomy were negative in all four cases. All patients who underwent RARPLND were discharged home on postoperative day one. One patient received four cycles of adjuvant Cisplatin and Pemetrexed. Mean follow-up was 27 months (range 2-47). No patients recurred. Conclusions: MMTVT is a very rare malignancy with high potential for retroperitoneal lymph node dissemination. Regardless of the approach, RPLND may provide both a diagnostic and therapeutic benefit, with the robotic approach affording a potentially expedited recovery.