TOPIC: Procedures TYPE: Fellow Case Reports INTRODUCTION: Medical thoracoscopy is a minimally invasive method of obtaining pleural tissue for pathologic testing. While the use of a semi-rigid thoracoscope provides greater maneuverability over a rigid thoracoscope, the smaller working channel may limit the ability to obtain an adequate specimen using standard flexible forceps. CASE PRESENTATION: A 58-year-old male with a history of well-controlled HIV and sarcoidosis presented with a recurrent right pleural effusion. He underwent serial thoracenteses, which revealed a lymphocytic-predominant exudative effusion with triglycerides of 1,300 mg/dL consistent with chylothorax. However, cytology, pleural fluid and serologic testing, as well as lymphangiography failed to provide an underlying diagnosis. Given the uncertain etiology, the patient was consented for medical thoracoscopy. After being prepped and draped in the usual sterile fashion, the pleural space was entered with a semi-rigid thoracoscope. Visual inspection of the thoracic cavity did not reveal an obvious etiology of the pleural effusion or evidence of pleural metastases. Initially, large capacity flexible forceps (2.8mm - Boston Scientific) were used to obtain several specimens averaging 2mm x 4mm (Figure 1). Next, a section of parietal pleura was identified and using an electrocautery knife (HookKnife – Olympus), a 4mm by 10mm full-thickness section was dissected and removed en bloc. This piece was then retrieved with forceps and sent for pathologic testing. The site of the electrocautery biopsy was observed and did not show any evidence of active bleeding (Figure 2). A chest tube was left in place for ongoing management of the patient's pleural effusion. The patient tolerated the procedure well without complications and is awaiting final pathologic diagnosis. DISCUSSION: We describe the integration of a flexible electrocautery knife into semi-rigid medical thoracoscopy. This technique allows for larger specimens of intact pleural tissue to be obtained than would otherwise be possible with a standard flexible forceps biopsy. CONCLUSIONS: The use of electrocautery as a biopsy tool during semi-rigid thoracoscopy provides an effective means of acquiring full-thickness pleural samples and helps to mitigate the disadvantages of a smaller working channel when compared to rigid thoracoscopy. REFERENCE #1: Canto A, et al. Points to consider when choosing a biopsy method in cases of pleurisy of unknown origin. Chest. 1983 Aug;84(2):176-9. doi: 10.1378/chest.84.2.176. PMID: 6872597. DISCLOSURES: Consultant relationship with medtronic Please note: 2019-2021 Added 04/27/2021 by George Cheng, source=Web Response, value=Consulting fee Consultant relationship with boston scientific Please note: 2019-2021 Added 04/27/2021 by George Cheng, source=Web Response, value=Consulting fee Consultant relationship with pinnicle biologics Please note: 2019-2021 Added 04/28/2021 by George Cheng, source=Web Response, value=Consulting Owner/Founder relationship with restor3D Please note: 2016-present Added 04/28/2021 by George Cheng, source=Web Response, value=Ownership interest Consultant relationship with Intuitive Surgical Please note: 2019-2021 Added 04/28/2021 by George Cheng, source=Web Response, value=Consulting fee No relevant relationships by Russell Miller, source=Web Response No relevant relationships by Matthew Nobari, source=Web Response No relevant relationships by Alex Pearce, source=Web Response No relevant relationships by Grant Senyei, source=Web Response