Background: Patients with primary mediastinal lymphomas frequently present with a residual mass after completion of first-line therapy. Although a positron emission tomography scan is usually recommended, it fails to distinguish between persistent lymphoma and inflammation. Although percutaneous biopsy may have a high diagnostic yield for the initial diagnosis of mediastinal lymphomas, this biopsy has poor accuracy for detecting persistent disease in a residual mass given the heterogeneity of these residual masses. Because persistent disease has important therapeutic implications, we evaluated the role of operative biopsy in detecting lymphoma in the residual mass. Methods: Between 2009 and 2015, consecutive patients (n = 77) undergoing tissue biopsy for initial diagnosis as well as for a positron emission tomography-positive residual mass were included. Tissue biopsy for a residual mass was repeated until frozen section was diagnostic or at least the mass on the ipsilateral hemi-mediastinum was resected. Results: Of the initial 77 patients, 34 underwent operative restaging for a residual mass after chemotherapy, while 43 had a complete response. In these 34 patients, operative biopsy revealed the presence of lymphoma in 53%, predominantly Hodgkin's disease and diffuse large B-cell lymphoma. There was no significant difference in tumor volume (51% versus 39%) and a decrease in the positron emission tomography-standardized uptake valuemax (68% vs 60%) in patients with or those without persistent lymphoma. There were no surgical complications and the duration of stay for all patients undergoing thoracoscopy was <24 hours. Residual lymphoma was treated with second-line therapy guided by the pathologic analysis. Conclusion: A large proportion of patients with residual positron emission tomography-avidity after first-line chemotherapy of mediastinal lymphomas have residual disease that can be detected safely using minimally invasive thoracoscopy.
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