Contribution of flow cytometric analysis of endobronchial ultrasound-guided trans-bronchial needle aspiration specimens for diagnosis of mediastinal malignant lymphoma

<bold>Background:</bold> Endobronchial ultrasound-guided trans-bronchial needle aspiration(EBUS-TBNA) has been widely used for diagnosis of mediastinal lesions, including malignant lymphoma. Flow cytometry (FCM) is an essential complementary diagnostic analysis for lymphoma. However, it remains unclear whether FCM analysis can contribute to the diagnosis of mediastinal lymphoma because of the small size of TBNA samples. The present study aimed to clarify the diagnostic contribution of FCM analysis of EBUS-TBNA samples for malignant lymphoma. <bold>Methods:</bold> We retrospectively reviewed 23 consecutive lymphoma patients (8 diffuse large B-cell lymphoma; 3 follicular lymphoma; 6 other B-cell malignancies; 4 T-cell lymphoma; 2 Hodgkin lymphoma) who underwent EBUS-TBNA with FCM in our hospital from 2016 to 2023. <bold>Results:</bold> FCM analysis could be performed in 22 patients (95.6%). Eleven patients(47.8%) were successfully diagnosed by pathological examination of their EBUS-TBNA specimens only. Among the 12 patients whose TBNA pathology did not provide a definite diagnosis, FCM analysis led to a definite diagnosis in 8. Among the 17 patients with B-cell malignancies, monoclonality of the tumor cells was confirmed by FCM analysis of the kappa/lambda light chain ratio. <bold>Conclusions:</bold> FCM analysis is a useful complementary diagnostic method to EBUS-TBNA for mediastinal lymphoma.