Atypia in Pleural Effusions after Lung Transplantation

Background: Pleural effusion cytology is challenging due to overlap between reactive and malignant processes. Pulmonary transplant patients are immunosuppressed, and at higher risk for both malignant and infectious conditions. This study evaluates atypia in pleural effusions from lung transplantation patients. Methods: All patients who underwent lung transplantation and had a post-transplant pleural fluid for cytologic examination were included. The initial cytologic interpretation was recorded, and the slides were reviewed for morphologic features. Follow-up clinical and pathologic information was recorded. Results: Of 240 lung transplant patients, 36 (15%) had a total of 63 pleural effusions. The median time from lung transplant to pleural effusion was 5 months; 33 (92%) were ipsilateral to a transplanted lung. The original cytologic diagnosis was negative for malignancy in 59 (94%) effusions, suspicious for a lymphoproliferative disorder in 3 effusions and suspicious for malignancy in 1 effusion. Reactive atypia was common, with prominent nucleoli in 24 cases (38%), but clusters of mesothelial cells were uncommon (25%), and community borders were only seen in 2 cases (3%). High cellularity of mesothelial-type cells was uncommon (6%). On follow-up, 4 patients were diagnosed with malignancy (1 metastatic adenocarcinoma, 2 PTLD, 1 pleural involvement by CLL/SLL). Effusions contralateral to the transplanted lung, the presence of clusters with community borders, and high mesothelial-type cellularity were most likely to be associated with malignancy. Conclusion: Reactive atypia is a frequent finding in the pleural effusions of patients after lung transplantation. Contralateral effusions or clusters with community borders should raise concern for malignancy.