Aquaporin-1 expression in fluoro-edenite-induced mesothelioma effusions: An approach by cell-block procedure

ObjectiveAquaporin 1 (AQP-1) is a water channel protein found in cell membranes, whose expression has been considered an independent favourable prognostic factor in pleural malignant mesothelioma (MM). The aim of this study was to evaluate the expression of AQP-1 and its prognostic value in a series of pleural MM effusions, from a geographical area with high concentrations of fluoro-edenite (FE). MethodsWe selected 25 MM cases from Biancavilla (Italy), an area with high environmental concentrations of FE. Cytological samples, cell-blocks (CB), clinical and follow-up data were available for all cases. Immunohistochemistry for calretinin, CK5/6, WT1, CK7 and TTF1 was used on CB sections to confirm the cytological diagnosis of MM. Immunohistochemistry for AQP-1 was performed and high expression was defined when 50% of tumour cells showed linear and circumferential membranous staining. ResultsThe cohort included 16 men and nine women (median age: 67.5years; range: 49-88years). The median survival was 14months (range 1.5-60months), with a significant value (P = 0.006). All cases have been histologically confirmed and classified as epithelioid (16 cases), biphasic (seven cases) and sarcomatoid (two cases). AQP-1 high expression has been observed in 16 cases. Comparing AQP-1 high expression to the survival of corresponding patients, a significant association with a slight increased overall survival of 12months has been demonstrated. Nine patients with a AQP-1 score less than 50% showed a shorter median overall survival (7months). ConclusionsAQP-1 high expression is detectable on cytological samples of FE-induced MM with a prognostic value. This study presents the first evaluation of the diagnostic usefulness and prognostic implications of aquaporin-1 (AQP-1) immunoexpression in pleural effusions of a rare group of patients with Fluoro-Edenite induced pleural malignant mesothelioma.