Characterization of the Immune Landscapes of Malignant Pleural Effusions and Their Corresponding Primary Tumors from Patients with Breast Carcinoma or Lung Adenocarcinoma

Background: Malignant pleural effusion (MPE),a frequent complication of advanced malignancies. This pilot study characterized and compared the immune landscapes of breast carcinoma (BC) and lung adenocarcinoma (LADC) primary tumors(PTs) and their corresponding MPEs and tested the incorporation of multiplexed image technology for the study of malignant fluids. Methods: We studied the immune contexture of 6 BC and 5 LADC PT samples and their MPEs using 3 multiplex immunofluorescence panels. We explored associations between sample characteristics and pleural effusion–free survival. Results: Although we found 3 out of 11 PTs PD-L1 positive more than 1% by malignant cells, no MPE samples reached positive expression by malignant cells. In addition, CD3+ T cells and CD3+CD8+ cytotoxic T cells predominated (median percentages for MPEs vs. PTs: 45.5% vs. 40.7% and 4.7% vs. 6.6%, respectively). In the BC samples, CD68+ macrophages predominated (median percentages for MPEs vs. PTs:61% vs. 57.1%). Generally, CD3+CD8+FOXP3+ T cells in PTs and the distances from the malignant cells to CD3+CD8+Ki67+ and CD3+PD-1+ T cells were correlated in the first event of MPE after diagnosis. Conclusions: The immune cell phenotypes in the MPEs and PTs were similar within each cancer type but were different for LADC vs. BC.MPE analysis could be used as a substitute for PT analysis, but an expanded study on this topic is essential.