Prognostic role of immune microenvironment in pleural metastases from breast and lung adenocarcinomas

Background: Pleural metastatic disease is a common disease with dismal prognosis. The immune microenvironment of metastatic pleural tissue remains largely unknown. Thus, we aimed to investigate the presence of different immune cell populations, and to compare them with clinical characteristics. Methods: We included 70 patients with lung and breast adenocarcinoma (ADC) diagnosed with pleural metastasis during a 2-year period with the primary endpoint to investigate if the main immune cell populations are present in pleural metastases and if they have any prognostic role. Secondary endpoints were to detect any differences in their presence between lung and breast primaries and to search for any correlation with the macroscopic (thoracoscopic) findings. We used immunohistochemical techniques for the detection of CD4(+), CD8(+), CD20(+), CD163(+) and S100(+) cells in whole tissue pleural biopsies of lung and breast metastases. Results: Primary endpoint: all these populations are present in the biopsies from lung and higher stromal and intratumoral CD4 counts, as well as higher stromal CD20 cells were positive prognostic factors for lung cancer metastases, while higher S100 intratumoral counts were positive prognostic factors in lung and marginally breast cancer metastases. Secondary endpoints: significant higher values for the stromal CD163 group (P=0.04) and for the intratumoral S100 group ( P=0.006) were seen in lung compared to breast metastases. Interesting correlations were also noted between thoracoscopic findings (nodules, masses, pachypleuritis) and the different factors studied. Conclusions: Our data show that the immune microenvironment may be important in this advanced tumoral setting and that possible targets of the nowadays numerous treatment strategies implicating the immune system may merit further exploration in this poor prognosis disease.