In this study, we do not provide data concerning potential causes that explain our observation and whether TTF-1 expression can, to a part, explain edema differences, yet it is tempting to speculate that TTF-1 may also be associated with a different tumor microenvironment (TME) in LUAD brain metastases which may relate to the observed differences in size of perifocal edema. Here, TTF1 is linked to neoplasm.