PECAM1 and lung cancer: Consistent with published observations in lung cancer [19], CD31-immunostained tumor sections revealed the presence of three distinct vascular phenotypes across the six PDX models: A tumor vessel (TV) phenotype in which blood vessels were distributed throughout the tumor (01541, 01752), a stromal vessel (SV) phenotype in which a majority of the vessels (red arrows) were restricted to the infiltrating stroma (black arrows) surrounding the tumor cells (01706, 18243), and a mixed vessel phenotype that showed CD31+ vessels in the stroma and between islands of tumor cells (01795, 01769).